[clang] [clang][Index] Use canonical function parameter types in USRs (PR #68222)

[Krystian Stasiowski via cfe-commits]

https://github.com/sdkrystian updated https://github.com/llvm/llvm-project/pull/68222

>From 8022677bd92d4074ccaebda687f43066ce33d152 Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Wed, 4 Oct 2023 10:06:28 -0400
Subject: [PATCH 1/2] [clang][Index] Use canonical function parameter types in
 USRs

---
 clang/lib/Index/USRGeneration.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Index/USRGeneration.cpp b/clang/lib/Index/USRGeneration.cpp
index 5acc86191f8f9c..31c4a3345c09d1 100644
--- a/clang/lib/Index/USRGeneration.cpp
+++ b/clang/lib/Index/USRGeneration.cpp
@@ -267,10 +267,13 @@ void USRGenerator::VisitFunctionDecl(const FunctionDecl *D) {
     Out << '>';
   }
 
+  QualType CanonicalType = D->getType().getCanonicalType();
   // Mangle in type information for the arguments.
-  for (auto *PD : D->parameters()) {
-    Out << '#';
-    VisitType(PD->getType());
+  if (const auto *FPT = CanonicalType->getAs<FunctionProtoType>()) {
+    for (QualType PT : FPT->param_types()) {
+      Out << '#';
+      VisitType(PT);
+    }
   }
   if (D->isVariadic())
     Out << '.';

>From 909ae49f65155b1fd6a6e2718fc0746875c296ef Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Mon, 15 Apr 2024 16:33:44 -0400
Subject: [PATCH 2/2] [FOLD] add test

---
 clang/test/Index/USR/func-type.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/clang/test/Index/USR/func-type.cpp b/clang/test/Index/USR/func-type.cpp
index ff1cd37a7fc421..459a8cd6da5584 100644
--- a/clang/test/Index/USR/func-type.cpp
+++ b/clang/test/Index/USR/func-type.cpp
@@ -16,3 +16,15 @@ void Func( void (* (*)(int, int))(int, int) );
 // CHECK: {{[0-9]+}}:6 | function/C | Func | c:@F at Func#*F*Fv(#I#I)(#I#I)# |
 void Func( void (* (*)(int, int, int))(int) );
 // CHECK: {{[0-9]+}}:6 | function/C | Func | c:@F at Func#*F*Fv(#I)(#I#I#I)# |
+
+// Functions with parameter types that only differ in top-level cv-qualification should generate the same USR.
+
+void f( const int );
+// CHECK: {{[0-9]+}}:6 | function/C | f | c:@F at f#I# |
+void f( int );
+// CHECK: {{[0-9]+}}:6 | function/C | f | c:@F at f#I# |
+
+void g( int );
+// CHECK: {{[0-9]+}}:6 | function/C | g | c:@F at g#I# |
+void g( const int );
+// CHECK: {{[0-9]+}}:6 | function/C | g | c:@F at g#I# |