[clang][Sema] Improve diagnostics for function-like macros and update related notes

Author: StarOne01

clang/docs/ReleaseNotes.rst

@@ -128,8 +128,9 @@ Improvements to Clang's diagnostics
   which are supposed to only exist once per program, but may get duplicated when
   built into a shared library.
 - Fixed a bug where Clang's Analysis did not correctly model the destructor behavior of ``union`` members (#GH119415).
-- Clang now provides a diagnostic note for ``function-like macros`` that are missing the required parentheses.
-
+- Clang now provides a diagnostic note for function-like macros that are
+  missing the required parentheses (#GH123038).
+  
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -10857,8 +10857,8 @@ def err_undeclared_use_suggest : Error<
   "use of undeclared %0; did you mean %1?">;
 def err_undeclared_var_use_suggest : Error<
   "use of undeclared identifier %0; did you mean %1?">;
-def err_undeclared_var_use_suggest_func_like_macro
-    : Error<"use of undeclared identifier %0; did you mean %0(...)?">;
+def err_undeclared_var_use_suggest_func_like_macro : Error<
+  "%0 is defined as an object-like macro; did you mean '%0(...)'?">;
 def err_no_template : Error<"no template named %0">;
 def err_no_template_suggest : Error<"no template named %0; did you mean %1?">;
 def err_no_member_template : Error<"no template named %0 in %1">;

clang/lib/Sema/SemaExpr.cpp

@@ -2347,17 +2347,18 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
   return E;
 }
 
-// Check whether a similar function-like macro exists and suggest it
-static bool isFunctionLikeMacro(const DeclarationName &Name, Sema &SemaRef,
-                                const SourceLocation &TypoLoc) {
+// Diagnose when a macro cannot be expanded because it's a function-like macro
+// being used as an object-like macro. Returns true if a diagnostic is emitted.
+static bool diagnoseFunctionLikeMacro(Sema &SemaRef, DeclarationName Name,
+                                      SourceLocation TypoLoc) {
 
   if (IdentifierInfo *II = Name.getAsIdentifierInfo()) {
     if (II->hasMacroDefinition()) {
       MacroInfo *MI = SemaRef.PP.getMacroInfo(II);
       if (MI && MI->isFunctionLike()) {
         SemaRef.Diag(TypoLoc,
                      diag::err_undeclared_var_use_suggest_func_like_macro)
-            << II->getName();
+            << II;
         SemaRef.Diag(MI->getDefinitionLoc(),
                      diag::note_function_like_macro_requires_parens)
             << II->getName();
@@ -2403,11 +2404,10 @@ static void emitEmptyLookupTypoDiagnostic(
     if (Ctx)
       SemaRef.Diag(TypoLoc, diag::err_no_member) << Typo << Ctx
                                                  << SS.getRange();
-    else {
-      if (isFunctionLikeMacro(Typo, SemaRef, TypoLoc))
-        return;
+    else if (diagnoseFunctionLikeMacro(SemaRef, Typo, TypoLoc))
+      return;
+    else
       SemaRef.Diag(TypoLoc, DiagnosticID) << Typo;
-    }
     return;
   }
 
@@ -2648,7 +2648,7 @@ bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
   }
   R.clear();
 
-  if (isFunctionLikeMacro(Name, SemaRef, R.getNameLoc()))
+  if (diagnoseFunctionLikeMacro(SemaRef, Name, R.getNameLoc()))
     return true;
 
   // Emit a special diagnostic for failed member lookups.