[Clang] Don't ditch typo-corrected lookup result

clang/docs/ReleaseNotes.rst

@@ -517,7 +517,10 @@ Improvements to Clang's diagnostics
 
 - Improved the ``-Wtautological-overlap-compare`` diagnostics to warn about overlapping and non-overlapping ranges involving character literals and floating-point literals. 
   The warning message for non-overlapping cases has also been improved (#GH13473).
-
+
+- Fixed a duplicate diagnostic when performing typo correction on function template
+  calls with explicit template arguments. (#GH139226)
+
 Improvements to Clang's time-trace
 ----------------------------------
 

clang/lib/Sema/SemaTemplate.cpp

@@ -523,6 +523,9 @@ bool Sema::LookupTemplateName(LookupResult &Found, Scope *S, CXXScopeSpec &SS,
       if (Found.isAmbiguous()) {
         Found.clear();
       } else if (!Found.empty()) {
+        // Do not erase the typo-corrected result to avoid duplicated
+        // diagnostics.
+        AllowFunctionTemplatesInLookup = true;
         Found.setLookupName(Corrected.getCorrection());
         if (LookupCtx) {
           std::string CorrectedStr(Corrected.getAsString(getLangOpts()));

clang/test/CXX/basic/basic.lookup/basic.lookup.classref/p1.cpp

@@ -98,3 +98,16 @@ namespace PR11856 {
     }
   }
 }
+
+namespace GH139226 {
+
+struct Foo {
+  template <class T> void LookupWithID(); // expected-note {{declared here}}
+};
+
+void test(Foo &f) {
+  f.LookupWithId<int>();
+  // expected-error@-1 {{did you mean 'LookupWithID'}}
+}
+
+}