[clang] print correct context for diagnostics suppressed by deduction

clang/docs/ReleaseNotes.rst

@@ -168,6 +168,8 @@ Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
 
 - Clang is now better at keeping track of friend function template instance contexts. (#GH55509)
+- Clang now prints the correct instantiation context for diagnostics suppressed
+  by template argument deduction.
 - The initialization kind of elements of structured bindings
   direct-list-initialized from an array is corrected to direct-initialization.
 
@@ -271,7 +273,7 @@ Code Completion
 Static Analyzer
 ---------------
 
-- Clang currently support extending lifetime of object bound to 
+- Clang currently support extending lifetime of object bound to
   reference members of aggregates in CFG and ExprEngine, that are
   created from default member initializer.
 

clang/include/clang/Sema/Sema.h

@@ -1908,7 +1908,23 @@ class Sema final : public SemaBase {
   /// '\#pragma clang attribute push' directives to the given declaration.
   void AddPragmaAttributes(Scope *S, Decl *D);
 
-  void PrintPragmaAttributeInstantiationPoint();
+  using InstantiationContextDiagFuncRef =
+      llvm::function_ref<void(SourceLocation, PartialDiagnostic)>;
+  auto getDefaultDiagFunc() {
+    return [this](SourceLocation Loc, PartialDiagnostic PD) {
+      // This bypasses a lot of the filters in the diag engine, as it's
+      // to be used to attach notes to diagnostics which have already
+      // been filtered through.
+      DiagnosticBuilder Builder(Diags.Report(Loc, PD.getDiagID()));
+      PD.Emit(Builder);
+    };
+  }
+
+  void PrintPragmaAttributeInstantiationPoint(
+      InstantiationContextDiagFuncRef DiagFunc);
+  void PrintPragmaAttributeInstantiationPoint() {
+    PrintPragmaAttributeInstantiationPoint(getDefaultDiagFunc());
+  }
 
   void DiagnoseUnterminatedPragmaAttribute();
 
@@ -13263,18 +13279,22 @@ class Sema final : public SemaBase {
   void pushCodeSynthesisContext(CodeSynthesisContext Ctx);
   void popCodeSynthesisContext();
 
-  void PrintContextStack() {
+  void PrintContextStack(InstantiationContextDiagFuncRef DiagFunc) {
     if (!CodeSynthesisContexts.empty() &&
         CodeSynthesisContexts.size() != LastEmittedCodeSynthesisContextDepth) {
-      PrintInstantiationStack();
+      PrintInstantiationStack(DiagFunc);
       LastEmittedCodeSynthesisContextDepth = CodeSynthesisContexts.size();
     }
     if (PragmaAttributeCurrentTargetDecl)
-      PrintPragmaAttributeInstantiationPoint();
+      PrintPragmaAttributeInstantiationPoint(DiagFunc);
   }
+  void PrintContextStack() { PrintContextStack(getDefaultDiagFunc()); }
   /// Prints the current instantiation stack through a series of
   /// notes.
-  void PrintInstantiationStack();
+  void PrintInstantiationStack(InstantiationContextDiagFuncRef DiagFunc);
+  void PrintInstantiationStack() {
+    PrintInstantiationStack(getDefaultDiagFunc());
+  }
 
   /// Determines whether we are currently in a context where
   /// template argument substitution failures are not considered

clang/lib/Sema/Sema.cpp

@@ -1655,11 +1655,20 @@ void Sema::EmitDiagnostic(unsigned DiagID, const DiagnosticBuilder &DB) {
     }
 
     case DiagnosticIDs::SFINAE_Suppress:
+      if (DiagnosticsEngine::Level Level = getDiagnostics().getDiagnosticLevel(
+              DiagInfo.getID(), DiagInfo.getLocation());
+          Level == DiagnosticsEngine::Ignored)
+        return;
       // Make a copy of this suppressed diagnostic and store it with the
       // template-deduction information;
       if (*Info) {
-        (*Info)->addSuppressedDiagnostic(DiagInfo.getLocation(),
-                       PartialDiagnostic(DiagInfo, Context.getDiagAllocator()));
+        (*Info)->addSuppressedDiagnostic(
+            DiagInfo.getLocation(),
+            PartialDiagnostic(DiagInfo, Context.getDiagAllocator()));
+        if (!Diags.getDiagnosticIDs()->isNote(DiagID))
+          PrintContextStack([Info](SourceLocation Loc, PartialDiagnostic PD) {
+            (*Info)->addSuppressedDiagnostic(Loc, std::move(PD));
+          });
       }
 
       // Suppress this diagnostic.

clang/lib/Sema/SemaAttr.cpp

@@ -1221,10 +1221,11 @@ void Sema::AddPragmaAttributes(Scope *S, Decl *D) {
   }
 }
 
-void Sema::PrintPragmaAttributeInstantiationPoint() {
+void Sema::PrintPragmaAttributeInstantiationPoint(
+    InstantiationContextDiagFuncRef DiagFunc) {
   assert(PragmaAttributeCurrentTargetDecl && "Expected an active declaration");
-  Diags.Report(PragmaAttributeCurrentTargetDecl->getBeginLoc(),
-               diag::note_pragma_attribute_applied_decl_here);
+  DiagFunc(PragmaAttributeCurrentTargetDecl->getBeginLoc(),
+           PDiag(diag::note_pragma_attribute_applied_decl_here));
 }
 
 void Sema::DiagnosePrecisionLossInComplexDivision() {

clang/lib/Sema/SemaExpr.cpp

@@ -225,9 +225,10 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
     // emit them now.
     auto Pos = SuppressedDiagnostics.find(D->getCanonicalDecl());
     if (Pos != SuppressedDiagnostics.end()) {
-      for (const PartialDiagnosticAt &Suppressed : Pos->second)
-        Diag(Suppressed.first, Suppressed.second);
-
+      for (const auto &[DiagLoc, PD] : Pos->second) {
+        DiagnosticBuilder Builder(Diags.Report(DiagLoc, PD.getDiagID()));
+        PD.Emit(Builder);
+      }
       // Clear out the list of suppressed diagnostics, so that we don't emit
       // them again for this specialization. However, we don't obsolete this
       // entry from the table, because we want to avoid ever emitting these