================
@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++14 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++17 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++20 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++23 %s
+
+// Test that 'auto' cannot be combined with a type specifier in C++.
+void f() {
+ auto int x = 1; // expected-error {{'auto' cannot be combined with a
type specifier}}
----------------
AaronBallman wrote:
> Can someone clarify why we would need new annotation or tentative parsing
> here? It seems to me that we can handle `auto` incrementally while building
> the list of decl specifiers without any novel lookahead, and I thought that's
> what we already did. I would expect that we're just converting an extension
> warning to an error here, and then doing some simplification if we can.
The current logic does: `if (isKnownToBeTypeSpecifier(GetLookAheadToken(1))) {`
and this fails with:
```
template <typename Ty>
void g() {
auto Ty x;
}
```
because the token we get from lookahead is `identifier` for `Ty`. We do not
know that `Ty` is a type unless we do the annotation dance. Are you suggesting
the better approach is to wait until `DeclSpec::Finish()` and determine it's
invalid then?
> We know Ty is a type,
We only know that after we do the annotation, unless I'm missing something.
https://github.com/llvm/llvm-project/pull/166004
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