swift-mirror/lib/Sema/ConstraintLocator.cpp

//===--- ConstraintLocator.cpp - Constraint Locator -----------------------===//
//
// 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 the \c ConstraintLocator class and its related types,
// which is used by the constraint-based type checker to describe how
// a particular constraint was derived.
//
//===----------------------------------------------------------------------===//
#include "ConstraintLocator.h"
#include "ConstraintSystem.h"
#include "swift/AST/Decl.h"
#include "swift/AST/Expr.h"
#include "swift/AST/Types.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/raw_ostream.h"

using namespace swift;
using namespace constraints;

void ConstraintLocator::Profile(llvm::FoldingSetNodeID &id, Expr *anchor,
                                ArrayRef<PathElement> path) {
  id.AddPointer(anchor);
  id.AddInteger(path.size());
  for (auto elt : path) {
    id.AddInteger(elt.getKind());
    switch (elt.getKind()) {
    case GenericParameter:
      id.AddPointer(elt.castTo<LocatorPathElt::GenericParameter>().getType());
      break;

    case ProtocolRequirement: {
      auto reqElt = elt.castTo<LocatorPathElt::ProtocolRequirement>();
      id.AddPointer(reqElt.getDecl());
      break;
    }

    case Witness:
      id.AddPointer(elt.castTo<LocatorPathElt::Witness>().getDecl());
      break;

    case KeyPathDynamicMember: {
      auto kpElt = elt.castTo<LocatorPathElt::KeyPathDynamicMember>();
      id.AddPointer(kpElt.getKeyPathDecl());
      break;
    }
    case GenericArgument:
    case NamedTupleElement:
    case TupleElement:
    case ApplyArgToParam:
    case OpenedGeneric:
    case KeyPathComponent:
    case ConditionalRequirement:
    case TypeParameterRequirement:
    case ContextualType:
    case SynthesizedArgument:
    case TernaryBranch: {
      auto numValues = numNumericValuesInPathElement(elt.getKind());
      for (unsigned i = 0; i < numValues; ++i)
        id.AddInteger(elt.getValue(i));
      break;
    }
#define SIMPLE_LOCATOR_PATH_ELT(Name) case Name :
#include "ConstraintLocatorPathElts.def"
    // Nothing to do for simple locator elements.
    break;
    }
  }
}

unsigned LocatorPathElt::getNewSummaryFlags() const {
  switch (getKind()) {
  case ConstraintLocator::ApplyArgument:
  case ConstraintLocator::ApplyFunction:
  case ConstraintLocator::SequenceElementType:
  case ConstraintLocator::ClosureResult:
  case ConstraintLocator::ConstructorMember:
  case ConstraintLocator::InstanceType:
  case ConstraintLocator::AutoclosureResult:
  case ConstraintLocator::OptionalPayload:
  case ConstraintLocator::Member:
  case ConstraintLocator::MemberRefBase:
  case ConstraintLocator::UnresolvedMember:
  case ConstraintLocator::ParentType:
  case ConstraintLocator::ExistentialSuperclassType:
  case ConstraintLocator::LValueConversion:
  case ConstraintLocator::RValueAdjustment:
  case ConstraintLocator::SubscriptMember:
  case ConstraintLocator::OpenedGeneric:
  case ConstraintLocator::GenericParameter:
  case ConstraintLocator::GenericArgument:
  case ConstraintLocator::NamedTupleElement:
  case ConstraintLocator::TupleElement:
  case ConstraintLocator::ProtocolRequirement:
  case ConstraintLocator::Witness:
  case ConstraintLocator::KeyPathComponent:
  case ConstraintLocator::ConditionalRequirement:
  case ConstraintLocator::TypeParameterRequirement:
  case ConstraintLocator::ImplicitlyUnwrappedDisjunctionChoice:
  case ConstraintLocator::DynamicLookupResult:
  case ConstraintLocator::ContextualType:
  case ConstraintLocator::SynthesizedArgument:
  case ConstraintLocator::KeyPathDynamicMember:
  case ConstraintLocator::KeyPathType:
  case ConstraintLocator::KeyPathRoot:
  case ConstraintLocator::KeyPathValue:
  case ConstraintLocator::KeyPathComponentResult:
  case ConstraintLocator::Condition:
  case ConstraintLocator::DynamicCallable:
  case ConstraintLocator::ImplicitCallAsFunction:
  case ConstraintLocator::TernaryBranch:
  case ConstraintLocator::PatternMatch:
    return 0;

  case ConstraintLocator::FunctionArgument:
  case ConstraintLocator::FunctionResult:
    return IsFunctionConversion;

  case ConstraintLocator::ApplyArgToParam: {
    auto flags = castTo<LocatorPathElt::ApplyArgToParam>().getParameterFlags();
    return flags.isNonEphemeral() ? IsNonEphemeralParam : 0;
  }
  }

  llvm_unreachable("Unhandled PathElementKind in switch.");
}

bool LocatorPathElt::isResultOfSingleExprFunction() const {
  if (auto elt = getAs<ContextualType>())
    return elt->isForSingleExprFunction();
  return false;
}

/// Determine whether given locator points to the subscript reference
/// e.g. `foo[0]` or `\Foo.[0]`
bool ConstraintLocator::isSubscriptMemberRef() const {
  auto *anchor = getAnchor();
  auto path = getPath();

  if (!anchor || path.empty())
    return false;

  return path.back().getKind() == ConstraintLocator::SubscriptMember;
}

bool ConstraintLocator::isKeyPathType() const {
  auto *anchor = getAnchor();
  auto path = getPath();
  // The format of locator should be `<keypath expr> -> key path type`
  if (!anchor || !isa<KeyPathExpr>(anchor) || path.size() != 1)
    return false;
  return path.back().getKind() == ConstraintLocator::KeyPathType;
}

bool ConstraintLocator::isKeyPathRoot() const {
  auto *anchor = getAnchor();
  auto path = getPath();

  if (!anchor || path.empty())
    return false;

  return path.back().getKind() == ConstraintLocator::KeyPathRoot;
}

bool ConstraintLocator::isKeyPathValue() const {
  auto *anchor = getAnchor();
  auto path = getPath();

  if (!anchor || path.empty())
    return false;

  return path.back().getKind() == ConstraintLocator::KeyPathValue;
}

bool ConstraintLocator::isResultOfKeyPathDynamicMemberLookup() const {
  return llvm::any_of(getPath(), [](const LocatorPathElt &elt) {
    return elt.isKeyPathDynamicMember();
  });
}

bool ConstraintLocator::isKeyPathSubscriptComponent() const {
  auto *anchor = getAnchor();
  auto *KPE = dyn_cast_or_null<KeyPathExpr>(anchor);
  if (!KPE)
    return false;

  using ComponentKind = KeyPathExpr::Component::Kind;
  return llvm::any_of(getPath(), [&](const LocatorPathElt &elt) {
    auto keyPathElt = elt.getAs<LocatorPathElt::KeyPathComponent>();
    if (!keyPathElt)
      return false;

    auto index = keyPathElt->getIndex();
    auto &component = KPE->getComponents()[index];
    return component.getKind() == ComponentKind::Subscript ||
           component.getKind() == ComponentKind::UnresolvedSubscript;
  });
}

bool ConstraintLocator::isForKeyPathDynamicMemberLookup() const {
  auto path = getPath();
  return !path.empty() && path.back().isKeyPathDynamicMember();
}

bool ConstraintLocator::isForKeyPathComponent() const {
  return llvm::any_of(getPath(), [&](const LocatorPathElt &elt) {
    return elt.isKeyPathComponent();
  });
}

bool ConstraintLocator::isForGenericParameter() const {
  return isLastElement<LocatorPathElt::GenericParameter>();
}

bool ConstraintLocator::isForSequenceElementType() const {
  return isLastElement<LocatorPathElt::SequenceElementType>();
}

bool ConstraintLocator::isForContextualType() const {
  return isLastElement<LocatorPathElt::ContextualType>();
}

bool ConstraintLocator::isForAssignment() const {
  auto *anchor = getAnchor();
  return anchor && isa<AssignExpr>(anchor) && getPath().empty();
}

bool ConstraintLocator::isForCoercion() const {
  auto *anchor = getAnchor();
  return anchor && isa<CoerceExpr>(anchor) && getPath().empty();
}

GenericTypeParamType *ConstraintLocator::getGenericParameter() const {
  // Check whether we have a path that terminates at a generic parameter.
  return isForGenericParameter() ?
      castLastElementTo<LocatorPathElt::GenericParameter>().getType() : nullptr;
}

void ConstraintLocator::dump(SourceManager *sm) const {
  dump(sm, llvm::errs());
  llvm::errs() << "\n";
}

void ConstraintLocator::dump(ConstraintSystem *CS) const {
  dump(&CS->getASTContext().SourceMgr, llvm::errs());
  llvm::errs() << "\n";
}


void ConstraintLocator::dump(SourceManager *sm, raw_ostream &out) const {
  PrintOptions PO;
  PO.PrintTypesForDebugging = true;
  
  out << "locator@" << (void*) this << " [";

  if (anchor) {
    out << Expr::getKindName(anchor->getKind());
    if (sm) {
      out << '@';
      anchor->getLoc().print(out, *sm);
    }
  }

  auto dumpReqKind = [&out](RequirementKind kind) {
    out << " (";
    switch (kind) {
    case RequirementKind::Conformance:
      out << "conformance";
      break;
    case RequirementKind::Superclass:
      out << "superclass";
      break;
    case RequirementKind::SameType:
      out << "same-type";
      break;
    case RequirementKind::Layout:
      out << "layout";
      break;
    }
    out << ")";
  };

  for (auto elt : getPath()) {
    out << " -> ";
    switch (elt.getKind()) {
    case GenericParameter: {
      auto gpElt = elt.castTo<LocatorPathElt::GenericParameter>();
      out << "generic parameter '" << gpElt.getType()->getString(PO) << "'";
      break;
    }
    case ApplyArgument:
      out << "apply argument";
      break;

    case ApplyFunction:
      out << "apply function";
      break;

    case OptionalPayload:
      out << "optional payload";
      break;

    case ApplyArgToParam: {
      auto argElt = elt.castTo<LocatorPathElt::ApplyArgToParam>();
      out << "comparing call argument #" << llvm::utostr(argElt.getArgIdx())
          << " to parameter #" << llvm::utostr(argElt.getParamIdx());
      if (argElt.getParameterFlags().isNonEphemeral())
        out << " (non-ephemeral)";
      break;
    }
    case ClosureResult:
      out << "closure result";
      break;

    case ConstructorMember:
      out << "constructor member";
      break;

    case FunctionArgument:
      out << "function argument";
      break;

    case FunctionResult:
      out << "function result";
      break;

    case SequenceElementType:
      out << "sequence element type";
      break;

    case GenericArgument: {
      auto genericElt = elt.castTo<LocatorPathElt::GenericArgument>();
      out << "generic argument #" << llvm::utostr(genericElt.getIndex());
      break;
    }
    case InstanceType:
      out << "instance type";
      break;

    case AutoclosureResult:
      out << "@autoclosure result";
      break;

    case Member:
      out << "member";
      break;

    case MemberRefBase:
      out << "member reference base";
      break;

    case NamedTupleElement: {
      auto tupleElt = elt.castTo<LocatorPathElt::NamedTupleElement>();
      out << "named tuple element #" << llvm::utostr(tupleElt.getIndex());
      break;
    }
    case UnresolvedMember:
      out << "unresolved member";
      break;
        
    case ParentType:
      out << "parent type";
      break;

    case ExistentialSuperclassType:
      out << "existential superclass type";
      break;

    case LValueConversion:
      out << "@lvalue-to-inout conversion";
      break;

    case RValueAdjustment:
      out << "rvalue adjustment";
      break;

    case SubscriptMember:
      out << "subscript member";
      break;

    case TupleElement: {
      auto tupleElt = elt.castTo<LocatorPathElt::TupleElement>();
      out << "tuple element #" << llvm::utostr(tupleElt.getIndex());
      break;
    }
    case KeyPathComponent: {
      auto kpElt = elt.castTo<LocatorPathElt::KeyPathComponent>();
      out << "key path component #" << llvm::utostr(kpElt.getIndex());
      break;
    }
    case ProtocolRequirement: {
      auto reqElt = elt.castTo<LocatorPathElt::ProtocolRequirement>();
      out << "protocol requirement ";
      reqElt.getDecl()->dumpRef(out);
      break;
    }
    case Witness: {
      auto witnessElt = elt.castTo<LocatorPathElt::Witness>();
      out << "witness ";
      witnessElt.getDecl()->dumpRef(out);
      break;
    }
    case OpenedGeneric:
      out << "opened generic";
      break;

    case ConditionalRequirement: {
      auto reqElt = elt.castTo<LocatorPathElt::ConditionalRequirement>();
      out << "conditional requirement #" << llvm::utostr(reqElt.getIndex());
      dumpReqKind(reqElt.getRequirementKind());
      break;
    }
    case TypeParameterRequirement: {
      auto reqElt = elt.castTo<LocatorPathElt::TypeParameterRequirement>();
      out << "type parameter requirement #" << llvm::utostr(reqElt.getIndex());
      dumpReqKind(reqElt.getRequirementKind());
      break;
    }

    case ImplicitlyUnwrappedDisjunctionChoice:
      out << "implicitly unwrapped disjunction choice";
      break;

    case DynamicLookupResult:
      out << "dynamic lookup result";
      break;

    case ContextualType:
      if (elt.isResultOfSingleExprFunction())
        out << "expected result type of the function with a single expression";
      else
        out << "contextual type";
      break;

    case SynthesizedArgument: {
      auto argElt = elt.castTo<LocatorPathElt::SynthesizedArgument>();
      out << "synthesized argument #" << llvm::utostr(argElt.getIndex());
      break;
    }
    case KeyPathDynamicMember:
      out << "key path dynamic member lookup";
      break;

    case KeyPathType:
      out << "key path type";
      break;

    case KeyPathRoot:
      out << "key path root";
      break;

    case KeyPathValue:
      out << "key path value";
      break;

    case KeyPathComponentResult:
      out << "key path component result";
      break;

    case Condition:
      out << "condition expression";
      break;

    case DynamicCallable:
      out << "implicit call to @dynamicCallable method";
      break;

    case ImplicitCallAsFunction:
      out << "implicit reference to callAsFunction";
      break;

    case TernaryBranch: {
      auto branchElt = elt.castTo<LocatorPathElt::TernaryBranch>();
      out << (branchElt.forThen() ? "'then'" : "'else'")
          << " branch of a ternary operator";
      break;
    }

    case PatternMatch:
      out << "pattern match";
      break;
    }
  }
  out << ']';
}