[clang][CodeCompletion] Allow debuggers to code-complete reserved identifiers (llvm#84891)

(cherry picked from commit beb47e7)

Author: Michael137

clang/lib/Sema/SemaCodeComplete.cpp

@@ -700,6 +700,10 @@ ResultBuilder::ShadowMapEntry::end() const {
 // Filter out names reserved for the implementation if they come from a
 // system header.
 static bool shouldIgnoreDueToReservedName(const NamedDecl *ND, Sema &SemaRef) {
+  // Debuggers want access to all identifiers, including reserved ones.
+  if (SemaRef.getLangOpts().DebuggerSupport)
+    return false;
+
   ReservedIdentifierStatus Status = ND->isReserved(SemaRef.getLangOpts());
   // Ignore reserved names for compiler provided decls.
   if (isReservedInAllContexts(Status) && ND->getLocation().isInvalid())

clang/test/CodeCompletion/ordinary-name.c

@@ -5,6 +5,7 @@ typedef struct t _TYPEDEF;
 void foo() {
   int y;
   // RUN: %clang_cc1 -isystem %S/Inputs -fsyntax-only -code-completion-at=%s:%(line-1):9 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
+  // CHECK-CC1-NOT: __builtin_va_list
   // CHECK-CC1-NOT: __INTEGER_TYPE
   // CHECK-CC1: _Imaginary
   // CHECK-CC1: _MyPrivateType
@@ -15,4 +16,8 @@ void foo() {
   // CHECK-CC1: y
 
   // PR8744
-  // RUN: %clang_cc1 -isystem %S/Inputs -fsyntax-only -code-completion-at=%s:%(line-17):11 %s
+  // RUN: %clang_cc1 -isystem %S/Inputs -fsyntax-only -code-completion-at=%s:%(line-18):11 %s
+  
+  // RUN: %clang_cc1 -isystem %S/Inputs -fsyntax-only -fdebugger-support -code-completion-at=%s:%(line-15):9 %s -o - | FileCheck -check-prefix=CHECK-DBG %s
+  // CHECK-DBG: __builtin_va_list
+  // CHECK-DBG: __INTEGER_TYPE