[clang][HeuristicResolver] Default argument heuristic for template template parameters #156404
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@llvm/pr-subscribers-clang Author: Nathan Ridge (HighCommander4) ChangesFixes clangd/clangd#2478 Full diff: https://github.com/llvm/llvm-project/pull/156404.diff 2 Files Affected:
diff --git a/clang/lib/Sema/HeuristicResolver.cpp b/clang/lib/Sema/HeuristicResolver.cpp
index 8b424610feeda..6bfd1db602d4e 100644
--- a/clang/lib/Sema/HeuristicResolver.cpp
+++ b/clang/lib/Sema/HeuristicResolver.cpp
@@ -260,6 +260,25 @@ QualType HeuristicResolverImpl::simplifyType(QualType Type, const Expr *E,
}
}
}
+
+ // Similarly, heuristically replace a template template parameter with its
+ // default argument if it has one.
+ if (const auto *TST =
+ dyn_cast_if_present<TemplateSpecializationType>(T.Type)) {
+ if (const auto *TTPD = dyn_cast_if_present<TemplateTemplateParmDecl>(
+ TST->getTemplateName().getAsTemplateDecl())) {
+ if (TTPD->hasDefaultArgument()) {
+ const auto &DefaultArg = TTPD->getDefaultArgument().getArgument();
+ if (DefaultArg.getKind() == TemplateArgument::Template) {
+ if (const auto *CTD = dyn_cast_if_present<ClassTemplateDecl>(
+ DefaultArg.getAsTemplate().getAsTemplateDecl())) {
+ return {Ctx.getCanonicalTagType(CTD->getTemplatedDecl())};
+ }
+ }
+ }
+ }
+ }
+
// Check if the expression refers to an explicit object parameter of
// templated type. If so, heuristically treat it as having the type of the
// enclosing class.
diff --git a/clang/unittests/Sema/HeuristicResolverTest.cpp b/clang/unittests/Sema/HeuristicResolverTest.cpp
index cdbb4fe7c7eda..a69605e9f7466 100644
--- a/clang/unittests/Sema/HeuristicResolverTest.cpp
+++ b/clang/unittests/Sema/HeuristicResolverTest.cpp
@@ -545,6 +545,24 @@ TEST(HeuristicResolver, MemberExpr_DefaultTemplateArgument_Recursive) {
cxxMethodDecl(hasName("foo")).bind("output"));
}
+TEST(HeuristicResolver, MemberExpr_DefaultTemplateTemplateArgument) {
+ std::string Code = R"cpp(
+ template <typename T>
+ struct vector {
+ void push_back(T);
+ };
+ template <typename Element, template <typename> class Container = vector>
+ void foo(Container<Element> c, Element e) {
+ c.push_back(e);
+ }
+ )cpp";
+ // Test resolution of "push_back" in "c.push_back(e)".
+ expectResolution(
+ Code, &HeuristicResolver::resolveMemberExpr,
+ cxxDependentScopeMemberExpr(hasMemberName("push_back")).bind("input"),
+ cxxMethodDecl(hasName("push_back")).bind("output"));
+}
+
TEST(HeuristicResolver, MemberExpr_ExplicitObjectParameter) {
std::string Code = R"cpp(
struct Foo {
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September 16, 2025 19:25
…mplate parameters Fixes clangd/clangd#2478
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(Rebased, no other changes) |
zyn0217
approved these changes
Sep 17, 2025
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/88/builds/16191 Here is the relevant piece of the build log for the reference |
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/72/builds/15117 Here is the relevant piece of the build log for the reference |
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Fixes clangd/clangd#2478