[NFC] Crash if we try to convert non-ObjC protocols.

This should be a non-functional change because we shouldn't be converting
protocols which aren't ObjC.

Author: varungandhi-apple

lib/AST/ClangTypeConverter.cpp

@@ -372,7 +372,7 @@ clang::QualType ClangTypeConverter::visitProtocolType(ProtocolType *type) {
   auto &clangCtx = ClangASTContext;
 
   if (!proto->isObjC())
-    return getClangIdType(ClangASTContext);
+    return clang::QualType();
 
   assert(!cast_or_null<clang::ObjCProtocolDecl>(proto->getClangDecl())
          && "We shouldn't be creating duplicate decls; see `convert`");
@@ -416,6 +416,8 @@ clang::QualType ClangTypeConverter::visitClassType(ClassType *type) {
   auto &clangCtx = ClangASTContext;
   auto swiftDecl = type->getDecl();
 
+  // TODO: [non-objc-class-clang-type-conversion]
+  // See the corresponding note in GenClangType.cpp
   if (!swiftDecl->isObjC())
     return getClangIdType(clangCtx);
 

lib/IRGen/GenClangType.cpp

@@ -374,8 +374,13 @@ clang::CanQualType GenClangType::visitProtocolType(CanProtocolType type) {
   auto proto = type->getDecl();
   auto &clangCtx = getClangASTContext();
 
-  if (!proto->isObjC())
-    return getClangIdType(clangCtx);
+  if (!proto->isObjC()) {
+    std::string s;
+    llvm::raw_string_ostream err(s);
+    err << "Trying to compute the clang type for a non-ObjC protocol type\n";
+    proto->dump(err);
+    llvm::report_fatal_error(err.str());
+  }
 
   // Single protocol -> id<Proto>
   clang::IdentifierInfo *name = &clangCtx.Idents.get(proto->getName().get());
@@ -410,6 +415,9 @@ clang::CanQualType GenClangType::visitClassType(CanClassType type) {
   auto &clangCtx = getClangASTContext();
   auto swiftDecl = type->getDecl();
 
+  // TODO: [non-objc-class-clang-type-conversion]
+  // Crashing here instead of returning a bogus 'id' leads to test failures,
+  // which is surprising.
   if (!swiftDecl->isObjC())
     return getClangIdType(clangCtx);