AST: Add some handy assertions to GenericSignature

Author: slavapestov

lib/AST/ASTContext.cpp

@@ -3700,6 +3700,11 @@ GenericSignature *GenericSignature::get(ArrayRef<GenericTypeParamType *> params,
                                         bool isKnownCanonical) {
   assert(!params.empty());
 
+#ifndef NDEBUG
+  for (auto req : requirements)
+    assert(req.getFirstType()->isTypeParameter());
+#endif
+
   // Check for an existing generic signature.
   llvm::FoldingSetNodeID ID;
   GenericSignature::Profile(ID, params, requirements);

lib/AST/GenericSignature.cpp

@@ -487,5 +487,7 @@ CanType GenericSignature::getCanonicalTypeInContext(Type type, ModuleDecl &mod)
     }
   });
 
-  return type->getCanonicalType();
+  auto result = type->getCanonicalType();
+  assert(isCanonicalTypeInContext(result, mod));
+  return result;
 }