[clang] [clang][Sema] Don't emit 'declared here' note for builtin functions with no decl in source (PR #93394)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Youngsuk Kim (JOE1994)

<details>
<summary>Changes</summary>

Fixes #<!-- -->93369

---
Full diff: https://github.com/llvm/llvm-project/pull/93394.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaLookup.cpp (+10) 
- (modified) clang/test/SemaCXX/invalid-if-constexpr.cpp (+1-1) 


``````````diff
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index ef0a655b631ab..348f9e5b8f530 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -5897,6 +5897,16 @@ void Sema::diagnoseTypo(const TypoCorrection &Correction,
 
   NamedDecl *ChosenDecl =
       Correction.isKeyword() ? nullptr : Correction.getFoundDecl();
+
+  // For builtin functions which aren't declared anywhere in source,
+  // don't emit the "declared here" note.
+  if (auto *FD = dyn_cast_or_null<FunctionDecl>(ChosenDecl);
+      FD && FD->getBuiltinID() &&
+      PrevNote.getDiagID() == diag::note_previous_decl &&
+      Correction.getCorrectionRange().getBegin() == FD->getBeginLoc()) {
+    ChosenDecl = nullptr;
+  }
+
   if (PrevNote.getDiagID() && ChosenDecl)
     Diag(ChosenDecl->getLocation(), PrevNote)
       << CorrectedQuotedStr << (ErrorRecovery ? FixItHint() : FixTypo);
diff --git a/clang/test/SemaCXX/invalid-if-constexpr.cpp b/clang/test/SemaCXX/invalid-if-constexpr.cpp
index 7643c47488f05..16d422880e8a9 100644
--- a/clang/test/SemaCXX/invalid-if-constexpr.cpp
+++ b/clang/test/SemaCXX/invalid-if-constexpr.cpp
@@ -5,7 +5,7 @@ void similar() { // expected-note {{'similar' declared here}}
   if constexpr (similer<>) {} // expected-error {{use of undeclared identifier 'similer'; did you mean 'similar'?}}
 }
 void a() { if constexpr (__adl_swap<>) {}} // expected-error{{use of undeclared identifier '__adl_swap'; did you mean '__sync_swap'?}} \
-                                           // expected-note {{'__sync_swap' declared here}}
+                                           // not-expected-note {{'__sync_swap' declared here}}
 
 int AA() { return true;} // expected-note {{'AA' declared here}}
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/93394