[clang][HeuristicResolver] Apply default argument heuristic in resolveDeclRefExpr as well

[HighCommander4]

This is a follow-up to #131074. After moving the default argument heuristic to simplifyType as per this discussion, I realized that this made it no longer apply to the DependentScopeDeclRefExpr case, because that wasn't using simplifyType.

This patch fixes that, with an added testcase.

[llvmbot]

@llvm/pr-subscribers-clangd
@llvm/pr-subscribers-clang-tools-extra

@llvm/pr-subscribers-clang

Author: Nathan Ridge (HighCommander4)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/132576.diff

3 Files Affected:

• (modified) clang-tools-extra/clangd/unittests/XRefsTests.cpp (+1-1)
• (modified) clang/lib/Sema/HeuristicResolver.cpp (+3-3)
• (modified) clang/unittests/Sema/HeuristicResolverTest.cpp (+17)

diff --git a/clang-tools-extra/clangd/unittests/XRefsTests.cpp b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
index e12d7691c58fb..693e965e78a96 100644
--- a/clang-tools-extra/clangd/unittests/XRefsTests.cpp
+++ b/clang-tools-extra/clangd/unittests/XRefsTests.cpp
@@ -1091,7 +1091,7 @@ TEST(LocateSymbol, All) {
       )objc",
       R"cpp(
         struct PointerIntPairInfo {
-          static void *getPointer(void *Value);
+          static void *$decl[[getPointer]](void *Value);
         };
 
         template <typename Info = PointerIntPairInfo> struct PointerIntPair {
diff --git a/clang/lib/Sema/HeuristicResolver.cpp b/clang/lib/Sema/HeuristicResolver.cpp
index d377379c627db..5f1495f5334b9 100644
--- a/clang/lib/Sema/HeuristicResolver.cpp
+++ b/clang/lib/Sema/HeuristicResolver.cpp
@@ -300,9 +300,9 @@ std::vector<const NamedDecl *> HeuristicResolverImpl::resolveMemberExpr(
 
 std::vector<const NamedDecl *>
 HeuristicResolverImpl::resolveDeclRefExpr(const DependentScopeDeclRefExpr *RE) {
-  return resolveDependentMember(
-      resolveNestedNameSpecifierToType(RE->getQualifier()), RE->getDeclName(),
-      StaticFilter);
+  QualType Qualifier = resolveNestedNameSpecifierToType(RE->getQualifier());
+  Qualifier = simplifyType(Qualifier, nullptr, /*UnwrapPointer=*/false);
+  return resolveDependentMember(Qualifier, RE->getDeclName(), StaticFilter);
 }
 
 std::vector<const NamedDecl *>
diff --git a/clang/unittests/Sema/HeuristicResolverTest.cpp b/clang/unittests/Sema/HeuristicResolverTest.cpp
index c7cfe7917c532..b4994c315b2ff 100644
--- a/clang/unittests/Sema/HeuristicResolverTest.cpp
+++ b/clang/unittests/Sema/HeuristicResolverTest.cpp
@@ -429,6 +429,23 @@ TEST(HeuristicResolver, DeclRefExpr_StaticMethod) {
       cxxMethodDecl(hasName("bar")).bind("output"));
 }
 
+TEST(HeuristicResolver, DeclRefExpr_DefaultTemplateArgument) {
+  std::string Code = R"cpp(
+    struct Default {
+      static void foo();
+    };
+    template <typename T = Default>
+    void bar() {
+      T::foo();
+    }
+  )cpp";
+  // Test resolution of "foo" in "T::foo()".
+  expectResolution(
+      Code, &HeuristicResolver::resolveDeclRefExpr,
+      dependentScopeDeclRefExpr(hasDependentName("foo")).bind("input"),
+      cxxMethodDecl(hasName("foo")).bind("output"));
+}
+
 TEST(HeuristicResolver, DeclRefExpr_StaticOverloads) {
   std::string Code = R"cpp(
     template <typename T>

[HighCommander4]

(Rebased)

[zyn0217]

Thanks for following up on it, this looks great.

Please flesh out the PR body before you commit, with the reason you said in #132576 (comment).
(Just a copy-paste is good enough)

[HighCommander4]

(I'm holding off on merging this until #130473 is merged first. There isn't an actual code dependency, it just simplifies the version control workflow to merge things in the order in which I have them stacked locally.)

[HighCommander4]

(Rebased)