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[clang] Don't emit redundant warnings for 'return;'

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when the function declaration's return type is already invalid for
some reason. This is relevant to https://github.com/llvm/llvm-project/issues/49188
because another way that the declaration's return type could become
invalid is that it might be `C auto` where `C<void>` is false.

Differential Revision: https://reviews.llvm.org/D119094
This commit is contained in:
Arthur O'Dwyer 2022-02-06 16:40:28 -05:00
parent 528deedd58
commit 3c8d2aa87c
2 changed files with 26 additions and 1 deletions
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4
clang/lib/Sema/SemaStmt.cpp
View file

@ -4098,7 +4098,9 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
} else if (!RetValExp && !HasDependentReturnType) {
FunctionDecl *FD = getCurFunctionDecl();
if (getLangOpts().CPlusPlus11 && FD && FD->isConstexpr()) {
if ((FD && FD->isInvalidDecl()) || FnRetType->containsErrors()) {
// The intended return type might have been "void", so don't warn.
} else if (getLangOpts().CPlusPlus11 && FD && FD->isConstexpr()) {
// C++11 [stmt.return]p2
Diag(ReturnLoc, diag::err_constexpr_return_missing_expr)
<< FD << FD->isConsteval();

23
clang/test/SemaCXX/deduced-return-void.cpp Normal file
View file

@ -0,0 +1,23 @@
// RUN: %clang_cc1 -std=c++14 -fsyntax-only -verify %s
// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify %s
// Check that we don't get any extra warning for "return" without an
// expression, in a function that might have been intended to return
// void all along.
auto f1() {
return 1;
return; // expected-error {{deduced as 'void' here but deduced as 'int' in earlier return statement}}
}
decltype(auto) f2() {
return 1;
return; // expected-error {{deduced as 'void' here but deduced as 'int' in earlier return statement}}
}
auto *g() {
return; // expected-error {{cannot deduce return type 'auto *' from omitted return expression}}
}
decltype(h1) h1() { // expected-error {{use of undeclared identifier 'h1'}}
return;
}