[Clang][Index] Add support for dependent class scope explicit specializations of function templates to USRGenerator (#98027)

Given the following:
```
template<typename T>
struct A
{
    void f(int); // #1
    
    template<typename U>
    void f(U); // #2
    
    template<>
    void f<int>(int); // #3
};
```
Clang will generate the same USR for `#1` and `#2`. This patch fixes the
issue by including the template arguments of dependent class scope
explicit specializations in their USRs.

1 files changed, 15 insertions, 0 deletions

diff --git a/clang/test/Index/USR/func-template.cpp b/clang/test/Index/USR/func-template.cpp
new file mode 100644
index 0000000..c9c82f5
--- /dev/null
+++ b/clang/test/Index/USR/func-template.cpp
@@ -0,0 +1,15 @@
+// RUN: c-index-test core -print-source-symbols -- %s | FileCheck %s
+
+template<typename T>
+struct A {
+  void f(int);
+  // CHECK: {{[0-9]+}}:8 | instance-method/C++ | f | c:@ST>1#T@A@F@f#I# |
+  
+  template<typename U>
+  void f(U);
+  // CHECK: {{[0-9]+}}:8 | instance-method/C++ | f | c:@ST>1#T@A@FT@>1#Tf#t1.0#v# |
+  
+  template<>
+  void f<int>(int);
+  // CHECK: {{[0-9]+}}:8 | instance-method/C++ | f | c:@ST>1#T@A@F@f<#I>#I# |
+};