[clang] [Sema] Add code completion for if constexpr and consteval (PR #124315)

[Younan Zhang via cfe-commits]

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@@ -6749,6 +6749,55 @@ void SemaCodeCompletion::CodeCompleteInitializer(Scope *S, Decl *D) {
   CodeCompleteExpression(S, Data);
 }
 
+void SemaCodeCompletion::CodeCompleteIfConst(Scope *S,
+                                             bool AfterExclaim) const {
+  ResultBuilder Results(SemaRef, CodeCompleter->getAllocator(),
+                        CodeCompleter->getCodeCompletionTUInfo(),
+                        CodeCompletionContext::CCC_Other);
+  CodeCompletionBuilder Builder(Results.getAllocator(),
+                                Results.getCodeCompletionTUInfo());
+  Results.EnterNewScope();
+  if (getLangOpts().CPlusPlus17) {
+    if (!AfterExclaim) {
+      if (Results.includeCodePatterns()) {
+        Builder.AddTypedTextChunk("constexpr");
+        Builder.AddChunk(CodeCompletionString::CK_HorizontalSpace);
+        Builder.AddChunk(CodeCompletionString::CK_LeftParen);
+        Builder.AddPlaceholderChunk("condition");
+        Builder.AddChunk(CodeCompletionString::CK_RightParen);
+        Builder.AddChunk(CodeCompletionString::CK_HorizontalSpace);
+        Builder.AddChunk(CodeCompletionString::CK_LeftBrace);
+        Builder.AddChunk(CodeCompletionString::CK_VerticalSpace);
+        Builder.AddPlaceholderChunk("statements");
+        Builder.AddChunk(CodeCompletionString::CK_VerticalSpace);
+        Builder.AddChunk(CodeCompletionString::CK_RightBrace);
+        Results.AddResult({Builder.TakeString()});
+      } else {
+        Results.AddResult({"constexpr"});
+      }
+    }
+  }
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zyn0217 wrote:

They should be tested

https://github.com/llvm/llvm-project/pull/124315