Clang accepts invalid code: `int field<0, 1, int>;`

[jcelerier]

Repro: https://gcc.godbolt.org/z/7rhq5Wvbe

struct foo {
  int field<0, 1, int, 3>;
};

the above compiles and runs starting from clang-9 up to current git HEAD.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

[cor3ntin]

PR: https://reviews.llvm.org/D120881

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Jean-Michaël Celerier (jcelerier)

Repro: https://gcc.godbolt.org/z/7rhq5Wvbe

struct foo {
  int field<0, 1, int, 3>;
};

the above compiles and runs starting from clang-9 up to current git HEAD.