[clang] [Index] The requirements are not handled when generates USR for `TemplateDecl`

[16bit-ykiko]

Consider following example:

template <typename T, typename U>
struct function;

template <typename T, typename U>
    requires (__is_same(U, int))
struct function<T, U> {
    void foo();
};

template <typename T, typename U>
    requires (__is_same(U, float))
struct function<T, U> {
    void foo();
};

The second specialization and third specialization should have different USR, but actually same

c:@SP>2#T#T@function>#t0.0#t0.1
c:@SP>2#T#T@function>#t0.0#t0.1

Thie is beacuse the USRGenerator doesn't handle requirements in TemplateDecl. See

llvm-project/clang/lib/Index/USRGeneration.cpp

Lines 352 to 361 in caeefe7

	if (const VarTemplateSpecializationDecl *Spec
	= dyn_cast<VarTemplateSpecializationDecl>(D)) {
	const TemplateArgumentList &Args = Spec->getTemplateArgs();
	Out << '>';
	for (unsigned I = 0, N = Args.size(); I != N; ++I) {
	Out << '#';
	VisitTemplateArgument(Args.get(I));
	}
	}
	}

[sakria9]

To handle requires, the expression need to be encoded into the USR, which may result a long USR. Is this acceptable?

[16bit-ykiko]

To handle requires, the expression need to be encoded into the USR, which may result a long USR. Is this acceptable?

Yes it is expected.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: ykiko (16bit-ykiko)

Consider following example:

template <typename T, typename U>
struct function;

template <typename T, typename U>
    requires (__is_same(U, int))
struct function<T, U> {
    void foo();
};

template <typename T, typename U>
    requires (__is_same(U, float))
struct function<T, U> {
    void foo();
};

The second specialization and third specialization should have different USR, but actually same

c:@<!-- -->SP&gt;2#T#T@<!-- -->function&gt;#t0.0#t0.1
c:@<!-- -->SP&gt;2#T#T@<!-- -->function&gt;#t0.0#t0.1

Thie is beacuse the USRGenerator doesn't handle requirements in TemplateDecl. See

llvm-project/clang/lib/Index/USRGeneration.cpp

Lines 352 to 361 in caeefe7

	if (const VarTemplateSpecializationDecl *Spec
	= dyn_cast<VarTemplateSpecializationDecl>(D)) {
	const TemplateArgumentList &Args = Spec->getTemplateArgs();
	Out << '>';
	for (unsigned I = 0, N = Args.size(); I != N; ++I) {
	Out << '#';
	VisitTemplateArgument(Args.get(I));
	}
	}
	}