Fix TypeCheckAttr.cpp issues.
```
Failing Tests (7):
Swift(macosx-x86_64) :: AutoDiff/class_method_thunk/main.swift
Swift(macosx-x86_64) :: AutoDiff/differentiable_attr_cross_module/main.swift
Swift(macosx-x86_64) :: AutoDiff/differentiable_func_type_parse.swift
Swift(macosx-x86_64) :: AutoDiff/forward_mode_runtime.swift
Swift(macosx-x86_64) :: AutoDiff/generics.swift
Swift(macosx-x86_64) :: AutoDiff/linear_function_inst.sil
Swift(macosx-x86_64) :: AutoDiff/silgen_thunking/main.swift
```
