Second try: Fix resolution and canonicalization of typedefs and function types

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
diff --git a/runtime/lib/mirrors.cc b/runtime/lib/mirrors.cc
index 7a2efe0bace42e415210bc1902508f09bcef972b..3cf5a681a256b5f19c7f33caab153806eb72d558 100644
--- a/runtime/lib/mirrors.cc
+++ b/runtime/lib/mirrors.cc
@@ -852,7 +852,7 @@ DEFINE_NATIVE_ENTRY(DeclarationMirror_metadata, 1) {
   if (decl.IsClass()) {
     klass ^= decl.raw();
     library = klass.library();
-  } else if (decl.IsFunction()) {
+  } else if (decl.IsFunction() && !Function::Cast(decl).IsSignatureFunction()) {
     klass = Function::Cast(decl).origin();
     library = klass.library();
   } else if (decl.IsField()) {