Address review comments

Author: hokein

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -5689,7 +5689,7 @@ def warn_func_template_missing : Warning<"instantiation of function %q0 "
 def note_forward_template_decl : Note<
   "forward declaration of template entity is here">;
 def note_unreachable_template_decl
-    : Note<"declaration of template entity is unreachable here">;
+    : Note<"unreachable declaration of template entity is here">;
 def note_inst_declaration_hint : Note<"add an explicit instantiation "
   "declaration to suppress this warning if %q0 is explicitly instantiated in "
   "another translation unit">;

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -5421,6 +5421,8 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
         Diag(PointOfInstantiation, diag::warn_func_template_missing)
             << Function;
         if (Unreachable) {
+          // FIXME: would be nice to mention which module the function template
+          // comes from. 
           Diag(PatternDecl->getLocation(),
                diag::note_unreachable_template_decl);
         } else {

clang/test/Modules/diag-undefined-template.cpp

@@ -1,7 +1,7 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -std=c++20 -fmodules -fmodules-cache-path=%t -I%S/Inputs/undefined-template \
 // RUN:   -Wundefined-func-template \
-// RUN:   -fimplicit-module-maps  %s 2>&1 | grep "declaration of template entity is unreachable here"
+// RUN:   -fimplicit-module-maps  %s 2>&1 | grep "unreachable declaration of template entity is her"
 
 #include "hoge.h"