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

[zyn0217]

For a member function call like 'foo.bar()', there are two typo-correction points after parsing the dot. The first occurs in ParseOptionalCXXScopeSpecifier, which tries to annotate the template name following any scope specifiers.

If the template name bar is not found within 'foo', the parser was previously instructed to drop any function templates found outside of the scope. This was intended to prevent ambiguity in expressions like 'foo->bar < 7', as explained in commit 50a3cdd. However, it's unnecessary to discard typo-corrected results that were strictly resolved within the scope 'foo'.

We won't perform a second typo-correction in ParseUnqualifiedId after the name being annotated.

Fixes #139226

[llvmbot]

@llvm/pr-subscribers-clang

Author: Younan Zhang (zyn0217)

Changes

For a member function call like 'foo.bar<int>()', there are two typo-correction points after parsing the dot. The first occurs in ParseOptionalCXXScopeSpecifier, which tries to annotate the template name following any scope specifiers.

If the template name bar is not found within 'foo', the parser was previously instructed to drop any function templates found outside of the scope. This was intended to prevent ambiguity in expressions like 'foo->bar < 7', as explained in commit 50a3cdd. However, it's unnecessary to discard typo-corrected results that were strictly resolved within the scope 'foo'.

We won't perform a second typo-correction in ParseUnqualifiedId after the name being annotated.

Fixes #139226

---

Full diff: https://github.com/llvm/llvm-project/pull/139374.diff

3 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+4-1)
• (modified) clang/lib/Sema/SemaTemplate.cpp (+3)
• (modified) clang/test/CXX/basic/basic.lookup/basic.lookup.classref/p1.cpp (+13)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 1d0896f585fb4..234c28a143cf1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/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. Fixes #GH139226.
+
 Improvements to Clang's time-trace
 ----------------------------------
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 2ba69c87d95e3..a18b545a5feea 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/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 duplicating the typo
+        // correction in future.
+        AllowFunctionTemplatesInLookup = true;
         Found.setLookupName(Corrected.getCorrection());
         if (LookupCtx) {
           std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
diff --git a/clang/test/CXX/basic/basic.lookup/basic.lookup.classref/p1.cpp b/clang/test/CXX/basic/basic.lookup/basic.lookup.classref/p1.cpp
index e3599db18350b..3633ef1c293e2 100644
--- a/clang/test/CXX/basic/basic.lookup/basic.lookup.classref/p1.cpp
+++ b/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'}}
+}
+
+}

[cor3ntin]

Thanks