Thicken generic metatypes in BindGenericTypeParameters().

Generic metatypes should always be thick and TypeRef::subst() performs
the exact same transformation.

<rdar://problem/69765047>

Author: adrian-prantl

lldb/source/Target/SwiftLanguageRuntimeDynamicTypeResolution.cpp

@@ -1434,6 +1434,21 @@ SwiftLanguageRuntimeImpl::BindGenericTypeParameters(StackFrame &stack_frame,
           return type;
         });
 
+    // Thicken generic metatypes. Once substituted, they should always
+    // be thick. TypeRef::subst() does the same transformation.
+    target_swift_type =
+        target_swift_type.transform([](swift::Type type) -> swift::Type {
+          using namespace swift;
+          const auto thin = MetatypeRepresentation::Thin;
+          const auto thick = MetatypeRepresentation::Thick;
+          if (auto *metatype = dyn_cast<AnyMetatypeType>(type.getPointer()))
+            if (metatype->hasRepresentation() &&
+                metatype->getRepresentation() == thin &&
+                metatype->getInstanceType()->hasTypeParameter())
+              return MetatypeType::get(metatype->getInstanceType(), thick);
+          return type;
+        });
+
     while (target_swift_type->hasOpaqueArchetype()) {
       auto old_type = target_swift_type;
       target_swift_type = target_swift_type.subst(

lldb/test/API/lang/swift/expression/static/TestSwiftExpressionsInClassFunctions.py

@@ -76,5 +76,14 @@ def test_expressions_in_class_functions(self):
             self.check_expression("i", str(i), False)
             if i == 6:
               self.check_expression("self", "a.H<Int>")
+              frame = threads[0].GetFrameAtIndex(0)
+              lldbutil.check_variable(self, frame.FindVariable("self"),
+                                      use_dynamic=True,
+                                      # FIXME: This should be '@thick a.H<Swift.Int>.Type'
+                                      # but valobj.GetDynamicValue(lldb.eDynamicCanRunTarget)
+                                      # doesn't seem to do its job.
+                                      # rdar://problem/69889462
+                                      typename='@thin a.H<τ_0_0>.Type')
+
             self.runCmd("continue")