[clang] ItaniumMangle: fix mangling for unresolved types (llvm#135312)

Author: mizvekov

clang/lib/AST/ItaniumMangle.cpp

@@ -2511,7 +2511,6 @@ bool CXXNameMangler::mangleUnresolvedTypeOrSimpleId(QualType Ty,
   case Type::PackIndexing:
   case Type::TemplateTypeParm:
   case Type::UnaryTransform:
-  case Type::SubstTemplateTypeParm:
   unresolvedType:
     // Some callers want a prefix before the mangled type.
     Out << Prefix;
@@ -2524,6 +2523,16 @@ bool CXXNameMangler::mangleUnresolvedTypeOrSimpleId(QualType Ty,
     // so we return directly.
     return true;
 
+  case Type::SubstTemplateTypeParm: {
+    auto *ST = cast<SubstTemplateTypeParmType>(Ty);
+    // If this was replaced from a type alias, this is not substituted
+    // from an outer template parameter, so it's not an unresolved-type.
+    if (auto *TD = dyn_cast<TemplateDecl>(ST->getAssociatedDecl());
+        TD && TD->isTypeAlias())
+      return mangleUnresolvedTypeOrSimpleId(ST->getReplacementType(), Prefix);
+    goto unresolvedType;
+  }
+
   case Type::Typedef:
     mangleSourceNameWithAbiTags(cast<TypedefType>(Ty)->getDecl());
     break;

clang/test/CodeGenCXX/mangle.cpp

@@ -1220,3 +1220,30 @@ namespace test61 {
   // CHECK-LABEL: @_ZN6test611fINS_1XEEEvNT_1Y1aENS3_1bE
   template void f<X>(int, int);
 }
+
+namespace test62 {
+  template <class> struct integral_constant {
+    static const int value = true;
+  };
+  template <int> struct _OrImpl {};
+  template <class _Args> using _Or = _OrImpl<_Args::value>;
+  template <class _Up>
+  void f(_Or<integral_constant<_Up>>) {}
+  // CHECK-LABEL: @_ZN6test621fIiEEvNS_7_OrImplIXsr17integral_constantIT_EE5valueEEE
+  template void f<int>(_OrImpl<1>);
+} // namespace test62
+
+namespace test63 {
+  namespace {
+    template <class, class> struct integral_constant {
+      static const int value = true;
+    };
+    template <class, class> struct _And {};
+    template <int> struct _OrImpl {};
+    template <class _First> using _Or = _OrImpl<_First::value>;
+    template <class _Up>
+    void f(_And<integral_constant<int, void>, _Or<integral_constant<_Up, int>>>);
+  } // namespace
+  // CHECK-LABEL: @_ZN6test6312_GLOBAL__N_11fIiEEvNS0_4_AndINS0_17integral_constantIivEENS0_7_OrImplIXsr17integral_constantIT_iEE5valueEEEEE
+  void g() { f<int>({}); }
+} // namespace test63