[cxx-interop] Make sure to use the cannonical base class type.

Author: zoecarver

lib/IRGen/GenStruct.cpp

@@ -338,16 +338,18 @@ namespace {
 
       if (auto cxxRecord = dyn_cast<clang::CXXRecordDecl>(ClangDecl)) {
         for (auto base : cxxRecord->bases()) {
-          auto baseRecord = cast<clang::RecordType>(base.getType())->getDecl();
+          auto baseType = base.getType().getCanonicalType();
+
+          auto baseRecord = cast<clang::RecordType>(baseType)->getDecl();
           auto baseCxxRecord = cast<clang::CXXRecordDecl>(baseRecord);
 
           if (baseCxxRecord->isEmpty())
             continue;
 
           auto offset = layout.getBaseClassOffset(baseCxxRecord);
           auto size =
-              ClangDecl->getASTContext().getTypeSizeInChars(base.getType());
-          fn(base.getType(), offset, size);
+              ClangDecl->getASTContext().getTypeSizeInChars(baseType);
+          fn(baseType, offset, size);
         }
       }
     }

test/Interop/Cxx/class/inheritance/Inputs/fields.h

@@ -46,3 +46,12 @@ struct NonTrivialHasOneField {
 struct NonTrivialDerivedFromAll : NonTrivialHasOneField, NonTrivialDerivedWithOneField {
   int f = 6;
 };
+
+// Templates:
+
+template<class T>
+struct ClassTemplate {
+  T value;
+};
+
+struct DerivedFromClassTemplate : ClassTemplate<int> {};

test/Interop/Cxx/class/inheritance/fields.swift

@@ -52,4 +52,10 @@ FieldsTestSuite.test("Fields from derived from non trivial") {
   expectEqual(mutable.f, 48)
 }
 
+FieldsTestSuite.test("Derived from class template") {
+  var derived = DerivedFromClassTemplate()
+  derived.value = 42
+  expectEqual(derived.value, 42)
+}
+
 runAllTests()