Clang accepts declaration in a statement other than a compound statement

[AaronBallman]

The following code is grammatically incorrect:

void func() {
  if (1)
    int x;
}

because an iteratation statement must be followed by a secondary-block, which is a kind of statement, which does not accept declarations accept as allowed by compound-statement. GCC properly rejects this code as did Clang 17, so this is a recent regression: https://godbolt.org/z/sj3de1T74

[llvmbot]

@llvm/issue-subscribers-c

Author: Aaron Ballman (AaronBallman)

The following code is grammatically incorrect: ``` void func() { if (1) int x; } ``` because an iteratation statement must be followed by a secondary-block, which is a kind of statement, which does not accept declarations accept as allowed by compound-statement. GCC properly rejects this code as did Clang 17, so this is a recent regression: https://godbolt.org/z/sj3de1T74

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Aaron Ballman (AaronBallman)

The following code is grammatically incorrect: ``` void func() { if (1) int x; } ``` because an iteratation statement must be followed by a secondary-block, which is a kind of statement, which does not accept declarations accept as allowed by compound-statement. GCC properly rejects this code as did Clang 17, so this is a recent regression: https://godbolt.org/z/sj3de1T74

[jrtc27]

Bisected to 8bd06d5, which seems plausible