[clangd] Fix false positive in local rename collision detetction

[kbobyrev]

Summary

Fixes https://github.com/clangd/clangd/issues/685

[kbobyrev]

Fix comment formatting in the test.

[hokein]

Thanks for the quick fix.

clang-tools-extra/clangd/refactor/Rename.cpp

427

I think using doesThisDeclarationHaveABody is a better fit, e.g. Foo(Foo& a) = default; is a definition, but no function body :)

[kbobyrev]

Resolve review comment.

clang-tools-extra/clangd/refactor/Rename.cpp

if (const auto *Result = CheckDeclStmt(
       return Result;
     return CheckCompoundStmt(EnclosingFor->getBody(), NewName);
   }
   if (const auto *EnclosingFunction = Parent->get<FunctionDecl>()) {
     // Check for conflicts with other arguments.
     for (const auto *Parameter : EnclosingFunction->parameters())
       if (Parameter != &RenamedDecl && Parameter->getName() == NewName)
         return Parameter;
+    // FIXME: We don't modify all references to function parameters when
+    // renaming from forward declaration now, so using a name colliding with
+    // something in the definition's body is a valid transformation.
+    if (!EnclosingFunction->doesThisDeclarationHaveABody())
+      return nullptr;
     return CheckCompoundStmt(EnclosingFunction->getBody(), NewName);
   }
 
   return nullptr;
 }
 
 // Lookup the declarations (if any) with the given Name in the context of
 // RenameDecl.

clang-tools-extra/clangd/unittests/RenameTests.cpp

Case Cases[] = {
       {R"cpp(
         void func(int Conflict) {
           bool V^ar;
         }
       )cpp",
        "conflict", !HeaderFile, nullptr, "Conflict"},
 
       {R"cpp(
+        void func(int Var);
+
         void func(int V^ar) {
           bool Conflict;
         }
       )cpp",
        "conflict", !HeaderFile, nullptr, "Conflict"},
 
+      {R"cpp(// No conflict: only forward declaration's argument is renamed.
+        void func(int [[V^ar]]);
+
+        void func(int Var) {
+          bool Conflict;
+        }
+      )cpp",
+       nullptr, !HeaderFile, nullptr, "Conflict"},
+
       {R"cpp(
         void func(int V^ar, int Conflict) {
         }
       )cpp",
        "conflict", !HeaderFile, nullptr, "Conflict"},
 
       {R"cpp(// Trying to rename into the same name, SameName == SameName.
         void func() {