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swift-mirror/lib/Sema/CSDiag.cpp

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//===--- CSDiag.cpp - Constraint Diagnostics ------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
//
// This file implements diagnostics for the type checker.
//
//===----------------------------------------------------------------------===//
#include "CSDiag.h"
#include "CSDiagnostics.h"
#include "CalleeCandidateInfo.h"
#include "ConstraintSystem.h"
#include "MiscDiagnostics.h"
#include "TypeCheckAvailability.h"
#include "TypoCorrection.h"
#include "swift/AST/ASTWalker.h"
#include "swift/AST/DiagnosticEngine.h"
#include "swift/AST/GenericEnvironment.h"
#include "swift/AST/Initializer.h"
#include "swift/AST/ParameterList.h"
#include "swift/AST/ProtocolConformance.h"
#include "swift/AST/TypeMatcher.h"
#include "swift/AST/TypeWalker.h"
#include "swift/Basic/Defer.h"
#include "swift/Basic/StringExtras.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/SaveAndRestore.h"
using namespace swift;
using namespace constraints;
namespace swift {
Type replaceTypeParametersWithUnresolved(Type ty) {
if (!ty) return ty;
if (!ty->hasTypeParameter() && !ty->hasArchetype()) return ty;
auto &ctx = ty->getASTContext();
return ty.transform([&](Type type) -> Type {
if (type->is<ArchetypeType>() ||
type->isTypeParameter())
return ctx.TheUnresolvedType;
return type;
});
}
Type replaceTypeVariablesWithUnresolved(Type ty) {
if (!ty) return ty;
if (!ty->hasTypeVariable()) return ty;
auto &ctx = ty->getASTContext();
return ty.transform([&](Type type) -> Type {
if (type->isTypeVariableOrMember())
return ctx.TheUnresolvedType;
return type;
});
}
};
static bool isUnresolvedOrTypeVarType(Type ty) {
return ty->isTypeVariableOrMember() || ty->is<UnresolvedType>();
}
/// Flags that can be used to control name lookup.
enum TCCFlags {
/// Allow the result of the subexpression to be an lvalue. If this is not
/// specified, any lvalue will be forced to be loaded into an rvalue.
TCC_AllowLValue = 0x01,
/// Re-type-check the given subexpression even if the expression has already
/// been checked already. The client is asserting that infinite recursion is
/// not possible because it has relaxed a constraint on the system.
TCC_ForceRecheck = 0x02,
/// tell typeCheckExpression that it is ok to produce an ambiguous result,
/// it can just fill in holes with UnresolvedType and we'll deal with it.
TCC_AllowUnresolvedTypeVariables = 0x04
};
using TCCOptions = OptionSet<TCCFlags>;
inline TCCOptions operator|(TCCFlags flag1, TCCFlags flag2) {
return TCCOptions(flag1) | flag2;
}
namespace {
/// If a constraint system fails to converge on a solution for a given
/// expression, this class can produce a reasonable diagnostic for the failure
/// by analyzing the remnants of the failed constraint system. (Specifically,
/// left-over inactive, active and failed constraints.)
/// This class does not tune its diagnostics for a specific expression kind,
/// for that, you'll want to use an instance of the FailureDiagnosis class.
class FailureDiagnosis :public ASTVisitor<FailureDiagnosis, /*exprresult*/bool>{
friend class ASTVisitor<FailureDiagnosis, /*exprresult*/bool>;
Expr *expr = nullptr;
ConstraintSystem &CS;
public:
FailureDiagnosis(Expr *expr, ConstraintSystem &cs) : expr(expr), CS(cs) {
assert(expr);
}
template<typename ...ArgTypes>
InFlightDiagnostic diagnose(ArgTypes &&...Args) {
return CS.getASTContext().Diags.diagnose(std::forward<ArgTypes>(Args)...);
}
/// Unless we've already done this, retypecheck the specified child of the
/// current expression on its own, without including any contextual
/// constraints or the parent expr nodes. This is more likely to succeed than
/// type checking the original expression.
///
/// This mention may only be used on immediate children of the current expr
/// node, because ClosureExpr parameters need to be treated specially.
///
/// This can return a new expression (for e.g. when a UnresolvedDeclRef gets
/// resolved) and returns null when the subexpression fails to typecheck.
///
Expr *typeCheckChildIndependently(
Expr *subExpr, Type convertType = Type(),
ContextualTypePurpose convertTypePurpose = CTP_Unused,
TCCOptions options = TCCOptions(),
ExprTypeCheckListener *listener = nullptr,
bool allowFreeTypeVariables = true);
Expr *typeCheckChildIndependently(Expr *subExpr, TCCOptions options,
bool allowFreeTypeVariables = true) {
return typeCheckChildIndependently(subExpr, Type(), CTP_Unused, options,
nullptr, allowFreeTypeVariables);
}
Type getTypeOfTypeCheckedChildIndependently(Expr *subExpr,
TCCOptions options = TCCOptions()) {
auto e = typeCheckChildIndependently(subExpr, options);
return e ? CS.getType(e) : Type();
}
/// Find a nearest declaration context which could be used
/// to type-check this sub-expression.
DeclContext *findDeclContext(Expr *subExpr) const;
/// Special magic to handle inout exprs and tuples in argument lists.
Expr *typeCheckArgumentChildIndependently(Expr *argExpr, Type argType,
const CalleeCandidateInfo &candidates,
TCCOptions options = TCCOptions());
void getPossibleTypesOfExpressionWithoutApplying(
Expr *&expr, DeclContext *dc, SmallPtrSetImpl<TypeBase *> &types,
FreeTypeVariableBinding allowFreeTypeVariables =
FreeTypeVariableBinding::Disallow,
ExprTypeCheckListener *listener = nullptr) {
TypeChecker::getPossibleTypesOfExpressionWithoutApplying(
expr, dc, types, allowFreeTypeVariables, listener);
CS.cacheExprTypes(expr);
}
Type getTypeOfExpressionWithoutApplying(
Expr *&expr, DeclContext *dc, ConcreteDeclRef &referencedDecl,
FreeTypeVariableBinding allowFreeTypeVariables =
FreeTypeVariableBinding::Disallow,
ExprTypeCheckListener *listener = nullptr) {
auto type =
TypeChecker::getTypeOfExpressionWithoutApplying(expr, dc,
referencedDecl,
allowFreeTypeVariables,
listener);
CS.cacheExprTypes(expr);
return type;
}
/// Diagnose common failures due to applications of an argument list to an
/// ApplyExpr or SubscriptExpr.
bool diagnoseParameterErrors(CalleeCandidateInfo &CCI,
Expr *fnExpr, Expr *argExpr,
ArrayRef<Identifier> argLabels);
/// Attempt to diagnose a specific failure from the info we've collected from
/// the failed constraint system.
bool diagnoseExprFailure();
/// Emit an ambiguity diagnostic about the specified expression.
void diagnoseAmbiguity(Expr *E);
/// Attempt to produce a diagnostic for a mismatch between an expression's
/// type and its assumed contextual type.
bool diagnoseContextualConversionError(Expr *expr, Type contextualType,
ContextualTypePurpose CTP,
Type suggestedType = Type());
bool diagnoseImplicitSelfErrors(Expr *fnExpr, Expr *argExpr,
CalleeCandidateInfo &CCI,
ArrayRef<Identifier> argLabels);
private:
/// Validate potential contextual type for type-checking one of the
/// sub-expressions, usually correct/valid types are the ones which
/// either don't have type variables or are not generic, because
/// generic types with left-over type variables or unresolved types
/// degrade quality of diagnostics if allowed to be used as contextual.
///
/// \param contextualType The candidate contextual type.
/// \param CTP The contextual purpose attached to the given candidate.
///
/// \returns Pair of validated type and it's purpose, potentially nullified
/// if it wasn't an appropriate type to be used.
std::pair<Type, ContextualTypePurpose>
validateContextualType(Type contextualType, ContextualTypePurpose CTP);
/// Check the specified closure to see if it is a multi-statement closure with
/// an uninferred type. If so, diagnose the problem with an error and return
/// true.
bool diagnoseAmbiguousMultiStatementClosure(ClosureExpr *closure);
/// Given a result of name lookup that had no viable results, diagnose the
/// unviable ones.
void diagnoseUnviableLookupResults(MemberLookupResult &lookupResults,
Expr *expr, Type baseObjTy, Expr *baseExpr,
DeclNameRef memberName,
DeclNameLoc nameLoc, SourceLoc loc);
bool diagnoseMemberFailures(
Expr *E, Expr *baseEpxr, ConstraintKind lookupKind,
DeclNameRef memberName, FunctionRefKind funcRefKind,
ConstraintLocator *locator,
Optional<std::function<bool(ArrayRef<OverloadChoice>)>> callback = None,
bool includeInaccessibleMembers = true);
bool diagnoseSubscriptErrors(SubscriptExpr *SE, bool performingSet);
bool visitExpr(Expr *E);
bool visitIdentityExpr(IdentityExpr *E);
bool visitTryExpr(TryExpr *E);
bool visitUnresolvedMemberExpr(UnresolvedMemberExpr *E);
bool visitUnresolvedDotExpr(UnresolvedDotExpr *UDE);
bool visitArrayExpr(ArrayExpr *E);
bool visitDictionaryExpr(DictionaryExpr *E);
bool visitObjectLiteralExpr(ObjectLiteralExpr *E);
bool visitSubscriptExpr(SubscriptExpr *SE);
bool visitApplyExpr(ApplyExpr *AE);
bool visitCoerceExpr(CoerceExpr *CE);
bool visitIfExpr(IfExpr *IE);
bool visitRebindSelfInConstructorExpr(RebindSelfInConstructorExpr *E);
};
} // end anonymous namespace
/// Given a result of name lookup that had no viable results, diagnose the
/// unviable ones.
void FailureDiagnosis::diagnoseUnviableLookupResults(
MemberLookupResult &result, Expr *E, Type baseObjTy, Expr *baseExpr,
DeclNameRef memberName, DeclNameLoc nameLoc, SourceLoc loc) {
SourceRange baseRange = baseExpr ? baseExpr->getSourceRange() : SourceRange();
// If we found no results at all, mention that fact.
if (result.UnviableCandidates.empty()) {
MissingMemberFailure failure(CS, baseObjTy, memberName,
CS.getConstraintLocator(E));
auto diagnosed = failure.diagnoseAsError();
assert(diagnosed && "Failed to produce missing member diagnostic");
(void)diagnosed;
return;
}
// Otherwise, we have at least one (and potentially many) viable candidates
// sort them out. If all of the candidates have the same problem (commonly
// because there is exactly one candidate!) diagnose this.
auto firstProblem = result.UnviableReasons[0];
bool sameProblem = llvm::all_of(
result.UnviableReasons,
[&firstProblem](const MemberLookupResult::UnviableReason &problem) {
return problem == firstProblem;
});
auto instanceTy = baseObjTy;
if (auto *MTT = instanceTy->getAs<AnyMetatypeType>())
instanceTy = MTT->getInstanceType();
if (sameProblem) {
// If the problem is the same for all of the choices, let's
// just pick one which has a declaration.
auto choice = llvm::find_if(
result.UnviableCandidates,
[&](const OverloadChoice &choice) { return choice.isDecl(); });
// This code can't currently diagnose key path application
// related failures.
if (!choice)
return;
switch (firstProblem) {
case MemberLookupResult::UR_WritableKeyPathOnReadOnlyMember:
case MemberLookupResult::UR_ReferenceWritableKeyPathOnMutatingMember:
case MemberLookupResult::UR_KeyPathWithAnyObjectRootType:
break;
case MemberLookupResult::UR_UnavailableInExistential: {
InvalidMemberRefOnExistential failure(
CS, instanceTy, memberName, CS.getConstraintLocator(E));
failure.diagnoseAsError();
return;
}
case MemberLookupResult::UR_InstanceMemberOnType:
case MemberLookupResult::UR_TypeMemberOnInstance: {
auto locatorKind = isa<SubscriptExpr>(E)
? ConstraintLocator::SubscriptMember
: ConstraintLocator::Member;
AllowTypeOrInstanceMemberFailure failure(
CS, baseObjTy, choice->getDecl(), memberName,
CS.getConstraintLocator(E, locatorKind));
auto diagnosed = failure.diagnoseAsError();
assert(diagnosed &&
"Failed to produce missing or extraneous metatype diagnostic");
(void)diagnosed;
return;
}
case MemberLookupResult::UR_MutatingMemberOnRValue:
case MemberLookupResult::UR_MutatingGetterOnRValue: {
MutatingMemberRefOnImmutableBase failure(CS, choice->getDecl(),
CS.getConstraintLocator(E));
(void)failure.diagnose();
return;
}
case MemberLookupResult::UR_Inaccessible: {
// FIXME: What if the unviable candidates have different levels of access?
//
// If we found an inaccessible member of a protocol extension, it might
// be declared 'public'. This can only happen if the protocol is not
// visible to us, but the conforming type is. In this case, we need to
// clamp the formal access for diagnostics purposes to the formal access
// of the protocol itself.
InaccessibleMemberFailure failure(CS, choice->getDecl(),
CS.getConstraintLocator(E));
auto diagnosed = failure.diagnoseAsError();
assert(diagnosed && "failed to produce expected diagnostic");
for (auto cand : result.UnviableCandidates) {
if (!cand.isDecl())
continue;
auto *candidate = cand.getDecl();
// failure is going to highlight candidate given to it,
// we just need to handle the rest here.
if (candidate != choice->getDecl())
diagnose(candidate, diag::decl_declared_here,
candidate->getFullName());
}
return;
}
}
}
// Otherwise, we don't have a specific issue to diagnose. Just say the vague
// 'cannot use' diagnostic.
if (!baseObjTy->isEqual(instanceTy))
diagnose(loc, diag::could_not_use_type_member,
instanceTy, memberName)
.highlight(baseRange).highlight(nameLoc.getSourceRange());
else
diagnose(loc, diag::could_not_use_value_member,
baseObjTy, memberName)
.highlight(baseRange).highlight(nameLoc.getSourceRange());
return;
}
namespace {
class ExprTypeSaverAndEraser {
llvm::DenseMap<Expr*, Type> ExprTypes;
llvm::DenseMap<TypeLoc*, Type> TypeLocTypes;
llvm::DenseMap<Pattern*, Type> PatternTypes;
llvm::DenseMap<ParamDecl*, Type> ParamDeclInterfaceTypes;
ExprTypeSaverAndEraser(const ExprTypeSaverAndEraser&) = delete;
void operator=(const ExprTypeSaverAndEraser&) = delete;
public:
ExprTypeSaverAndEraser(Expr *E) {
struct TypeSaver : public ASTWalker {
ExprTypeSaverAndEraser *TS;
TypeSaver(ExprTypeSaverAndEraser *TS) : TS(TS) {}
std::pair<bool, Expr *> walkToExprPre(Expr *expr) override {
TS->ExprTypes[expr] = expr->getType();
SWIFT_DEFER {
assert((!expr->getType() || !expr->getType()->hasTypeVariable()
// FIXME: We shouldn't allow these, either.
|| isa<LiteralExpr>(expr)) &&
"Type variable didn't get erased!");
};
// Preserve module expr type data to prevent further lookups.
if (auto *declRef = dyn_cast<DeclRefExpr>(expr))
if (isa<ModuleDecl>(declRef->getDecl()))
return { false, expr };
// Don't strip type info off OtherConstructorDeclRefExpr, because
// CSGen doesn't know how to reconstruct it.
if (isa<OtherConstructorDeclRefExpr>(expr))
return { false, expr };
// If a literal has a Builtin.Int or Builtin.FP type on it already,
// then sema has already expanded out a call to
// Init.init(<builtinliteral>)
// and we don't want it to make
// Init.init(Init.init(<builtinliteral>))
// preserve the type info to prevent this from happening.
if (isa<LiteralExpr>(expr) && !isa<InterpolatedStringLiteralExpr>(expr) &&
!(expr->getType() && expr->getType()->hasError()))
return { false, expr };
// If a ClosureExpr's parameter list has types on the decls, then
// remove them so that they'll get regenerated from the
// associated TypeLocs or resynthesized as fresh typevars.
if (auto *CE = dyn_cast<ClosureExpr>(expr))
for (auto P : *CE->getParameters()) {
if (P->hasInterfaceType()) {
TS->ParamDeclInterfaceTypes[P] = P->getInterfaceType();
P->setInterfaceType(Type());
}
}
expr->setType(nullptr);
return { true, expr };
}
// If we find a TypeLoc (e.g. in an as? expr), save and erase it.
bool walkToTypeLocPre(TypeLoc &TL) override {
if (TL.getTypeRepr() && TL.getType()) {
TS->TypeLocTypes[&TL] = TL.getType();
TL.setType(Type());
}
return true;
}
std::pair<bool, Pattern*> walkToPatternPre(Pattern *P) override {
if (P->hasType()) {
TS->PatternTypes[P] = P->getType();
P->setType(Type());
}
return { true, P };
}
// Don't walk into statements. This handles the BraceStmt in
// non-single-expr closures, so we don't walk into their body.
std::pair<bool, Stmt *> walkToStmtPre(Stmt *S) override {
return { false, S };
}
};
E->walk(TypeSaver(this));
}
void restore() {
for (auto exprElt : ExprTypes)
exprElt.first->setType(exprElt.second);
for (auto typelocElt : TypeLocTypes)
typelocElt.first->setType(typelocElt.second);
for (auto patternElt : PatternTypes)
patternElt.first->setType(patternElt.second);
for (auto paramDeclIfaceElt : ParamDeclInterfaceTypes) {
assert(!paramDeclIfaceElt.first->isImmutable() ||
!paramDeclIfaceElt.second->is<InOutType>());
paramDeclIfaceElt.first->setInterfaceType(paramDeclIfaceElt.second->getInOutObjectType());
}
// Done, don't do redundant work on destruction.
ExprTypes.clear();
TypeLocTypes.clear();
PatternTypes.clear();
}
// On destruction, if a type got wiped out, reset it from null to its
// original type. This is helpful because type checking a subexpression
// can lead to replacing the nodes in that subexpression. However, the
// failed ConstraintSystem still has locators pointing to the old nodes,
// and if expr-specific diagnostics fail to turn up anything useful to say,
// we go digging through failed constraints, and expect their locators to
// still be meaningful.
~ExprTypeSaverAndEraser() {
for (auto exprElt : ExprTypes)
if (!exprElt.first->getType())
exprElt.first->setType(exprElt.second);
for (auto typelocElt : TypeLocTypes)
if (!typelocElt.first->getType())
typelocElt.first->setType(typelocElt.second);
for (auto patternElt : PatternTypes)
if (!patternElt.first->hasType())
patternElt.first->setType(patternElt.second);
for (auto paramDeclIfaceElt : ParamDeclInterfaceTypes)
if (!paramDeclIfaceElt.first->hasInterfaceType()) {
paramDeclIfaceElt.first->setInterfaceType(
getParamBaseType(paramDeclIfaceElt));
}
}
private:
static Type getParamBaseType(std::pair<ParamDecl *, Type> &storedParam) {
ParamDecl *param;
Type storedType;
std::tie(param, storedType) = storedParam;
// FIXME: We are currently in process of removing `InOutType`
// so `VarDecl::get{Interface}Type` is going to wrap base
// type into `InOutType` if its flag indicates that it's
// an `inout` parameter declaration. But such type can't
// be restored directly using `VarDecl::set{Interface}Type`
// caller needs additional logic to extract base type.
if (auto *IOT = storedType->getAs<InOutType>()) {
assert(param->isInOut());
return IOT->getObjectType();
}
return storedType;
}
};
} // end anonymous namespace
/// Unless we've already done this, retypecheck the specified subexpression on
/// its own, without including any contextual constraints or parent expr
/// nodes. This is more likely to succeed than type checking the original
/// expression.
///
/// This can return a new expression (for e.g. when a UnresolvedDeclRef gets
/// resolved) and returns null when the subexpression fails to typecheck.
Expr *FailureDiagnosis::typeCheckChildIndependently(
Expr *subExpr, Type convertType, ContextualTypePurpose convertTypePurpose,
TCCOptions options, ExprTypeCheckListener *listener,
bool allowFreeTypeVariables) {
// If this sub-expression is currently being diagnosed, refuse to recheck the
// expression (which may lead to infinite recursion). If the client is
// telling us that it knows what it is doing, then believe it.
if (!options.contains(TCC_ForceRecheck)) {
if (CS.isExprBeingDiagnosed(subExpr)) {
auto *savedExpr = CS.getExprBeingDiagnosed(subExpr);
if (subExpr == savedExpr)
return subExpr;
CS.cacheExprTypes(savedExpr);
return savedExpr;
}
}
// Mark current expression as about to be diagnosed.
CS.addExprForDiagnosis(subExpr, subExpr);
// Validate contextual type before trying to use it.
std::tie(convertType, convertTypePurpose) =
validateContextualType(convertType, convertTypePurpose);
// If we have no contextual type information and the subexpr is obviously a
// overload set, don't recursively simplify this. The recursive solver will
// sometimes pick one based on arbitrary ranking behavior (e.g. like
// which is the most specialized) even then all the constraints are being
// fulfilled by UnresolvedType, which doesn't tell us anything.
if (convertTypePurpose == CTP_Unused &&
(isa<OverloadedDeclRefExpr>(subExpr->getValueProvidingExpr()))) {
return subExpr;
}
// Save any existing type data of the subexpr tree, and reset it to null in
// prep for re-type-checking the tree. If things fail, we can revert the
// types back to their original state.
ExprTypeSaverAndEraser SavedTypeData(subExpr);
// Store off the sub-expression, in case a new one is provided via the
// type check operation.
Expr *preCheckedExpr = subExpr;
// Disable structural checks, because we know that the overall expression
// has type constraint problems, and we don't want to know about any
// syntactic issues in a well-typed subexpression (which might be because
// the context is missing).
TypeCheckExprOptions TCEOptions = TypeCheckExprFlags::DisableStructuralChecks;
// Make sure that typechecker knows that this is an attempt
// to diagnose a problem.
TCEOptions |= TypeCheckExprFlags::SubExpressionDiagnostics;
// Don't walk into non-single expression closure bodies, because
// ExprTypeSaver and TypeNullifier skip them too.
TCEOptions |= TypeCheckExprFlags::SkipMultiStmtClosures;
// Claim that the result is discarded to preserve the lvalue type of
// the expression.
if (options.contains(TCC_AllowLValue))
TCEOptions |= TypeCheckExprFlags::IsDiscarded;
// If there is no contextual type available, tell typeCheckExpression that it
// is ok to produce an ambiguous result, it can just fill in holes with
// UnresolvedType and we'll deal with it.
if ((!convertType || options.contains(TCC_AllowUnresolvedTypeVariables)) &&
allowFreeTypeVariables)
TCEOptions |= TypeCheckExprFlags::AllowUnresolvedTypeVariables;
// When we're type checking a single-expression closure, we need to reset the
// DeclContext to this closure for the recursive type checking. Otherwise,
// if there is a closure in the subexpression, we can violate invariants.
auto *DC = findDeclContext(subExpr);
auto resultTy =
TypeChecker::typeCheckExpression(subExpr, DC,
TypeLoc::withoutLoc(convertType),
convertTypePurpose, TCEOptions,
listener, &CS);
CS.cacheExprTypes(subExpr);
// This is a terrible hack to get around the fact that typeCheckExpression()
// might change subExpr to point to a new OpenExistentialExpr. In that case,
// since the caller passed subExpr by value here, they would be left
// holding on to an expression containing open existential types but
// no OpenExistentialExpr, which breaks invariants enforced by the
// ASTChecker.
// Another reason why we need to do this is because diagnostics might pick
// constraint anchor for re-typechecking which would only have opaque value
// expression and not enclosing open existential, which is going to trip up
// sanitizer.
eraseOpenedExistentials(CS, subExpr);
// If recursive type checking failed, then an error was emitted. Return
// null to indicate this to the caller.
if (!resultTy)
return nullptr;
// If we type checked the result but failed to get a usable output from it,
// just pretend as though nothing happened.
if (resultTy->is<ErrorType>()) {
subExpr = preCheckedExpr;
if (subExpr->getType())
CS.cacheType(subExpr);
SavedTypeData.restore();
}
if (preCheckedExpr != subExpr)
CS.addExprForDiagnosis(preCheckedExpr, subExpr);
return subExpr;
}
DeclContext *FailureDiagnosis::findDeclContext(Expr *subExpr) const {
if (auto *closure =
dyn_cast<ClosureExpr>(subExpr->getSemanticsProvidingExpr()))
return closure->getParent();
struct DCFinder : public ASTWalker {
DeclContext *DC, *CurrDC;
Expr *SubExpr;
DCFinder(DeclContext *DC, Expr *expr) : DC(DC), CurrDC(DC), SubExpr(expr) {}
std::pair<bool, Expr *> walkToExprPre(Expr *E) override {
if (E == SubExpr) {
DC = CurrDC;
return {false, nullptr};
}
if (auto *closure = dyn_cast<ClosureExpr>(E)) {
CurrDC = closure;
// If we have a ClosureExpr parent of the specified node, check to make
// sure none of its arguments are type variables. If so, these type
// variables would be accessible to name lookup of the subexpression and
// may thus leak in. Reset them to UnresolvedTypes for safe measures.
assert(llvm::all_of(*closure->getParameters(), [](const ParamDecl *PD) {
if (PD->hasInterfaceType()) {
auto paramTy = PD->getType();
return !(paramTy->hasTypeVariable() || paramTy->hasError());
}
return true;
}));
}
return {true, E};
}
Expr *walkToExprPost(Expr *E) override {
if (auto *closure = dyn_cast<ClosureExpr>(E)) {
assert(CurrDC == closure && "DeclContext imbalance");
CurrDC = closure->getParent();
}
return E;
}
} finder(CS.DC, subExpr);
expr->walk(finder);
return finder.DC;
}
bool FailureDiagnosis::diagnoseContextualConversionError(
Expr *expr, Type contextualType, ContextualTypePurpose CTP,
Type suggestedType) {
// If the constraint system has a contextual type, then we can test to see if
// this is the problem that prevents us from solving the system.
if (!contextualType)
return false;
// Try re-type-checking the expression without the contextual type to see if
// it can work without it. If so, the contextual type is the problem. We
// force a recheck, because "expr" is likely in our table with the extra
// contextual constraint that we know we are relaxing.
TCCOptions options = TCC_ForceRecheck;
if (contextualType->is<InOutType>())
options |= TCC_AllowLValue;
auto *recheckedExpr = typeCheckChildIndependently(expr, options);
auto exprType = recheckedExpr ? CS.getType(recheckedExpr) : Type();
// If there is a suggested type and re-typecheck failed, let's use it.
if (!exprType)
exprType = suggestedType;
// If it failed and diagnosed something, then we're done.
if (!exprType)
return CS.getASTContext().Diags.hadAnyError();
// If we don't have a type for the expression, then we cannot use it in
// conversion constraint diagnostic generation. If the types match, then it
// must not be the contextual type that is the problem.
if (isUnresolvedOrTypeVarType(exprType) || exprType->isEqual(contextualType))
return false;
// Don't attempt fixits if we have an unsolved type variable, since
// the recovery path's recursion into the type checker via typeCheckCast()
// will confuse matters.
if (exprType->hasTypeVariable())
return false;
ContextualFailure failure(
CS, CTP, exprType, contextualType,
CS.getConstraintLocator(expr, LocatorPathElt::ContextualType()));
return failure.diagnoseAsError();
}
//===----------------------------------------------------------------------===//
// Diagnose assigning variable to itself.
//===----------------------------------------------------------------------===//
static bool isSymmetricBinaryOperator(const CalleeCandidateInfo &CCI) {
// If we don't have at least one known candidate, don't trigger.
if (CCI.candidates.empty()) return false;
for (auto &candidate : CCI.candidates) {
// Each candidate must be a non-assignment operator function.
auto decl = dyn_cast_or_null<FuncDecl>(candidate.getDecl());
if (!decl) return false;
auto op = dyn_cast_or_null<InfixOperatorDecl>(decl->getOperatorDecl());
if (!op || !op->getPrecedenceGroup() ||
op->getPrecedenceGroup()->isAssignment())
return false;
// It must have exactly two parameters.
auto params = decl->getParameters();
if (params->size() != 2) return false;
// Require the types to be the same.
if (!params->get(0)->getInterfaceType()->isEqual(
params->get(1)->getInterfaceType()))
return false;
}
return true;
}
/// Determine whether any of the given callee candidates have a default value.
static bool candidatesHaveAnyDefaultValues(
const CalleeCandidateInfo &candidates) {
for (const auto &cand : candidates.candidates) {
auto function = dyn_cast_or_null<AbstractFunctionDecl>(cand.getDecl());
if (!function) continue;
if (function->hasImplicitSelfDecl()) {
if (!cand.skipCurriedSelf)
return false;
} else {
if (cand.skipCurriedSelf)
return false;
}
for (auto param : *function->getParameters()) {
if (param->getDefaultArgumentKind() != DefaultArgumentKind::None)
return true;
}
}
return false;
}
/// Find the tuple element that can be initialized by a scalar.
static Optional<unsigned> getElementForScalarInitOfArg(
const TupleType *tupleTy,
const CalleeCandidateInfo &candidates) {
// Empty tuples cannot be initialized with a scalar.
if (tupleTy->getNumElements() == 0) return None;
auto getElementForScalarInitSimple =
[](const TupleType *tupleTy) -> Optional<unsigned> {
Optional<unsigned> result = None;
for (unsigned i = 0, e = tupleTy->getNumElements(); i != e; ++i) {
// If we already saw a non-vararg field, then we have more than
// one candidate field.
if (result.hasValue()) {
// Vararg fields are okay; they'll just end up being empty.
if (tupleTy->getElement(i).isVararg())
continue;
// Give up.
return None;
}
// Otherwise, remember this field number.
result = i;
}
return result;
};
// If there aren't any candidates, we're done.
if (candidates.empty()) return getElementForScalarInitSimple(tupleTy);
// Dig out the candidate.
const auto &cand = candidates[0];
auto function = dyn_cast_or_null<AbstractFunctionDecl>(cand.getDecl());
if (!function) return getElementForScalarInitSimple(tupleTy);
if (function->hasImplicitSelfDecl()) {
if (!cand.skipCurriedSelf)
return getElementForScalarInitSimple(tupleTy);
} else {
if (cand.skipCurriedSelf)
return getElementForScalarInitSimple(tupleTy);
}
auto paramList = function->getParameters();
if (tupleTy->getNumElements() != paramList->size())
return getElementForScalarInitSimple(tupleTy);
// Find a tuple element without a default.
Optional<unsigned> elementWithoutDefault;
for (unsigned i : range(tupleTy->getNumElements())) {
auto param = paramList->get(i);
// Skip parameters with default arguments.
if (param->getDefaultArgumentKind() != DefaultArgumentKind::None)
continue;
// If we already have an element without a default, check whether there are
// two fields that need initialization.
if (elementWithoutDefault) {
// Variadic fields are okay; they'll just end up being empty.
if (param->isVariadic()) continue;
// If the element we saw before was variadic, it can be empty as well.
auto priorParam = paramList->get(*elementWithoutDefault);
if (!priorParam->isVariadic()) return None;
}
elementWithoutDefault = i;
}
if (elementWithoutDefault) return elementWithoutDefault;
// All of the fields have default values; initialize the first one.
return 0;
}
/// Return true if the argument of a CallExpr (or related node) has a trailing
/// closure.
static bool callArgHasTrailingClosure(Expr *E) {
if (!E) return false;
if (auto *PE = dyn_cast<ParenExpr>(E))
return PE->hasTrailingClosure();
else if (auto *TE = dyn_cast<TupleExpr>(E))
return TE->hasTrailingClosure();
return false;
}
/// Special magic to handle inout exprs and tuples in argument lists.
Expr *FailureDiagnosis::
typeCheckArgumentChildIndependently(Expr *argExpr, Type argType,
const CalleeCandidateInfo &candidates,
TCCOptions options) {
// Grab one of the candidates (if present) and get its input list to help
// identify operators that have implicit inout arguments.
Type exampleInputType;
if (!candidates.empty()) {
exampleInputType = candidates[0].getArgumentType(CS.getASTContext());
// If we found a single candidate, and have no contextually known argument
// type information, use that one candidate as the type information for
// subexpr checking.
//
// TODO: If all candidates have the same type for some argument, we could
// pass down partial information.
if (candidates.size() == 1 && !argType)
argType = candidates[0].getArgumentType(CS.getASTContext());
}
// If our candidates are instance members at curry level #0, then the argument
// being provided is the receiver type for the instance. We produce better
// diagnostics when we don't force the self type down.
if (argType && !candidates.empty())
if (auto decl = candidates[0].getDecl())
if (decl->isInstanceMember() && !candidates[0].skipCurriedSelf &&
!isa<SubscriptDecl>(decl))
argType = Type();
// Similarly, we get better results when we don't push argument types down
// to symmetric operators.
if (argType && isSymmetricBinaryOperator(candidates))
argType = Type();
// FIXME: This should all just be a matter of getting the type of the
// sub-expression, but this doesn't work well when typeCheckChildIndependently
// is over-conservative w.r.t. TupleExprs.
auto *TE = dyn_cast<TupleExpr>(argExpr);
if (!TE) {
// If the argument isn't a tuple, it is some scalar value for a
// single-argument call.
if (exampleInputType && exampleInputType->is<InOutType>())
options |= TCC_AllowLValue;
// If the argtype is a tuple type with default arguments, or a labeled tuple
// with a single element, pull the scalar element type for the subexpression
// out. If we can't do that and the tuple has default arguments, we have to
// punt on passing down the type information, since type checking the
// subexpression won't be able to find the default argument provider.
if (argType) {
if (auto *PT = dyn_cast<ParenType>(argType.getPointer())) {
const auto &flags = PT->getParameterFlags();
if (flags.isAutoClosure()) {
auto resultTy = PT->castTo<FunctionType>()->getResult();
argType = ParenType::get(PT->getASTContext(), resultTy);
}
} else if (auto argTT = argType->getAs<TupleType>()) {
if (auto scalarElt = getElementForScalarInitOfArg(argTT, candidates)) {
// If we found the single argument being initialized, use it.
auto &arg = argTT->getElement(*scalarElt);
// If the argument being specified is actually varargs, then we're
// just specifying one element of a variadic list. Use the type of
// the individual varargs argument, not the overall array type.
if (arg.isVararg())
argType = arg.getVarargBaseTy();
else if (arg.isAutoClosure())
argType = arg.getType()->castTo<FunctionType>()->getResult();
else
argType = arg.getType();
} else if (candidatesHaveAnyDefaultValues(candidates)) {
argType = Type();
}
} else if (candidatesHaveAnyDefaultValues(candidates)) {
argType = Type();
}
}
auto CTPurpose = argType ? CTP_CallArgument : CTP_Unused;
return typeCheckChildIndependently(argExpr, argType, CTPurpose, options);
}
// If we know the requested argType to use, use computeTupleShuffle to produce
// the shuffle of input arguments to destination values. It requires a
// TupleType to compute the mapping from argExpr. Conveniently, it doesn't
// care about the actual types though, so we can just use 'void' for them.
// FIXME: This doesn't need to be limited to tuple types.
if (argType && argType->is<TupleType>()) {
// Decompose the parameter type.
SmallVector<AnyFunctionType::Param, 4> params;
AnyFunctionType::decomposeInput(argType, params);
// If we have a candidate function around, compute the position of its
// default arguments.
ParameterListInfo paramInfo;
if (!candidates.empty()) {
paramInfo = candidates[0].getParameterListInfo(params);
} else {
paramInfo = ParameterListInfo(params, nullptr, /*skipCurriedSelf=*/false);
}
// Form a set of call arguments, using a dummy type (Void), because the
// argument/parameter matching code doesn't need it.
auto voidTy = CS.getASTContext().TheEmptyTupleType;
SmallVector<AnyFunctionType::Param, 4> args;
for (unsigned i = 0, e = TE->getNumElements(); i != e; ++i) {
args.push_back(AnyFunctionType::Param(voidTy, TE->getElementName(i), {}));
}
/// Use a match call argument listener that allows relabeling.
struct RelabelMatchCallArgumentListener : MatchCallArgumentListener {
bool relabelArguments(ArrayRef<Identifier> newNames) override {
return false;
}
} listener;
SmallVector<ParamBinding, 4> paramBindings;
if (!matchCallArguments(args, params, paramInfo,
callArgHasTrailingClosure(argExpr),
/*allowFixes=*/true,
listener, paramBindings)) {
SmallVector<Expr*, 4> resultElts(TE->getNumElements(), nullptr);
SmallVector<TupleTypeElt, 4> resultEltTys(TE->getNumElements(), voidTy);
// Perform analysis of the input elements.
for (unsigned paramIdx : range(paramBindings.size())) {
// Extract the parameter.
const auto &param = params[paramIdx];
// Determine the parameter type.
if (param.isInOut())
options |= TCC_AllowLValue;
// Look at each of the arguments assigned to this parameter.
auto currentParamType = param.getOldType();
// Since this is diagnostics, let's make sure that parameter
// marked as @autoclosure indeed has a function type, because
// it can also be an error type and possibly unresolved type.
if (param.isAutoClosure()) {
if (auto *funcType = currentParamType->getAs<FunctionType>())
currentParamType = funcType->getResult();
}
for (auto inArgNo : paramBindings[paramIdx]) {
// Determine the argument type.
auto currentArgType = TE->getElement(inArgNo);
auto exprResult =
typeCheckChildIndependently(currentArgType, currentParamType,
CTP_CallArgument, options);
// If there was an error type checking this argument, then we're done.
if (!exprResult)
return nullptr;
auto resultTy = CS.getType(exprResult);
resultElts[inArgNo] = exprResult;
resultEltTys[inArgNo] = {resultTy->getInOutObjectType(),
TE->getElementName(inArgNo),
ParameterTypeFlags().withInOut(resultTy->is<InOutType>())};
}
}
auto TT = TupleType::get(resultEltTys, CS.getASTContext());
return CS.cacheType(TupleExpr::create(
CS.getASTContext(), TE->getLParenLoc(), resultElts,
TE->getElementNames(), TE->getElementNameLocs(), TE->getRParenLoc(),
TE->hasTrailingClosure(), TE->isImplicit(), TT));
}
}
// Get the simplified type of each element and rebuild the aggregate.
SmallVector<TupleTypeElt, 4> resultEltTys;
SmallVector<Expr*, 4> resultElts;
TupleType *exampleInputTuple = nullptr;
if (exampleInputType)
exampleInputTuple = exampleInputType->getAs<TupleType>();
for (unsigned i = 0, e = TE->getNumElements(); i != e; i++) {
if (exampleInputTuple && i < exampleInputTuple->getNumElements() &&
exampleInputTuple->getElement(i).isInOut())
options |= TCC_AllowLValue;
auto elExpr = typeCheckChildIndependently(TE->getElement(i), options);
if (!elExpr) return nullptr; // already diagnosed.
resultElts.push_back(elExpr);
auto resFlags =
ParameterTypeFlags().withInOut(elExpr->isSemanticallyInOutExpr());
resultEltTys.push_back({CS.getType(elExpr)->getInOutObjectType(),
TE->getElementName(i), resFlags});
}
auto TT = TupleType::get(resultEltTys, CS.getASTContext());
return CS.cacheType(TupleExpr::create(
CS.getASTContext(), TE->getLParenLoc(), resultElts, TE->getElementNames(),
TE->getElementNameLocs(), TE->getRParenLoc(), TE->hasTrailingClosure(),
TE->isImplicit(), TT));
}
static DeclName getBaseName(DeclContext *context) {
if (auto generic = context->getSelfNominalTypeDecl()) {
return generic->getName();
} else if (context->isModuleScopeContext())
return context->getParentModule()->getName();
else
llvm_unreachable("Unsupported base");
};
static void emitFixItForExplicitlyQualifiedReference(
DiagnosticEngine &de, UnresolvedDotExpr *UDE,
decltype(diag::fix_unqualified_access_top_level) diag, DeclName baseName,
DescriptiveDeclKind kind) {
auto name = baseName.getBaseIdentifier();
SmallString<32> namePlusDot = name.str();
namePlusDot.push_back('.');
de.diagnose(UDE->getLoc(), diag, namePlusDot, kind, name)
.fixItInsert(UDE->getStartLoc(), namePlusDot);
}
void ConstraintSystem::diagnoseDeprecatedConditionalConformanceOuterAccess(
UnresolvedDotExpr *UDE, ValueDecl *choice) {
auto result =
TypeChecker::lookupUnqualified(DC, UDE->getName(), UDE->getLoc());
assert(result && "names can't just disappear");
// These should all come from the same place.
auto exampleInner = result.front();
auto innerChoice = exampleInner.getValueDecl();
auto innerDC = exampleInner.getDeclContext()->getInnermostTypeContext();
auto innerParentDecl = innerDC->getSelfNominalTypeDecl();
auto innerBaseName = getBaseName(innerDC);
auto choiceKind = choice->getDescriptiveKind();
auto choiceDC = choice->getDeclContext();
auto choiceBaseName = getBaseName(choiceDC);
auto choiceParentDecl = choiceDC->getAsDecl();
auto choiceParentKind = choiceParentDecl
? choiceParentDecl->getDescriptiveKind()
: DescriptiveDeclKind::Module;
auto &DE = getASTContext().Diags;
DE.diagnose(UDE->getLoc(),
diag::warn_deprecated_conditional_conformance_outer_access,
UDE->getName(), choiceKind, choiceParentKind, choiceBaseName,
innerChoice->getDescriptiveKind(),
innerParentDecl->getDescriptiveKind(), innerBaseName);
emitFixItForExplicitlyQualifiedReference(
getASTContext().Diags, UDE,
diag::fix_deprecated_conditional_conformance_outer_access,
choiceBaseName, choiceKind);
}
static SmallVector<AnyFunctionType::Param, 4>
decomposeArgType(Type argType, ArrayRef<Identifier> argLabels) {
SmallVector<AnyFunctionType::Param, 4> result;
AnyFunctionType::decomposeInput(argType, result);
AnyFunctionType::relabelParams(result, argLabels);
return result;
}
bool FailureDiagnosis::diagnoseImplicitSelfErrors(
Expr *fnExpr, Expr *argExpr, CalleeCandidateInfo &CCI,
ArrayRef<Identifier> argLabels) {
// If candidate list is empty it means that problem is somewhere else,
// since we need to have candidates which might be shadowing other funcs.
if (CCI.empty() || !CCI[0].getDecl())
return false;
auto &ctx = CS.getASTContext();
// Call expression is formed as 'foo.bar' where 'foo' might be an
// implicit "Self" reference, such use wouldn't provide good diagnostics
// for situations where instance members have equal names to functions in
// Swift Standard Library e.g. min/max.
auto UDE = dyn_cast<UnresolvedDotExpr>(fnExpr);
if (!UDE)
return false;
auto baseExpr = dyn_cast<DeclRefExpr>(UDE->getBase());
if (!baseExpr)
return false;
auto baseDecl = baseExpr->getDecl();
if (!baseExpr->isImplicit() || baseDecl->getFullName() != ctx.Id_self)
return false;
// Our base expression is an implicit 'self.' reference e.g.
//
// extension Sequence {
// func test() -> Int {
// return max(1, 2)
// }
// }
//
// In this example the Sequence class already has two methods named 'max'
// none of which accept two arguments, but there is a function in
// Swift Standard Library called 'max' which does accept two arguments,
// so user might have called that by mistake without realizing that
// compiler would add implicit 'self.' prefix to the call of 'max'.
auto argType = CS.getType(argExpr);
// If argument wasn't properly type-checked, let's retry without changing AST.
if (!argType || argType->hasUnresolvedType() || argType->hasTypeVariable() ||
argType->hasTypeParameter()) {
auto *argTuple = dyn_cast<TupleExpr>(argExpr);
if (!argTuple) {
// Bail out if we don't have a well-formed argument list.
return false;
}
// Let's type check individual argument expressions without any
// contextual information to try to recover an argument type that
// matches what the user actually wrote instead of what the typechecker
// expects.
SmallVector<TupleTypeElt, 4> elts;
for (unsigned i = 0, e = argTuple->getNumElements(); i < e; ++i) {
ConcreteDeclRef ref = nullptr;
auto *el = argTuple->getElement(i);
auto typeResult =
TypeChecker::getTypeOfExpressionWithoutApplying(el, CS.DC, ref);
if (!typeResult)
return false;
auto flags = ParameterTypeFlags().withInOut(typeResult->is<InOutType>());
elts.push_back(TupleTypeElt(typeResult->getInOutObjectType(),
argTuple->getElementName(i),
flags));
}
argType = TupleType::get(elts, CS.getASTContext());
}
auto typeKind = argType->getKind();
if (typeKind != TypeKind::Tuple && typeKind != TypeKind::Paren)
return false;
// If argument type couldn't be properly resolved or has errors,
// we can't diagnose anything in here, it points to the different problem.
if (isUnresolvedOrTypeVarType(argType) || argType->hasError())
return false;
auto context = CS.DC;
using CandidateMap =
llvm::SmallDenseMap<ValueDecl *, llvm::SmallVector<OverloadChoice, 2>>;
auto getBaseKind = [](ValueDecl *base) -> DescriptiveDeclKind {
DescriptiveDeclKind kind = DescriptiveDeclKind::Module;
if (!base)
return kind;
auto context = base->getDeclContext();
do {
if (isa<ExtensionDecl>(context))
return DescriptiveDeclKind::Extension;
if (auto nominal = dyn_cast<NominalTypeDecl>(context)) {
kind = nominal->getDescriptiveKind();
break;
}
context = context->getParent();
} while (context);
return kind;
};
auto diagnoseShadowing = [&](ValueDecl *base,
ArrayRef<OverloadChoice> candidates) -> bool {
CalleeCandidateInfo calleeInfo(base ? base->getInterfaceType() : nullptr,
candidates, CCI.hasTrailingClosure, CS,
base);
calleeInfo.filterListArgs(decomposeArgType(argType, argLabels));
auto diagnostic = diag::member_shadows_global_function_near_match;
switch (calleeInfo.closeness) {
case CC_Unavailable:
case CC_Inaccessible:
case CC_SelfMismatch:
case CC_ArgumentLabelMismatch:
case CC_ArgumentCountMismatch:
case CC_GeneralMismatch:
return false;
case CC_NonLValueInOut:
case CC_OneArgumentNearMismatch:
case CC_OneArgumentMismatch:
case CC_OneGenericArgumentNearMismatch:
case CC_OneGenericArgumentMismatch:
case CC_ArgumentNearMismatch:
case CC_ArgumentMismatch:
case CC_GenericNonsubstitutableMismatch:
break; // Near match cases
case CC_ExactMatch:
diagnostic = diag::member_shadows_global_function;
break;
}
auto choice = calleeInfo.candidates[0].getDecl();
auto baseKind = getBaseKind(base);
auto baseName = getBaseName(choice->getDeclContext());
auto origCandidate = CCI[0].getDecl();
ctx.Diags.diagnose(UDE->getLoc(), diagnostic, UDE->getName(),
origCandidate->getDescriptiveKind(),
origCandidate->getFullName(),
choice->getDescriptiveKind(),
choice->getFullName(), baseKind, baseName);
auto topLevelDiag = diag::fix_unqualified_access_top_level;
if (baseKind == DescriptiveDeclKind::Module)
topLevelDiag = diag::fix_unqualified_access_top_level_multi;
emitFixItForExplicitlyQualifiedReference(ctx.Diags, UDE, topLevelDiag,
baseName,
choice->getDescriptiveKind());
for (auto &candidate : calleeInfo.candidates) {
if (auto decl = candidate.getDecl())
ctx.Diags.diagnose(decl, diag::decl_declared_here, decl->getFullName());
}
return true;
};
// For each of the parent contexts, let's try to find any candidates
// which have the same name and the same number of arguments as callee.
while (context->getParent()) {
auto result =
TypeChecker::lookupUnqualified(context, UDE->getName(), UDE->getLoc());
context = context->getParent();
if (!result || result.empty())
continue;
CandidateMap candidates;
for (const auto &candidate : result) {
auto base = candidate.getBaseDecl();
auto decl = candidate.getValueDecl();
if ((base && base->isInvalid()) || decl->isInvalid())
continue;
// If base is present but it doesn't represent a valid nominal,
// we can't use current candidate as one of the choices.
if (base && !base->getInterfaceType()->getNominalOrBoundGenericNominal())
continue;
auto context = decl->getDeclContext();
// We are only interested in static or global functions, because
// there is no way to call anything else properly.
if (!decl->isStatic() && !context->isModuleScopeContext())
continue;
OverloadChoice choice(base ? base->getInterfaceType() : nullptr,
decl, UDE->getFunctionRefKind());
if (base) { // Let's group all of the candidates have a common base.
candidates[base].push_back(choice);
continue;
}
// If there is no base, it means this is one of the global functions,
// let's try to diagnose its shadowing inline.
if (diagnoseShadowing(base, choice))
return true;
}
if (candidates.empty())
continue;
for (const auto &candidate : candidates) {
if (diagnoseShadowing(candidate.getFirst(), candidate.getSecond()))
return true;
}
}
return false;
}
// Extract expression for failed argument number
static Expr *getFailedArgumentExpr(CalleeCandidateInfo CCI, Expr *argExpr) {
if (auto *TE = dyn_cast<TupleExpr>(argExpr))
return TE->getElement(CCI.failedArgument.argumentNumber);
else if (auto *PE = dyn_cast<ParenExpr>(argExpr)) {
assert(CCI.failedArgument.argumentNumber == 0 &&
"Unexpected argument #");
return PE->getSubExpr();
} else {
assert(CCI.failedArgument.argumentNumber == 0 &&
"Unexpected argument #");
return argExpr;
}
}
/// If the candidate set has been narrowed down to a specific structural
/// problem, e.g. that there are too few parameters specified or that argument
/// labels don't match up, diagnose that error and return true.
bool FailureDiagnosis::diagnoseParameterErrors(CalleeCandidateInfo &CCI,
Expr *fnExpr, Expr *argExpr,
ArrayRef<Identifier> argLabels) {
if (auto *MTT = CS.getType(fnExpr)->getAs<MetatypeType>()) {
auto instTy = MTT->getInstanceType();
auto &DE = CS.getASTContext().Diags;
if (instTy->getAnyNominal()) {
// If we are invoking a constructor on a nominal type and there are
// absolutely no candidates, then they must all be private.
if (CCI.empty() || (CCI.size() == 1 && CCI.candidates[0].getDecl() &&
isa<ProtocolDecl>(CCI.candidates[0].getDecl()))) {
DE.diagnose(fnExpr->getLoc(), diag::no_accessible_initializers,
instTy);
return true;
}
// continue below
} else if (!instTy->is<TupleType>()) {
// If we are invoking a constructor on a non-nominal type, the expression
// is malformed.
SourceRange initExprRange(fnExpr->getSourceRange().Start,
argExpr->getSourceRange().End);
DE.diagnose(fnExpr->getLoc(), instTy->isExistentialType() ?
diag::construct_protocol_by_name :
diag::non_nominal_no_initializers, instTy)
.highlight(initExprRange);
return true;
}
}
// Try to diagnose errors related to the use of implicit self reference.
if (diagnoseImplicitSelfErrors(fnExpr, argExpr, CCI, argLabels))
return true;
// If we have a failure where the candidate set differs on exactly one
// argument, and where we have a consistent mismatch across the candidate set
// (often because there is only one candidate in the set), then diagnose this
// as a specific problem of passing something of the wrong type into a
// parameter.
//
// We don't generally want to use this path to diagnose calls to
// symmetrically-typed binary operators because it's likely that both
// operands contributed to the type.
if ((CCI.closeness == CC_OneArgumentMismatch ||
CCI.closeness == CC_OneArgumentNearMismatch ||
CCI.closeness == CC_OneGenericArgumentMismatch ||
CCI.closeness == CC_OneGenericArgumentNearMismatch ||
CCI.closeness == CC_GenericNonsubstitutableMismatch) &&
CCI.failedArgument.isValid() &&
!isSymmetricBinaryOperator(CCI)) {
// Map the argument number into an argument expression.
TCCOptions options = TCC_ForceRecheck;
if (CCI.failedArgument.parameterType->is<InOutType>())
options |= TCC_AllowLValue;
// It could be that the argument doesn't conform to an archetype.
Expr *badArgExpr = getFailedArgumentExpr(CCI, argExpr);
// Re-type-check the argument with the expected type of the candidate set.
// This should produce a specific and tailored diagnostic saying that the
// type mismatches with expectations.
Type paramType = CCI.failedArgument.parameterType;
if (!typeCheckChildIndependently(badArgExpr, paramType,
CTP_CallArgument, options))
return true;
}
return false;
}
bool FailureDiagnosis::diagnoseSubscriptErrors(SubscriptExpr *SE,
bool inAssignmentDestination) {
auto baseExpr = typeCheckChildIndependently(SE->getBase());
if (!baseExpr) return true;
auto baseType = CS.getType(baseExpr);
if (isa<NilLiteralExpr>(baseExpr)) {
diagnose(baseExpr->getLoc(), diag::cannot_subscript_nil_literal)
.highlight(baseExpr->getSourceRange());
return true;
}
std::function<bool(ArrayRef<OverloadChoice>)> callback =
[&](ArrayRef<OverloadChoice> candidates) -> bool {
CalleeCandidateInfo calleeInfo(Type(), candidates, SE->hasTrailingClosure(),
CS, /*selfAlreadyApplied*/ false);
// We're about to typecheck the index list, which needs to be processed with
// self already applied.
for (unsigned i = 0, e = calleeInfo.size(); i != e; ++i)
calleeInfo.candidates[i].skipCurriedSelf = true;
auto indexExpr =
typeCheckArgumentChildIndependently(SE->getIndex(), Type(), calleeInfo);
if (!indexExpr)
return true;
// Back to analyzing the candidate list with self applied.
for (unsigned i = 0, e = calleeInfo.size(); i != e; ++i)
calleeInfo.candidates[i].skipCurriedSelf = false;
ArrayRef<Identifier> argLabels = SE->getArgumentLabels();
if (diagnoseParameterErrors(calleeInfo, SE, indexExpr, argLabels))
return true;
auto indexType = CS.getType(indexExpr);
auto decomposedBaseType = decomposeArgType(baseType, {Identifier()});
auto decomposedIndexType = decomposeArgType(indexType, argLabels);
calleeInfo.filterList(
[&](OverloadCandidate cand) -> CalleeCandidateInfo::ClosenessResultTy {
// Classify how close this match is. Non-subscript decls don't match.
auto subscriptDecl = dyn_cast_or_null<SubscriptDecl>(cand.getDecl());
if (!subscriptDecl ||
(inAssignmentDestination && !subscriptDecl->supportsMutation()))
return {CC_GeneralMismatch, {}};
// Check whether the self type matches.
auto selfConstraint = CC_ExactMatch;
if (calleeInfo.evaluateCloseness(cand, decomposedBaseType).first !=
CC_ExactMatch)
selfConstraint = CC_SelfMismatch;
// Set a flag to look past the self argument to the indices.
cand.skipCurriedSelf = true;
// Explode out multi-index subscripts to find the best match.
auto indexResult =
calleeInfo.evaluateCloseness(cand, decomposedIndexType);
if (selfConstraint > indexResult.first)
return {selfConstraint, {}};
return indexResult;
});
// If the closest matches all mismatch on self, we either have something
// that cannot be subscripted, or an ambiguity.
if (calleeInfo.closeness == CC_SelfMismatch) {
diagnose(SE->getLoc(), diag::cannot_subscript_base, baseType)
.highlight(SE->getBase()->getSourceRange());
// FIXME: Should suggest overload set, but we're not ready for that until
// it points to candidates and identifies the self type in the diagnostic.
// calleeInfo.suggestPotentialOverloads(SE->getLoc());
return true;
}
// Any other failures relate to the index list.
for (unsigned i = 0, e = calleeInfo.size(); i != e; ++i)
calleeInfo.candidates[i].skipCurriedSelf = true;
// TODO: Is there any reason to check for CC_NonLValueInOut here?
if (calleeInfo.closeness == CC_ExactMatch) {
auto message = diag::ambiguous_subscript;
// If there is an exact match on the argument with
// a single candidate, let's type-check subscript
// as a whole to figure out if there is any structural
// problem after all.
if (calleeInfo.size() == 1) {
Expr *expr = SE;
ConcreteDeclRef decl = nullptr;
message = diag::cannot_subscript_with_index;
if (TypeChecker::getTypeOfExpressionWithoutApplying(expr, CS.DC, decl))
return false;
// If we are down to a single candidate but with an unresolved
// index type, we can substitute in the base type to get a simpler
// and more concrete expected type for this subscript decl, in order
// to diagnose a better error.
if (baseType && indexType->hasUnresolvedType()) {
auto cand = calleeInfo.candidates[0];
auto candType = baseType->getTypeOfMember(CS.DC->getParentModule(),
cand.getDecl(), nullptr);
if (auto *candFunc = candType->getAs<FunctionType>()) {
auto paramsType = FunctionType::composeInput(CS.getASTContext(),
candFunc->getParams(),
false);
if (!typeCheckChildIndependently(
indexExpr, paramsType, CTP_CallArgument, TCC_ForceRecheck))
return true;
}
}
}
diagnose(SE->getLoc(), message, baseType, indexType)
.highlight(indexExpr->getSourceRange())
.highlight(baseExpr->getSourceRange());
// FIXME: suggestPotentialOverloads should do this.
// calleeInfo.suggestPotentialOverloads(SE->getLoc());
for (auto candidate : calleeInfo.candidates)
if (auto decl = candidate.getDecl())
diagnose(decl, diag::found_candidate);
else
diagnose(candidate.getExpr()->getLoc(), diag::found_candidate);
return true;
}
if (diagnoseParameterErrors(calleeInfo, SE, indexExpr, argLabels))
return true;
// Diagnose some simple and common errors.
if (calleeInfo.diagnoseSimpleErrors(SE))
return true;
diagnose(SE->getLoc(), diag::cannot_subscript_with_index, baseType,
indexType);
calleeInfo.suggestPotentialOverloads(SE->getLoc());
return true;
};
auto locator =
CS.getConstraintLocator(SE, ConstraintLocator::SubscriptMember);
return diagnoseMemberFailures(SE, baseExpr, ConstraintKind::ValueMember,
DeclNameRef::createSubscript(),
FunctionRefKind::DoubleApply, locator,
callback);
}
bool FailureDiagnosis::visitSubscriptExpr(SubscriptExpr *SE) {
return diagnoseSubscriptErrors(SE, /* inAssignmentDestination = */ false);
}
namespace {
/// Type checking listener for pattern binding initializers.
class CalleeListener : public ExprTypeCheckListener {
Type contextualType;
public:
explicit CalleeListener(Type contextualType)
: contextualType(contextualType) { }
bool builtConstraints(ConstraintSystem &cs, Expr *expr) override {
// If we have no contextual type, there is nothing to do.
if (!contextualType)
return false;
// If the expression is obviously something that produces a metatype,
// then don't put a constraint on it.
auto semExpr = expr->getValueProvidingExpr();
if (isa<TypeExpr>(semExpr))
return false;
auto resultLocator =
cs.getConstraintLocator(expr, ConstraintLocator::FunctionResult);
auto resultType = cs.createTypeVariable(resultLocator,
TVO_CanBindToLValue |
TVO_CanBindToNoEscape);
auto locator = cs.getConstraintLocator(expr);
cs.addConstraint(ConstraintKind::FunctionResult,
cs.getType(expr),
resultType,
locator);
cs.addConstraint(ConstraintKind::Conversion,
resultType,
contextualType,
locator);
return false;
}
};
} // end anonymous namespace
// Check if there is a structural problem in the function expression
// by performing type checking with the option to allow unresolved
// type variables. If that is going to produce a function type with
// unresolved result let's not re-typecheck the function expression,
// because it might produce unrelated diagnostics due to lack of
// contextual information.
static bool shouldTypeCheckFunctionExpr(FailureDiagnosis &FD, DeclContext *DC,
Expr *fnExpr) {
if (!isa<UnresolvedDotExpr>(fnExpr))
return true;
SmallPtrSet<TypeBase *, 4> fnTypes;
FD.getPossibleTypesOfExpressionWithoutApplying(
fnExpr, DC, fnTypes, FreeTypeVariableBinding::UnresolvedType);
if (fnTypes.size() == 1) {
// Some member types depend on the arguments to produce a result type,
// type-checking such expressions without associated arguments is
// going to produce unrelated diagnostics.
if (auto fn = (*fnTypes.begin())->getAs<AnyFunctionType>()) {
auto resultType = fn->getResult();
if (resultType->hasUnresolvedType() || resultType->hasTypeVariable())
return false;
}
}
// Might be a structural problem related to the member itself.
return true;
}
bool FailureDiagnosis::visitApplyExpr(ApplyExpr *callExpr) {
auto *fnExpr = callExpr->getFn();
if (shouldTypeCheckFunctionExpr(*this, CS.DC, fnExpr)) {
// Type check the function subexpression to resolve a type for it if
// possible.
fnExpr = typeCheckChildIndependently(callExpr->getFn());
if (!fnExpr) {
return CS.getASTContext().Diags.hadAnyError();
}
}
SWIFT_DEFER {
if (!fnExpr) return;
// If it's a member operator reference, put the operator back.
if (auto operatorRef = fnExpr->getMemberOperatorRef())
callExpr->setFn(operatorRef);
};
auto getFuncType = [](Type type) -> Type { return type->getRValueType(); };
auto fnType = getFuncType(CS.getType(fnExpr));
bool hasTrailingClosure = callArgHasTrailingClosure(callExpr->getArg());
// Collect a full candidate list of callees based on the partially type
// checked function.
CalleeCandidateInfo calleeInfo(fnExpr, hasTrailingClosure, CS);
// Filter list of the candidates based on the known function type.
if (auto fn = fnType->getAs<AnyFunctionType>()) {
using Closeness = CalleeCandidateInfo::ClosenessResultTy;
calleeInfo.filterList([&](OverloadCandidate candidate) -> Closeness {
auto resultType = candidate.getResultType();
if (!resultType)
return {CC_GeneralMismatch, {}};
// FIXME: Handle matching of the generic types properly.
// Currently we don't filter result types containing generic parameters
// because there is no easy way to do that, and candidate set is going
// to be pruned by matching of the argument types later on anyway, so
// it's better to over report than to be too conservative.
if (resultType->isEqual(fn->getResult()))
return {CC_ExactMatch, {}};
return {CC_GeneralMismatch, {}};
});
}
// Filter the candidate list based on the argument we may or may not have.
calleeInfo.filterContextualMemberList(callExpr->getArg());
SmallVector<Identifier, 2> argLabelsScratch;
ArrayRef<Identifier> argLabels =
callExpr->getArgumentLabels(argLabelsScratch);
if (diagnoseParameterErrors(calleeInfo, callExpr->getFn(),
callExpr->getArg(), argLabels))
return true;
Type argType; // argument list, if known.
if (auto FTy = fnType->getAs<AnyFunctionType>()) {
argType = FunctionType::composeInput(CS.getASTContext(), FTy->getParams(),
false);
} else if (auto MTT = fnType->getAs<AnyMetatypeType>()) {
// If we are constructing a tuple with initializer syntax, the expected
// argument list is the tuple type itself - and there is no initdecl.
auto instanceTy = MTT->getInstanceType();
if (auto tupleTy = instanceTy->getAs<TupleType>()) {
argType = tupleTy;
}
}
// Let's check whether this is a situation when callee expects
// no arguments but N are given. Otherwise, just below
// `typeCheckArgumentChild*` is going to use `()` is a contextual type which
// is incorrect.
if (argType && argType->isVoid()) {
auto *argExpr = callExpr->getArg();
if (isa<ParenExpr>(argExpr) ||
(isa<TupleExpr>(argExpr) &&
cast<TupleExpr>(argExpr)->getNumElements() > 0)) {
diagnose(callExpr->getLoc(), diag::extra_argument_to_nullary_call)
.highlight(argExpr->getSourceRange());
return true;
}
}
// Get the expression result of type checking the arguments to the call
// independently, so we have some idea of what we're working with.
//
auto argExpr = typeCheckArgumentChildIndependently(callExpr->getArg(),
argType, calleeInfo,
TCC_AllowUnresolvedTypeVariables);
if (!argExpr)
return true; // already diagnosed.
calleeInfo.filterListArgs(decomposeArgType(CS.getType(argExpr), argLabels));
if (diagnoseParameterErrors(calleeInfo, callExpr->getFn(), argExpr,
argLabels))
return true;
// Diagnose some simple and common errors.
if (calleeInfo.diagnoseSimpleErrors(callExpr))
return true;
// Force recheck of the arg expression because we allowed unresolved types
// before, and that turned out not to help, and now we want any diagnoses
// from disallowing them.
argExpr = typeCheckArgumentChildIndependently(callExpr->getArg(), argType,
calleeInfo, TCC_ForceRecheck);
if (!argExpr)
return true; // already diagnosed.
// Handle argument label mismatches when we have multiple candidates.
if (calleeInfo.closeness == CC_ArgumentLabelMismatch) {
auto args = decomposeArgType(CS.getType(argExpr), argLabels);
// If we have multiple candidates that we fail to match, just say we have
// the wrong labels and list the candidates out.
diagnose(callExpr->getLoc(), diag::wrong_argument_labels_overload,
getParamListAsString(args))
.highlight(argExpr->getSourceRange());
// Did the user intend on invoking a different overload?
calleeInfo.suggestPotentialOverloads(fnExpr->getLoc());
return true;
}
auto overloadName = calleeInfo.declName;
// Local function to check if the error with argument type is
// related to contextual type information of the enclosing expression
// rather than resolution of argument expression itself.
auto isContextualConversionFailure = [&](Expr *argExpr) -> bool {
// If we found an exact match, this must be a problem with a conversion from
// the result of the call to the expected type. Diagnose this as a
// conversion failure.
if (calleeInfo.closeness == CC_ExactMatch)
return true;
if (!CS.getContextualType() ||
(calleeInfo.closeness != CC_ArgumentMismatch &&
calleeInfo.closeness != CC_OneGenericArgumentMismatch))
return false;
CalleeCandidateInfo candidates(fnExpr, hasTrailingClosure, CS);
// Filter original list of choices based on the deduced type of
// argument expression after force re-check.
candidates.filterContextualMemberList(argExpr);
// One of the candidates matches exactly, which means that
// this is a contextual type conversion failure, we can't diagnose here.
return candidates.closeness == CC_ExactMatch;
};
// Otherwise, we have a generic failure. Diagnose it with a generic error
// message now.
if (isa<BinaryExpr>(callExpr) && isa<TupleExpr>(argExpr)) {
auto argTuple = cast<TupleExpr>(argExpr);
auto lhsExpr = argTuple->getElement(0), rhsExpr = argTuple->getElement(1);
auto lhsType = CS.getType(lhsExpr)->getRValueType();
auto rhsType = CS.getType(rhsExpr)->getRValueType();
// TODO(diagnostics): There are still cases not yet handled by new
// diagnostics framework e.g.
//
// var tuple = (1, 2, 3)
// switch tuple {
// case (let (_, _, _)) + 1: break
// }
if (callExpr->isImplicit() && overloadName == "~=") {
auto flags = ParameterTypeFlags();
if (calleeInfo.candidates.size() == 1)
if (auto fnType = calleeInfo.candidates[0].getFunctionType())
flags = fnType->getParams()[0].getParameterFlags();
auto *locator = CS.getConstraintLocator(
callExpr,
{ConstraintLocator::ApplyArgument,
LocatorPathElt::ApplyArgToParam(0, 0, flags)},
/*summaryFlags=*/0);
ArgumentMismatchFailure failure(CS, lhsType, rhsType, locator);
return failure.diagnosePatternMatchingMismatch();
}
if (isContextualConversionFailure(argTuple))
return false;
if (!lhsType->isEqual(rhsType)) {
auto diag = diagnose(callExpr->getLoc(), diag::cannot_apply_binop_to_args,
overloadName, lhsType, rhsType);
diag.highlight(lhsExpr->getSourceRange())
.highlight(rhsExpr->getSourceRange());
} else {
diagnose(callExpr->getLoc(), diag::cannot_apply_binop_to_same_args,
overloadName, lhsType)
.highlight(lhsExpr->getSourceRange())
.highlight(rhsExpr->getSourceRange());
}
calleeInfo.suggestPotentialOverloads(callExpr->getLoc());
return true;
}
// If we have a failure where closeness is an exact match, but there is
// still a failed argument, it is because one (or more) of the arguments
// types are unresolved.
if (calleeInfo.closeness == CC_ExactMatch && calleeInfo.failedArgument.isValid()) {
diagnoseAmbiguity(getFailedArgumentExpr(calleeInfo, argExpr));
return true;
}
if (isContextualConversionFailure(argExpr))
return false;
// Generate specific error messages for unary operators.
if (isa<PrefixUnaryExpr>(callExpr) || isa<PostfixUnaryExpr>(callExpr)) {
assert(!overloadName.empty());
diagnose(argExpr->getLoc(), diag::cannot_apply_unop_to_arg, overloadName,
CS.getType(argExpr));
calleeInfo.suggestPotentialOverloads(argExpr->getLoc());
return true;
}
if (CS.getType(argExpr)->hasUnresolvedType())
return false;
SmallVector<AnyFunctionType::Param, 8> params;
AnyFunctionType::decomposeInput(CS.getType(argExpr), params);
auto argString = AnyFunctionType::getParamListAsString(params);
// If we couldn't get the name of the callee, then it must be something of a
// more complex "value of function type".
if (overloadName.empty()) {
// If we couldn't infer the result type of the closure expr, then we have
// some sort of ambiguity, let the ambiguity diagnostic stuff handle this.
if (auto ffty = fnType->getAs<AnyFunctionType>())
if (ffty->getResult()->hasTypeVariable()) {
diagnoseAmbiguity(fnExpr);
return true;
}
// The most common unnamed value of closure type is a ClosureExpr, so
// special case it.
if (isa<ClosureExpr>(fnExpr->getValueProvidingExpr())) {
if (fnType->hasTypeVariable())
diagnose(argExpr->getStartLoc(), diag::cannot_invoke_closure, argString)
.highlight(fnExpr->getSourceRange());
else
diagnose(argExpr->getStartLoc(), diag::cannot_invoke_closure_type,
fnType, argString)
.highlight(fnExpr->getSourceRange());
} else if (fnType->hasTypeVariable()) {
diagnose(argExpr->getStartLoc(), diag::cannot_call_function_value,
argString)
.highlight(fnExpr->getSourceRange());
} else {
diagnose(argExpr->getStartLoc(), diag::cannot_call_value_of_function_type,
fnType, argString)
.highlight(fnExpr->getSourceRange());
}
return true;
}
if (auto MTT = fnType->getAs<MetatypeType>()) {
if (MTT->getInstanceType()->isExistentialType()) {
diagnose(fnExpr->getLoc(), diag::construct_protocol_value, fnType);
return true;
}
}
bool isInitializer = isa<TypeExpr>(fnExpr);
if (isa<TupleExpr>(argExpr) &&
cast<TupleExpr>(argExpr)->getNumElements() == 0) {
// Emit diagnostics that say "no arguments".
diagnose(fnExpr->getLoc(), diag::cannot_call_with_no_params,
overloadName, isInitializer);
} else {
diagnose(fnExpr->getLoc(), diag::cannot_call_with_params,
overloadName, argString, isInitializer);
}
// Did the user intend on invoking a different overload?
calleeInfo.suggestPotentialOverloads(fnExpr->getLoc());
return true;
}
bool FailureDiagnosis::visitCoerceExpr(CoerceExpr *CE) {
// Coerce the input to whatever type is specified by the CoerceExpr.
auto expr = typeCheckChildIndependently(CE->getSubExpr(),
CS.getType(CE->getCastTypeLoc()),
CTP_CoerceOperand);
if (!expr)
return true;
auto ref = expr->getReferencedDecl();
if (auto *decl = ref.getDecl()) {
// Without explicit coercion we might end up
// type-checking sub-expression as unavaible
// declaration, let's try to diagnose that here.
if (AvailableAttr::isUnavailable(decl))
return diagnoseExplicitUnavailability(
decl, expr->getSourceRange(), CS.DC, dyn_cast<ApplyExpr>(expr));
}
return false;
}
bool FailureDiagnosis::visitIfExpr(IfExpr *IE) {
auto typeCheckClauseExpr = [&](Expr *clause, Type contextType = Type(),
ContextualTypePurpose convertPurpose =
CTP_Unused) -> Expr * {
// Provide proper contextual type when type conversion is specified.
return typeCheckChildIndependently(clause, contextType, convertPurpose,
TCCOptions(), nullptr, false);
};
// Check all of the subexpressions independently.
auto condExpr = typeCheckClauseExpr(IE->getCondExpr());
if (!condExpr) return true;
auto trueExpr = typeCheckClauseExpr(IE->getThenExpr(), CS.getContextualType(),
CS.getContextualTypePurpose());
if (!trueExpr) return true;
auto falseExpr = typeCheckClauseExpr(
IE->getElseExpr(), CS.getContextualType(), CS.getContextualTypePurpose());
if (!falseExpr) return true;
// If the true/false values already match, it must be a contextual problem.
if (CS.getType(trueExpr)->isEqual(CS.getType(falseExpr)))
return false;
// Otherwise, the true/false result types must not be matching.
diagnose(IE->getColonLoc(), diag::if_expr_cases_mismatch,
CS.getType(trueExpr), CS.getType(falseExpr))
.highlight(trueExpr->getSourceRange())
.highlight(falseExpr->getSourceRange());
return true;
}
bool FailureDiagnosis::
visitRebindSelfInConstructorExpr(RebindSelfInConstructorExpr *E) {
// Don't walk the children for this node, it leads to multiple diagnostics
// because of how sema injects this node into the type checker.
return false;
}
bool FailureDiagnosis::visitArrayExpr(ArrayExpr *E) {
// If we had a contextual type, then it either conforms to
// ExpressibleByArrayLiteral or it is an invalid contextual type.
auto contextualType = CS.getContextualType();
if (!contextualType) {
return false;
}
// If our contextual type is an optional, look through them, because we're
// surely initializing whatever is inside.
contextualType = contextualType->lookThroughAllOptionalTypes();
// Validate that the contextual type conforms to ExpressibleByArrayLiteral and
// figure out what the contextual element type is in place.
auto ALC =
TypeChecker::getProtocol(CS.getASTContext(), E->getLoc(),
KnownProtocolKind::ExpressibleByArrayLiteral);
if (!ALC)
return visitExpr(E);
// Check to see if the contextual type conforms.
auto Conformance = TypeChecker::conformsToProtocol(
contextualType, ALC, CS.DC, ConformanceCheckFlags::InExpression);
if (Conformance) {
Type contextualElementType =
Conformance
.getTypeWitnessByName(contextualType,
CS.getASTContext().Id_ArrayLiteralElement)
->getDesugaredType();
// Type check each of the subexpressions in place, passing down the contextual
// type information if we have it.
for (auto elt : E->getElements()) {
if (typeCheckChildIndependently(elt, contextualElementType,
CTP_ArrayElement) == nullptr) {
return true;
}
}
return false;
}
ContextualFailure failure(CS, CS.getType(E), contextualType,
CS.getConstraintLocator(E));
if (failure.diagnoseConversionToDictionary())
return true;
// If that didn't turn up an issue, then we don't know what to do.
// TODO: When a contextual type is missing, we could try to diagnose cases
// where the element types mismatch... but theoretically they should type
// unify to Any, so that could never happen?
return false;
}
bool FailureDiagnosis::visitDictionaryExpr(DictionaryExpr *E) {
Type contextualKeyType, contextualValueType;
auto keyTypePurpose = CTP_Unused, valueTypePurpose = CTP_Unused;
// If we had a contextual type, then it either conforms to
// ExpressibleByDictionaryLiteral or it is an invalid contextual type.
if (auto contextualType = CS.getContextualType()) {
// If our contextual type is an optional, look through them, because we're
// surely initializing whatever is inside.
contextualType = contextualType->lookThroughAllOptionalTypes();
auto DLC = TypeChecker::getProtocol(
CS.getASTContext(), E->getLoc(),
KnownProtocolKind::ExpressibleByDictionaryLiteral);
if (!DLC) return visitExpr(E);
// Validate the contextual type conforms to ExpressibleByDictionaryLiteral
// and figure out what the contextual Key/Value types are in place.
auto Conformance = TypeChecker::conformsToProtocol(
contextualType, DLC, CS.DC, ConformanceCheckFlags::InExpression);
if (Conformance.isInvalid()) {
diagnose(E->getStartLoc(), diag::type_is_not_dictionary, contextualType)
.highlight(E->getSourceRange());
return true;
}
contextualKeyType =
Conformance
.getTypeWitnessByName(contextualType, CS.getASTContext().Id_Key)
->getDesugaredType();
contextualValueType =
Conformance
.getTypeWitnessByName(contextualType, CS.getASTContext().Id_Value)
->getDesugaredType();
assert(contextualKeyType && contextualValueType &&
"Could not find Key/Value DictionaryLiteral associated types from"
" contextual type conformance");
keyTypePurpose = CTP_DictionaryKey;
valueTypePurpose = CTP_DictionaryValue;
}
// Type check each of the subexpressions in place, passing down the contextual
// type information if we have it.
for (auto elt : E->getElements()) {
auto TE = dyn_cast<TupleExpr>(elt);
if (!TE || TE->getNumElements() != 2) continue;
if (!typeCheckChildIndependently(TE->getElement(0),
contextualKeyType, keyTypePurpose))
return true;
if (!typeCheckChildIndependently(TE->getElement(1),
contextualValueType, valueTypePurpose))
return true;
}
// If that didn't turn up an issue, then we don't know what to do.
// TODO: When a contextual type is missing, we could try to diagnose cases
// where the element types mismatch. There is no Any equivalent since they
// keys need to be hashable.
return false;
}
/// When an object literal fails to typecheck because its protocol's
/// corresponding default type has not been set in the global namespace (e.g.
/// _ColorLiteralType), suggest that the user import the appropriate module for
/// the target.
bool FailureDiagnosis::visitObjectLiteralExpr(ObjectLiteralExpr *E) {
// Type check the argument first.
auto protocol = TypeChecker::getLiteralProtocol(CS.getASTContext(), E);
if (!protocol)
return false;
auto constrName =
TypeChecker::getObjectLiteralConstructorName(CS.getASTContext(), E);
assert(constrName);
auto *constr = dyn_cast_or_null<ConstructorDecl>(
protocol->getSingleRequirement(constrName));
if (!constr)
return false;
auto paramType = TypeChecker::getObjectLiteralParameterType(E, constr);
if (!typeCheckChildIndependently(
E->getArg(), paramType, CTP_CallArgument))
return true;
// Conditions for showing this diagnostic:
// * The object literal protocol's default type is unimplemented
if (TypeChecker::getDefaultType(protocol, CS.DC))
return false;
// * The object literal has no contextual type
if (CS.getContextualType())
return false;
// Figure out what import to suggest.
auto &Ctx = CS.getASTContext();
const auto &target = Ctx.LangOpts.Target;
StringRef importModule;
StringRef importDefaultTypeName;
if (protocol == Ctx.getProtocol(KnownProtocolKind::ExpressibleByColorLiteral)) {
if (target.isMacOSX()) {
importModule = "AppKit";
importDefaultTypeName = "NSColor";
} else if (target.isiOS() || target.isTvOS()) {
importModule = "UIKit";
importDefaultTypeName = "UIColor";
}
} else if (protocol == Ctx.getProtocol(
KnownProtocolKind::ExpressibleByImageLiteral)) {
if (target.isMacOSX()) {
importModule = "AppKit";
importDefaultTypeName = "NSImage";
} else if (target.isiOS() || target.isTvOS()) {
importModule = "UIKit";
importDefaultTypeName = "UIImage";
}
} else if (protocol == Ctx.getProtocol(
KnownProtocolKind::ExpressibleByFileReferenceLiteral)) {
importModule = "Foundation";
importDefaultTypeName = "URL";
}
// Emit the diagnostic.
const auto plainName = E->getLiteralKindPlainName();
Ctx.Diags.diagnose(E->getLoc(), diag::object_literal_default_type_missing,
plainName);
if (!importModule.empty()) {
Ctx.Diags.diagnose(E->getLoc(), diag::object_literal_resolve_import,
importModule, importDefaultTypeName, plainName);
}
return true;
}
bool FailureDiagnosis::visitUnresolvedMemberExpr(UnresolvedMemberExpr *E) {
// If we have no contextual type, there is no way to resolve this. Just
// diagnose this as an ambiguity.
if (!CS.getContextualType())
return false;
// OTOH, if we do have a contextual type, we can provide a more specific
// error. Dig out the UnresolvedValueMember constraint for this expr node.
Constraint *memberConstraint = nullptr;
auto checkConstraint = [&](Constraint *C) {
if (C->getKind() == ConstraintKind::UnresolvedValueMember &&
simplifyLocatorToAnchor(C->getLocator()) == E)
memberConstraint = C;
};
if (CS.failedConstraint)
checkConstraint(CS.failedConstraint);
for (auto &C : CS.getConstraints()) {
if (memberConstraint) break;
checkConstraint(&C);
}
// If we can't find the member constraint in question, then we failed.
if (!memberConstraint)
return false;
std::function<bool(ArrayRef<OverloadChoice>)> callback = [&](
ArrayRef<OverloadChoice> candidates) {
bool hasTrailingClosure = callArgHasTrailingClosure(E->getArgument());
// Dump all of our viable candidates into a CalleeCandidateInfo & sort it
// out.
CalleeCandidateInfo candidateInfo(Type(), candidates, hasTrailingClosure,
CS);
// Filter the candidate list based on the argument we may or may not have.
candidateInfo.filterContextualMemberList(E->getArgument());
// If we have multiple candidates, then we have an ambiguity.
if (candidateInfo.size() != 1) {
SourceRange argRange;
if (auto arg = E->getArgument())
argRange = arg->getSourceRange();
diagnose(E->getNameLoc(), diag::ambiguous_member_overload_set,
E->getName())
.highlight(argRange);
candidateInfo.suggestPotentialOverloads(E->getNameLoc().getBaseNameLoc());
return true;
}
return false;
};
return diagnoseMemberFailures(E, nullptr, memberConstraint->getKind(),
memberConstraint->getMember(),
memberConstraint->getFunctionRefKind(),
memberConstraint->getLocator(), callback);
}
bool FailureDiagnosis::diagnoseMemberFailures(
Expr *E, Expr *baseExpr, ConstraintKind lookupKind, DeclNameRef memberName,
FunctionRefKind funcRefKind, ConstraintLocator *locator,
Optional<std::function<bool(ArrayRef<OverloadChoice>)>> callback,
bool includeInaccessibleMembers) {
auto isInitializer = memberName.isSimpleName(DeclBaseName::createConstructor());
// Get the referenced base expression from the failed constraint, along with
// the SourceRange for the member ref. In "x.y", this returns the expr for x
// and the source range for y.
SourceRange memberRange;
SourceLoc BaseLoc;
DeclNameLoc NameLoc;
Type baseTy, baseObjTy;
// UnresolvedMemberExpr doesn't have "base" expression,
// it's represented as ".foo", which means that we need
// to get base from the context.
if (auto *UME = dyn_cast<UnresolvedMemberExpr>(E)) {
memberRange = E->getSourceRange();
BaseLoc = E->getLoc();
NameLoc = UME->getNameLoc();
baseTy = CS.getContextualType();
if (!baseTy)
return false;
// If we succeeded, get ready to do the member lookup.
baseObjTy = baseTy->getRValueType();
// If the base object is already a metatype type, then something weird is
// going on. For now, just generate a generic error.
if (baseObjTy->is<MetatypeType>())
return false;
baseTy = baseObjTy = MetatypeType::get(baseObjTy);
} else {
memberRange = baseExpr->getSourceRange();
if (locator)
locator = simplifyLocator(CS, locator, memberRange);
BaseLoc = baseExpr->getLoc();
NameLoc = DeclNameLoc(memberRange.Start);
// Retypecheck the anchor type, which is the base of the member expression.
baseExpr = typeCheckChildIndependently(baseExpr, TCC_AllowLValue);
if (!baseExpr)
return true;
baseTy = CS.getType(baseExpr);
baseObjTy = baseTy->getWithoutSpecifierType();
}
// If the base type is an IUO, look through it. Odds are, the code is not
// trying to find a member of it.
// FIXME: We need to rework this with IUOs out of the type system.
// if (auto objTy = CS.lookThroughImplicitlyUnwrappedOptionalType(baseObjTy))
// baseTy = baseObjTy = objTy;
// If the base of this property access is a function that takes an empty
// argument list, then the most likely problem is that the user wanted to
// call the function, e.g. in "a.b.c" where they had to write "a.b().c".
// Produce a specific diagnostic + fixit for this situation.
if (auto baseFTy = baseObjTy->getAs<AnyFunctionType>()) {
if (baseExpr && baseFTy->getParams().empty()) {
auto failure =
MissingCallFailure(CS, CS.getConstraintLocator(baseExpr));
return failure.diagnoseAsError();
}
}
// If this is a tuple, then the index needs to be valid.
if (auto tuple = baseObjTy->getAs<TupleType>()) {
auto baseName = memberName.getBaseName();
if (!baseName.isSpecial()) {
StringRef nameStr = baseName.userFacingName();
int fieldIdx = -1;
// Resolve a number reference into the tuple type.
unsigned Value = 0;
if (!nameStr.getAsInteger(10, Value) && Value < tuple->getNumElements()) {
fieldIdx = Value;
} else {
fieldIdx = tuple->getNamedElementId(memberName.getBaseIdentifier());
}
if (fieldIdx != -1)
return false; // Lookup is valid.
}
diagnose(BaseLoc, diag::could_not_find_tuple_member, baseObjTy, memberName)
.highlight(memberRange);
return true;
}
// If this is initializer/constructor lookup we are dealing this.
if (isInitializer) {
// Let's check what is the base type we are trying to look it up on
// because only MetatypeType is viable to find constructor on, as per
// rules in ConstraintSystem::performMemberLookup.
if (!baseTy->is<AnyMetatypeType>()) {
baseTy = MetatypeType::get(baseTy, CS.getASTContext());
}
}
// If base type has unresolved generic parameters, such might mean
// that it's initializer with erroneous argument, otherwise this would
// be a simple ambiguous archetype case, neither can be diagnosed here.
if (baseTy->hasTypeParameter() && baseTy->hasUnresolvedType())
return false;
MemberLookupResult result =
CS.performMemberLookup(lookupKind, memberName, baseTy, funcRefKind,
locator, includeInaccessibleMembers);
switch (result.OverallResult) {
case MemberLookupResult::Unsolved:
// If we couldn't resolve a specific type for the base expression, then we
// cannot produce a specific diagnostic.
return false;
case MemberLookupResult::ErrorAlreadyDiagnosed:
// If an error was already emitted, then we're done, don't emit anything
// redundant.
return true;
case MemberLookupResult::HasResults:
break;
}
SmallVector<OverloadChoice, 4> viableCandidatesToReport;
for (auto candidate : result.ViableCandidates)
if (candidate.getKind() != OverloadChoiceKind::KeyPathApplication)
viableCandidatesToReport.push_back(candidate);
// Since the lookup was allowing inaccessible members, let's check
// if it found anything of that sort, which is easy to diagnose.
bool allUnavailable =
!CS.getASTContext().LangOpts.DisableAvailabilityChecking;
bool allInaccessible = true;
for (auto &member : viableCandidatesToReport) {
if (!member.isDecl()) {
// if there is no declaration, this choice is implicitly available.
allUnavailable = false;
continue;
}
auto decl = member.getDecl();
// Check availability of the found choice.
if (!decl->getAttrs().isUnavailable(CS.getASTContext()))
allUnavailable = false;
if (decl->isAccessibleFrom(CS.DC))
allInaccessible = false;
}
// diagnoseSimpleErrors() should have diagnosed this scenario.
assert(!allInaccessible || viableCandidatesToReport.empty());
if (result.UnviableCandidates.empty() && isInitializer &&
!baseObjTy->is<AnyMetatypeType>()) {
if (auto ctorRef = dyn_cast<UnresolvedDotExpr>(E)) {
// Diagnose 'super.init', which can only appear inside another
// initializer, specially.
if (isa<SuperRefExpr>(ctorRef->getBase())) {
diagnose(BaseLoc, diag::super_initializer_not_in_initializer);
return true;
}
// Suggest inserting a call to 'type(of:)' to construct another object
// of the same dynamic type.
SourceRange fixItRng = ctorRef->getNameLoc().getSourceRange();
// Surround the caller in `type(of:)`.
diagnose(BaseLoc, diag::init_not_instance_member)
.fixItInsert(fixItRng.Start, "type(of: ")
.fixItInsertAfter(fixItRng.End, ")");
return true;
}
}
if (viableCandidatesToReport.empty()) {
// If this was an optional type let's check if the base type
// has requested member, if so - generate nice error saying that
// optional was not unwrapped, otherwise say that type value has
// no such member.
if (auto *OT = dyn_cast<OptionalType>(baseObjTy.getPointer())) {
auto optionalResult = CS.performMemberLookup(
lookupKind, memberName, OT->getBaseType(), funcRefKind, locator,
/*includeInaccessibleMembers*/ false);
switch (optionalResult.OverallResult) {
case MemberLookupResult::ErrorAlreadyDiagnosed:
// If an error was already emitted, then we're done, don't emit anything
// redundant.
return true;
case MemberLookupResult::Unsolved:
case MemberLookupResult::HasResults:
break;
}
if (!optionalResult.ViableCandidates.empty()) {
MemberAccessOnOptionalBaseFailure failure(
CS, CS.getConstraintLocator(baseExpr), memberName,
/*resultOptional=*/false);
return failure.diagnoseAsError();
}
}
// FIXME: Dig out the property DeclNameLoc.
diagnoseUnviableLookupResults(result, E, baseObjTy, baseExpr, memberName,
NameLoc, BaseLoc);
return true;
}
if (allUnavailable) {
auto firstDecl = viableCandidatesToReport[0].getDecl();
// FIXME: We need the enclosing CallExpr to rewrite the argument labels.
if (diagnoseExplicitUnavailability(firstDecl, BaseLoc, CS.DC,
/*call*/ nullptr))
return true;
}
return callback.hasValue() ? (*callback)(viableCandidatesToReport) : false;
}
bool FailureDiagnosis::visitUnresolvedDotExpr(UnresolvedDotExpr *UDE) {
auto *baseExpr = UDE->getBase();
auto *locator = CS.getConstraintLocator(UDE, ConstraintLocator::Member);
if (!locator)
return false;
return diagnoseMemberFailures(UDE, baseExpr, ConstraintKind::ValueMember,
UDE->getName(), UDE->getFunctionRefKind(),
locator);
}
/// An IdentityExpr doesn't change its argument, but it *can* propagate its
/// contextual type information down.
bool FailureDiagnosis::visitIdentityExpr(IdentityExpr *E) {
auto contextualType = CS.getContextualType();
// If we have a paren expr and our contextual type is a ParenType, remove the
// paren expr sugar.
if (contextualType)
contextualType = contextualType->getWithoutParens();
if (!typeCheckChildIndependently(E->getSubExpr(), contextualType,
CS.getContextualTypePurpose()))
return true;
return false;
}
/// A TryExpr doesn't change it's argument, nor does it change the contextual
/// type.
bool FailureDiagnosis::visitTryExpr(TryExpr *E) {
return visit(E->getSubExpr());
}
bool FailureDiagnosis::visitExpr(Expr *E) {
// Check each of our immediate children to see if any of them are
// independently invalid.
bool errorInSubExpr = false;
E->forEachImmediateChildExpr([&](Expr *Child) -> Expr* {
// If we already found an error, stop checking.
if (errorInSubExpr) return Child;
// Otherwise just type check the subexpression independently. If that
// succeeds, then we stitch the result back into our expression.
if (typeCheckChildIndependently(Child, TCC_AllowLValue))
return Child;
// Otherwise, it failed, which emitted a diagnostic. Keep track of this
// so that we don't emit multiple diagnostics.
errorInSubExpr = true;
return Child;
});
// If any of the children were errors, we're done.
if (errorInSubExpr)
return true;
// Otherwise, produce a more generic error.
return false;
}
bool FailureDiagnosis::diagnoseExprFailure() {
assert(expr);
// Our general approach is to do a depth first traversal of the broken
// expression tree, type checking as we go. If we find a subtree that cannot
// be type checked on its own (even to an incomplete type) then that is where
// we focus our attention. If we do find a type, we use it to check for
// contextual type mismatches.
return visit(expr);
}
/// Given a specific expression and the remnants of the failed constraint
/// system, produce a specific diagnostic.
///
/// This is guaranteed to always emit an error message.
///
void ConstraintSystem::diagnoseFailureForExpr(Expr *expr) {
setPhase(ConstraintSystemPhase::Diagnostics);
SWIFT_DEFER { setPhase(ConstraintSystemPhase::Finalization); };
// Look through RebindSelfInConstructorExpr to avoid weird Sema issues.
if (auto *RB = dyn_cast<RebindSelfInConstructorExpr>(expr))
expr = RB->getSubExpr();
FailureDiagnosis diagnosis(expr, *this);
// Now, attempt to diagnose the failure from the info we've collected.
if (diagnosis.diagnoseExprFailure())
return;
// If this is a contextual conversion problem, dig out some information.
if (diagnosis.diagnoseContextualConversionError(expr, getContextualType(),
getContextualTypePurpose()))
return;
// If no one could find a problem with this expression or constraint system,
// then it must be well-formed... but is ambiguous. Handle this by diagnostic
// various cases that come up.
diagnosis.diagnoseAmbiguity(expr);
}
std::pair<Type, ContextualTypePurpose>
FailureDiagnosis::validateContextualType(Type contextualType,
ContextualTypePurpose CTP) {
if (!contextualType)
return {contextualType, CTP};
// Since some of the contextual types might be tuples e.g. subscript argument
// is a tuple or paren wrapping a tuple, it's required to recursively check
// its elements to determine nullability of the contextual type, because it
// might contain archetypes.
std::function<bool(Type)> shouldNullifyType = [&](Type type) -> bool {
switch (type->getDesugaredType()->getKind()) {
case TypeKind::PrimaryArchetype:
case TypeKind::OpenedArchetype:
case TypeKind::NestedArchetype:
case TypeKind::Unresolved:
return true;
case TypeKind::BoundGenericEnum:
case TypeKind::BoundGenericClass:
case TypeKind::BoundGenericStruct:
case TypeKind::UnboundGeneric:
case TypeKind::GenericFunction:
case TypeKind::Metatype:
return type->hasUnresolvedType();
case TypeKind::Tuple: {
auto tupleType = type->getAs<TupleType>();
for (auto &element : tupleType->getElements()) {
if (shouldNullifyType(element.getType()))
return true;
}
break;
}
default:
return false;
}
return false;
};
bool shouldNullify = false;
if (auto objectType = contextualType->getWithoutSpecifierType()) {
// Note that simply checking for `objectType->hasUnresolvedType()` is not
// appropriate in this case standalone, because if it's in a function,
// for example, or inout type, we still want to preserve it's skeleton
/// because that helps to diagnose inout argument issues. Complete
// nullification is only appropriate for generic types with unresolved
// types or standalone archetypes because that's going to give
// sub-expression solver a chance to try and compute type as it sees fit
// and higher level code would have a chance to check it, which avoids
// diagnostic messages like `cannot convert (_) -> _ to (Int) -> Void`.
shouldNullify = shouldNullifyType(objectType);
}
// If the conversion type contains no info, drop it.
if (shouldNullify)
return {Type(), CTP_Unused};
// Remove all of the potentially leftover type variables or type parameters
// from the contextual type to be used by new solver.
contextualType = replaceTypeParametersWithUnresolved(contextualType);
contextualType = replaceTypeVariablesWithUnresolved(contextualType);
return {contextualType, CTP};
}
/// Check the specified closure to see if it is a multi-statement closure with
/// an uninferred type. If so, diagnose the problem with an error and return
/// true.
bool FailureDiagnosis::
diagnoseAmbiguousMultiStatementClosure(ClosureExpr *closure) {
if (closure->hasSingleExpressionBody() ||
closure->hasExplicitResultType())
return false;
auto closureType = CS.getType(closure)->getAs<AnyFunctionType>();
if (!closureType ||
!(closureType->getResult()->hasUnresolvedType() ||
closureType->getResult()->hasTypeVariable()))
return false;
// Okay, we have a multi-statement closure expr that has no inferred result,
// type, in the context of a larger expression. The user probably expected
// the compiler to infer the result type of the closure from the body of the
// closure, which Swift doesn't do for multi-statement closures. Try to be
// helpful by digging into the body of the closure, looking for a return
// statement, and inferring the result type from it. If we can figure that
// out, we can produce a fixit hint.
class ReturnStmtFinder : public ASTWalker {
SmallVectorImpl<ReturnStmt*> &returnStmts;
public:
ReturnStmtFinder(SmallVectorImpl<ReturnStmt*> &returnStmts)
: returnStmts(returnStmts) {}
// Walk through statements, so we find returns hiding in if/else blocks etc.
std::pair<bool, Stmt *> walkToStmtPre(Stmt *S) override {
// Keep track of any return statements we find.
if (auto RS = dyn_cast<ReturnStmt>(S))
returnStmts.push_back(RS);
return { true, S };
}
// Don't walk into anything else, since they cannot contain statements
// that can return from the current closure.
std::pair<bool, Expr *> walkToExprPre(Expr *E) override {
return { false, E };
}
std::pair<bool, Pattern*> walkToPatternPre(Pattern *P) override {
return { false, P };
}
bool walkToDeclPre(Decl *D) override { return false; }
bool walkToTypeLocPre(TypeLoc &TL) override { return false; }
bool walkToTypeReprPre(TypeRepr *T) override { return false; }
bool walkToParameterListPre(ParameterList *PL) override { return false; }
};
SmallVector<ReturnStmt*, 4> Returns;
closure->getBody()->walk(ReturnStmtFinder(Returns));
// If we found a return statement inside of the closure expression, then go
// ahead and type check the body to see if we can determine a type.
for (auto RS : Returns) {
llvm::SaveAndRestore<DeclContext *> SavedDC(CS.DC, closure);
// Otherwise, we're ok to type check the subexpr.
Type resultType;
if (RS->hasResult()) {
auto resultExpr = RS->getResult();
ConcreteDeclRef decl = nullptr;
// If return expression uses closure parameters, which have/are
// type variables, such means that we won't be able to
// type-check result correctly and, unfortunately,
// we are going to leak type variables from the parent
// constraint system through declaration types.
bool hasUnresolvedParams = false;
resultExpr->forEachChildExpr([&](Expr *childExpr) -> Expr *{
if (auto DRE = dyn_cast<DeclRefExpr>(childExpr)) {
if (auto param = dyn_cast<ParamDecl>(DRE->getDecl())) {
auto paramType =
param->hasInterfaceType() ? param->getType() : Type();
if (!paramType || paramType->hasTypeVariable()) {
hasUnresolvedParams = true;
return nullptr;
}
}
}
return childExpr;
});
if (hasUnresolvedParams)
continue;
ConstraintSystem::preCheckExpression(resultExpr, CS.DC, &CS);
// Obtain type of the result expression without applying solutions,
// because otherwise this might result in leaking of type variables,
// since we are not resetting result statement and if expression is
// successfully type-checked its type cleanup is going to be disabled
// (we are allowing unresolved types), and as a side-effect it might
// also be transformed e.g. OverloadedDeclRefExpr -> DeclRefExpr.
auto type = TypeChecker::getTypeOfExpressionWithoutApplying(
resultExpr, CS.DC, decl, FreeTypeVariableBinding::UnresolvedType);
if (type)
resultType = type->getRValueType();
}
// If we found a type, presuppose it was the intended result and insert a
// fixit hint.
if (resultType && !isUnresolvedOrTypeVarType(resultType)) {
// If there is a location for an 'in' token, then the argument list was
// specified somehow but no return type was. Insert a "-> ReturnType "
// before the in token.
if (closure->getInLoc().isValid()) {
diagnose(closure->getLoc(), diag::cannot_infer_closure_result_type)
.fixItInsert(closure->getInLoc(), diag::insert_closure_return_type,
resultType, /*argListSpecified*/ false);
return true;
}
// Otherwise, the closure must take zero arguments. We know this
// because the if one or more argument is specified, a multi-statement
// closure *must* name them, or explicitly ignore them with "_ in".
//
// As such, we insert " () -> ReturnType in " right after the '{' that
// starts the closure body.
diagnose(closure->getLoc(), diag::cannot_infer_closure_result_type)
.fixItInsertAfter(closure->getBody()->getLBraceLoc(),
diag::insert_closure_return_type, resultType,
/*argListSpecified*/ true);
return true;
}
}
diagnose(closure->getLoc(), diag::cannot_infer_closure_result_type);
return true;
}
/// Emit an ambiguity diagnostic about the specified expression.
void FailureDiagnosis::diagnoseAmbiguity(Expr *E) {
if (auto *assignment = dyn_cast<AssignExpr>(E)) {
if (isa<DiscardAssignmentExpr>(assignment->getDest())) {
auto *srcExpr = assignment->getSrc();
bool diagnosedInvalidUseOfDiscardExpr = false;
srcExpr->forEachChildExpr([&](Expr *expr) -> Expr * {
if (auto *DAE = dyn_cast<DiscardAssignmentExpr>(expr)) {
diagnose(DAE->getLoc(), diag::discard_expr_outside_of_assignment)
.highlight(srcExpr->getSourceRange());
diagnosedInvalidUseOfDiscardExpr = true;
return nullptr;
}
return expr;
});
if (diagnosedInvalidUseOfDiscardExpr)
return;
diagnoseAmbiguity(srcExpr);
return;
}
}
// Unresolved/Anonymous ClosureExprs are common enough that we should give
// them tailored diagnostics.
if (auto CE = dyn_cast<ClosureExpr>(E->getValueProvidingExpr())) {
// If this is a multi-statement closure with no explicit result type, emit
// a note to clue the developer in.
if (diagnoseAmbiguousMultiStatementClosure(CE))
return;
diagnose(E->getLoc(), diag::cannot_infer_closure_type)
.highlight(E->getSourceRange());
return;
}
// A DiscardAssignmentExpr (spelled "_") needs contextual type information to
// infer its type. If we see one at top level, diagnose that it must be part
// of an assignment so we don't get a generic "expression is ambiguous" error.
if (isa<DiscardAssignmentExpr>(E)) {
diagnose(E->getLoc(), diag::discard_expr_outside_of_assignment)
.highlight(E->getSourceRange());
return;
}
// Diagnose ".foo" expressions that lack context specifically.
if (auto UME =
dyn_cast<UnresolvedMemberExpr>(E->getSemanticsProvidingExpr())) {
if (!CS.getContextualType()) {
diagnose(E->getLoc(), diag::unresolved_member_no_inference,UME->getName())
.highlight(SourceRange(UME->getDotLoc(),
UME->getNameLoc().getSourceRange().End));
return;
}
}
// Diagnose empty collection literals that lack context specifically.
if (auto CE = dyn_cast<CollectionExpr>(E->getSemanticsProvidingExpr())) {
if (CE->getNumElements() == 0) {
diagnose(E->getLoc(), diag::unresolved_collection_literal)
.highlight(E->getSourceRange());
return;
}
}
// Diagnose 'nil' without a contextual type.
if (isa<NilLiteralExpr>(E->getSemanticsProvidingExpr())) {
diagnose(E->getLoc(), diag::unresolved_nil_literal)
.highlight(E->getSourceRange());
return;
}
// A very common cause of this diagnostic is a situation where a closure expr
// has no inferred type, due to being a multiline closure. Check to see if
// this is the case and (if so), speculatively diagnose that as the problem.
bool didDiagnose = false;
E->forEachChildExpr([&](Expr *subExpr) -> Expr*{
auto closure = dyn_cast<ClosureExpr>(subExpr);
if (!didDiagnose && closure)
didDiagnose = diagnoseAmbiguousMultiStatementClosure(closure);
return subExpr;
});
if (didDiagnose) return;
// Attempt to re-type-check the entire expression, allowing ambiguity, but
// ignoring a contextual type.
if (expr == E) {
auto exprType = getTypeOfTypeCheckedChildIndependently(expr);
// If it failed and diagnosed something, then we're done.
if (!exprType) return;
// If we were able to find something more specific than "unknown" (perhaps
// something like "[_:_]" for a dictionary literal), include it in the
// diagnostic.
if (!isUnresolvedOrTypeVarType(exprType)) {
diagnose(E->getLoc(), diag::specific_type_of_expression_is_ambiguous,
exprType)
.highlight(E->getSourceRange());
return;
}
}
// Before giving up completely let's try to see if there are any
// fixes recorded by constraint generator, which point to structural
// problems that might not result in solution even if fixed e.g.
// missing members involved in protocol composition in expression
// context which are interpreted as binary operator expressions instead.
{
bool diagnosed = false;
for (auto *fix : CS.getFixes())
diagnosed |= fix->diagnose();
if (diagnosed)
return;
}
// If there are no posted constraints or failures, then there was
// not enough contextual information available to infer a type for the
// expression.
diagnose(E->getLoc(), diag::type_of_expression_is_ambiguous)
.highlight(E->getSourceRange());
}
/// If an UnresolvedDotExpr, SubscriptMember, etc has been resolved by the
/// constraint system, return the decl that it references.
ValueDecl *ConstraintSystem::findResolvedMemberRef(ConstraintLocator *locator) {
// See if we have a resolution for this member.
auto overload = findSelectedOverloadFor(locator);
if (!overload)
return nullptr;
// We only want to handle the simplest decl binding.
auto choice = overload->choice;
if (choice.getKind() != OverloadChoiceKind::Decl)
return nullptr;
return choice.getDecl();
}
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