Merge pull request swiftlang#33709 from slavapestov/fix-opaque-type-decl-in-constrained-extension-5.3

ASTDemangler: Fix reconstruction of opaque result type defined in a constrained extension [5.3]

Author: tkremenek

lib/AST/ASTDemangler.cpp

@@ -200,21 +200,16 @@ createSubstitutionMapFromGenericArgs(GenericSignature genericSig,
   if (!genericSig)
     return SubstitutionMap();
 
-  SmallVector<GenericTypeParamType *, 4> genericParams;
-  genericSig->forEachParam([&](GenericTypeParamType *gp, bool canonical) {
-    if (canonical)
-      genericParams.push_back(gp);
-  });
-  if (genericParams.size() != args.size())
+  if (genericSig->getGenericParams().size() != args.size())
     return SubstitutionMap();
 
   return SubstitutionMap::get(
       genericSig,
       [&](SubstitutableType *t) -> Type {
-        for (unsigned i = 0, e = genericParams.size(); i < e; ++i) {
-          if (t->isEqual(genericParams[i]))
-            return args[i];
-        }
+        auto *gp = cast<GenericTypeParamType>(t);
+        unsigned ordinal = genericSig->getGenericParamOrdinal(gp);
+        if (ordinal < args.size())
+          return args[ordinal];
         return Type();
       },
       LookUpConformanceInModule(moduleDecl));

test/TypeDecoder/opaque_return_type.swift

@@ -12,6 +12,12 @@ var prop: some P { return 0 }
 
 func bar() -> some Sequence { return [] }
 
+struct G<T> {}
+
+extension G where T == Int {
+  var baz: some P { return 0 }
+}
+
 // DEMANGLE: $s18opaque_return_type3fooQryFQOyQo_
 // CHECK: some P
 
@@ -21,5 +27,8 @@ func bar() -> some Sequence { return [] }
 // DEMANGLE: $s18opaque_return_type3barQryFQOyQo_
 // CHECK: some Sequence
 
+// DEMANGLE: $s18opaque_return_type1GVAASiRszlE3bazQrvpQOySi_Qo_
+// CHECK: some P
+
 // DEMANGLE: $s18opaque_return_type3barQryFQOyQo_7ElementSTQxD
 // CHECK: (some Sequence).Element