Clang accepts invalid code that mutates a const parameter when it is defined with a 'const' qualifier but declared without the 'const' in a class template

[hyp]

Bugzilla Link	31607
Version	trunk
OS	All
CC	@DougGregor

Extended Description

Clang fails to report an error that it "cannot assign to variable 'b' with const-qualified type" given the following piece of code:

template
struct A
{
struct B {};

const B* test (const B* b) const;

};

template
inline auto A< T >::test (const B* const b) const -> const B*
{
return ++b; // expected an error here
}

int main()
{
A<> m;
const A<>::B* b = 0;
b = m.test (b);
}

The AST dumps show that the specialisation of method test from class A has the following parameter declaration:

ParmVarDecl 0x7fba11802228 <col:17, col:26> col:26 used b 'const struct A::B *'

but the non-specialised definition of the method test has the following parameter declaration:

ParmVarDecl 0x7fba11800e90 <col:27, col:42> col:42 referenced b 'const struct A::B *const'

This makes me think that the error isn't reported because the 'const' qualifier isn't given to the parameter in the specialised method definition.

[wheatman]

This behavior is still the same is post 17 trunk(8a62d6b)
https://godbolt.org/z/ebq8oW6jz

code

template<class T = int>
struct A
{
	struct B {};

	const B* test (const B* b) const;
};

template<class T>
inline auto A< T >::test (const B* const b) const -> const B*
{
	return ++b; // expected an error here
}

int main()
{
    A<> m;
    const A<>::B* b = 0;
    b = m.test (b);
}

gcc error

<source>: In instantiation of 'const A<T>::B* A<T>::test(const B*) const [with T = int]':
<source>:19:16:   required from here
<source>:12:18: error: increment of read-only parameter 'b'
   12 |         return ++b; // expected an error here
      |                  ^
Compiler returned: 1

[llvmbot]

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