[C++20] [Modules] [Concepts] Recognize same concepts more precisely in Serialization

The compiler would judge two concepts is same by their addresses.
However, when we use modules, the addresses wouldn't be the same all the
time since one is parsed in their TU and another is imported in another
TU.
This patch fixes this by using isSameEntity to judge the two concepts.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D114769

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -2948,6 +2948,7 @@ uint64_t ASTReader::getGlobalBitOffset(ModuleFile &M, uint64_t LocalOffset) {
 static bool isSameTemplateParameterList(const ASTContext &C,
                                         const TemplateParameterList *X,
                                         const TemplateParameterList *Y);
+static bool isSameEntity(NamedDecl *X, NamedDecl *Y);
 
 /// Determine whether two template parameters are similar enough
 /// that they may be used in declarations of the same template.
@@ -2967,7 +2968,9 @@ static bool isSameTemplateParameter(const NamedDecl *X,
     if (!TXTC != !TYTC)
       return false;
     if (TXTC && TYTC) {
-      if (TXTC->getNamedConcept() != TYTC->getNamedConcept())
+      auto *NCX = TXTC->getNamedConcept();
+      auto *NCY = TYTC->getNamedConcept();
+      if (!NCX || !NCY || !isSameEntity(NCX, NCY))
         return false;
       if (TXTC->hasExplicitTemplateArgs() != TYTC->hasExplicitTemplateArgs())
         return false;
@@ -3111,11 +3114,12 @@ static bool hasSameOverloadableAttrs(const FunctionDecl *A,
 
 /// Determine whether the two declarations refer to the same entity.
 static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
-  assert(X->getDeclName() == Y->getDeclName() && "Declaration name mismatch!");
-
   if (X == Y)
     return true;
 
+  if (X->getDeclName() != Y->getDeclName())
+    return false;
+
   // Must be in the same context.
   //
   // Note that we can't use DeclContext::Equals here, because the DeclContexts

clang/test/Modules/Inputs/concept/A.cppm

@@ -0,0 +1,3 @@
+module;
+#include "foo.h"
+export module A;

clang/test/Modules/Inputs/concept/foo.h

@@ -0,0 +1,13 @@
+#ifndef FOO_H
+#define FOO_H
+
+template <class T>
+concept Range = requires(T &t) { t.begin(); };
+
+struct A {
+public:
+  template <Range T>
+  using range_type = T;
+};
+
+#endif

clang/test/Modules/concept.cppm

@@ -0,0 +1,10 @@
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: %clang -std=c++20 %S/Inputs/concept/A.cppm --precompile -o %t/A.pcm
+// RUN: %clang -std=c++20 -fprebuilt-module-path=%t -I%S/Inputs/concept %s -c -Xclang -verify
+// expected-no-diagnostics
+
+module;
+#include "foo.h"
+export module B;
+import A;