In blocks, only pretend that enum constants have enum type if necessary.
In C, enum constants have the type of the enum's underlying integer type,
rather than the type of the enum. (This is not true in C++.) Thus, when a
block's return type is inferred from an enum constant, it is incompatible
with expressions that return the enum type.
In r158899, I told block returns to pretend that enum constants have enum
type, like in C++. Doug Gregor pointed out that this can break existing code.
Now, we don't check the types of return statements until the end of the block.
This lets us go back and add implicit casts in blocks with mixed enum
constants and enum-typed expressions.
<rdar://problem/11662489> (again)
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@159591 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaLambda.cpp b/lib/Sema/SemaLambda.cpp
index 07ee890..6c78d83 100644
--- a/lib/Sema/SemaLambda.cpp
+++ b/lib/Sema/SemaLambda.cpp
@@ -214,6 +214,141 @@
}
}
+static bool checkReturnValueType(const ASTContext &Ctx, const Expr *E,
+ QualType &DeducedType,
+ QualType &AlternateType) {
+ // Handle ReturnStmts with no expressions.
+ if (!E) {
+ if (AlternateType.isNull())
+ AlternateType = Ctx.VoidTy;
+
+ return Ctx.hasSameType(DeducedType, Ctx.VoidTy);
+ }
+
+ QualType StrictType = E->getType();
+ QualType LooseType = StrictType;
+
+ // In C, enum constants have the type of their underlying integer type,
+ // not the enum. When inferring block return types, we should allow
+ // the enum type if an enum constant is used, unless the enum is
+ // anonymous (in which case there can be no variables of its type).
+ if (!Ctx.getLangOpts().CPlusPlus) {
+ const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts());
+ if (DRE) {
+ const Decl *D = DRE->getDecl();
+ if (const EnumConstantDecl *ECD = dyn_cast<EnumConstantDecl>(D)) {
+ const EnumDecl *Enum = cast<EnumDecl>(ECD->getDeclContext());
+ if (Enum->getDeclName() || Enum->getTypedefNameForAnonDecl())
+ LooseType = Ctx.getTypeDeclType(Enum);
+ }
+ }
+ }
+
+ // Special case for the first return statement we find.
+ // The return type has already been tentatively set, but we might still
+ // have an alternate type we should prefer.
+ if (AlternateType.isNull())
+ AlternateType = LooseType;
+
+ if (Ctx.hasSameType(DeducedType, StrictType)) {
+ // FIXME: The loose type is different when there are constants from two
+ // different enums. We could consider warning here.
+ if (AlternateType != Ctx.DependentTy)
+ if (!Ctx.hasSameType(AlternateType, LooseType))
+ AlternateType = Ctx.VoidTy;
+ return true;
+ }
+
+ if (Ctx.hasSameType(DeducedType, LooseType)) {
+ // Use DependentTy to signal that we're using an alternate type and may
+ // need to add casts somewhere.
+ AlternateType = Ctx.DependentTy;
+ return true;
+ }
+
+ if (Ctx.hasSameType(AlternateType, StrictType) ||
+ Ctx.hasSameType(AlternateType, LooseType)) {
+ DeducedType = AlternateType;
+ // Use DependentTy to signal that we're using an alternate type and may
+ // need to add casts somewhere.
+ AlternateType = Ctx.DependentTy;
+ return true;
+ }
+
+ return false;
+}
+
+void Sema::deduceClosureReturnType(CapturingScopeInfo &CSI) {
+ assert(CSI.HasImplicitReturnType);
+
+ // First case: no return statements, implicit void return type.
+ ASTContext &Ctx = getASTContext();
+ if (CSI.Returns.empty()) {
+ // It's possible there were simply no /valid/ return statements.
+ // In this case, the first one we found may have at least given us a type.
+ if (CSI.ReturnType.isNull())
+ CSI.ReturnType = Ctx.VoidTy;
+ return;
+ }
+
+ // Second case: at least one return statement has dependent type.
+ // Delay type checking until instantiation.
+ assert(!CSI.ReturnType.isNull() && "We should have a tentative return type.");
+ if (CSI.ReturnType->isDependentType())
+ return;
+
+ // Third case: only one return statement. Don't bother doing extra work!
+ SmallVectorImpl<ReturnStmt*>::iterator I = CSI.Returns.begin(),
+ E = CSI.Returns.end();
+ if (I+1 == E)
+ return;
+
+ // General case: many return statements.
+ // Check that they all have compatible return types.
+ // For now, that means "identical", with an exception for enum constants.
+ // (In C, enum constants have the type of their underlying integer type,
+ // not the type of the enum. C++ uses the type of the enum.)
+ QualType AlternateType;
+
+ // We require the return types to strictly match here.
+ for (; I != E; ++I) {
+ const ReturnStmt *RS = *I;
+ const Expr *RetE = RS->getRetValue();
+ if (!checkReturnValueType(Ctx, RetE, CSI.ReturnType, AlternateType)) {
+ // FIXME: This is a poor diagnostic for ReturnStmts without expressions.
+ Diag(RS->getLocStart(),
+ diag::err_typecheck_missing_return_type_incompatible)
+ << (RetE ? RetE->getType() : Ctx.VoidTy) << CSI.ReturnType
+ << isa<LambdaScopeInfo>(CSI);
+ // Don't bother fixing up the return statements in the block if some of
+ // them are unfixable anyway.
+ AlternateType = Ctx.VoidTy;
+ // Continue iterating so that we keep emitting diagnostics.
+ }
+ }
+
+ // If our return statements turned out to be compatible, but we needed to
+ // pick a different return type, go through and fix the ones that need it.
+ if (AlternateType == Ctx.DependentTy) {
+ for (SmallVectorImpl<ReturnStmt*>::iterator I = CSI.Returns.begin(),
+ E = CSI.Returns.end();
+ I != E; ++I) {
+ ReturnStmt *RS = *I;
+ Expr *RetE = RS->getRetValue();
+ if (RetE->getType() == CSI.ReturnType)
+ continue;
+
+ // Right now we only support integral fixup casts.
+ assert(CSI.ReturnType->isIntegralOrUnscopedEnumerationType());
+ assert(RetE->getType()->isIntegralOrUnscopedEnumerationType());
+ ExprResult Casted = ImpCastExprToType(RetE, CSI.ReturnType,
+ CK_IntegralCast);
+ assert(Casted.isUsable());
+ RS->setRetValue(Casted.take());
+ }
+ }
+}
+
void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
Declarator &ParamInfo,
Scope *CurScope) {
@@ -659,6 +794,8 @@
// denotes the following type:
// FIXME: Assumes current resolution to core issue 975.
if (LSI->HasImplicitReturnType) {
+ deduceClosureReturnType(*LSI);
+
// - if there are no return statements in the
// compound-statement, or all return statements return
// either an expression of type void or no expression or