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Sema: Peephole for 'nil' literal of Optional type

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This commit is contained in:
Slava Pestov
2018-03-16 23:28:56 -07:00
parent fb499ca06d
commit d118654fa8
10 changed files with 79 additions and 42 deletions
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47
lib/Sema/MiscDiagnostics.cpp
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@@ -1423,27 +1423,42 @@ static void diagSyntacticUseRestrictions(TypeChecker &TC, const Expr *E,
}
/// Return true if this is 'nil' type checked as an Optional. This looks
/// like this:
/// (call_expr implicit type='Int?'
/// (constructor_ref_call_expr implicit
/// (declref_expr implicit decl=Optional.init(nilLiteral:)
static bool isTypeCheckedOptionalNil(Expr *E) {
auto CE = dyn_cast<CallExpr>(E->getSemanticsProvidingExpr());
/// Return true if this is a 'nil' literal. This looks
/// like this if the type is Optional<T>:
///
/// (dot_syntax_call_expr implicit type='Int?'
/// (declref_expr implicit decl=Optional.none)
/// (type_expr type=Int?))
///
/// Or like this if it is any other ExpressibleByNilLiteral type:
///
/// (dot_syntax_call_expr implicit type='Int?'
/// (declref_expr implicit decl=Optional.none)
/// (type_expr type=Int?))
///
bool isTypeCheckedOptionalNil(Expr *E) {
auto CE = dyn_cast<ApplyExpr>(E->getSemanticsProvidingExpr());
if (!CE || !CE->isImplicit())
return false;
// First case -- Optional.none
if (auto DRE = dyn_cast<DeclRefExpr>(CE->getSemanticFn()))
return DRE->getDecl() == TC.Context.getOptionalNoneDecl();
// Second case -- init(nilLiteral:)
auto CRCE = dyn_cast<ConstructorRefCallExpr>(CE->getSemanticFn());
if (!CRCE || !CRCE->isImplicit()) return false;
auto DRE = dyn_cast<DeclRefExpr>(CRCE->getSemanticFn());
SmallString<32> NameBuffer;
auto name = DRE->getDecl()->getFullName().getString(NameBuffer);
return name == "init(nilLiteral:)";
if (auto DRE = dyn_cast<DeclRefExpr>(CRCE->getSemanticFn())) {
SmallString<32> NameBuffer;
auto name = DRE->getDecl()->getFullName().getString(NameBuffer);
return name == "init(nilLiteral:)";
}
return false;
}
/// Warn about surprising implicit optional promotions involving operands to
/// calls. Specifically, we warn about these expressions when the 'x'
/// operand is implicitly promoted to optional: