Handle nested syn::Type:::Group

Currently, rustc does not pass the exact original TokenStream to
proc-macros in several cases. This has many undesirable effects, such as
losing correct location information in error message.
See rust-lang/rust#43081 for more details

In the future, rustc will begin passing the correct TokenStream to
proc-macros. As a result, `syn` may wrap a type in one or more
`syn::Type::Group`s (if the proc-macro input came from a `macro_rules!` expansion).

I've determined that this can cause `oauth1-request-derive` to fail to match
a `Type::Path`. This PR should properly handle nested groups, allowing
your crate to work with both old and new input.

If you have any questions, feel free to ask me. See rust-lang/rust#72622
for more details.

oauth1-request-derive/src/method_body.rs

@@ -47,7 +47,11 @@ impl<'a> ToTokens for MethodBody<'a> {
                 }
 
                 let ty_is_option = f.meta.option.get().map(|v| **v).unwrap_or_else(|| {
-                    if let Type::Path(ref ty_path) = f.ty {
+                    let mut ty = &f.ty;
+                    while let Type::Group(g) = ty {
+                        ty = &g.elem;
+                    }
+                    if let Type::Path(ref ty_path) = ty {
                         let path = &ty_path.path;
                         path.leading_colon.is_none()
                             && path.segments.len() == 1

oauth1-request-derive/tests/compile-fail/typeck.rs

@@ -2,13 +2,8 @@ use std::fmt::{self, Formatter};
 
 #[derive(oauth1_request_derive::Authorize)]
 //~^ ERROR: mismatched types
-//~| expected u8, found ()
-//~^^^ ERROR: mismatched types
-//~| expected (), found u8
-//~^^^^^ ERROR: `()` doesn't implement `std::fmt::Display`
-//~^^^^^^ ERROR: the trait bound `(): std::convert::AsRef<str>` is not satisfied
-//~^^^^^^^ ERROR: the trait bound `u8: std::convert::AsRef<str>` is not satisfied
-// FIXME: move these errors to (1) to (5) respectively
+//~| ERROR: `()` doesn't implement `std::fmt::Display` 
+//~| ERROR: mismatched types
 struct Test {
     not_display: (),
     //^ (3)
@@ -20,31 +15,26 @@ struct Test {
 
     #[oauth1(fmt = "fmt_arg_not_ref")]
     //~^ ERROR: mismatched types
-    //~| expected reference, found ()
     fmt_arg_not_ref: (),
 
     #[oauth1(fmt = "fmt_arg_mismatch")]
-    //^ (1)
     fmt_arg_mismatch: (),
 
     #[oauth1(fmt = "fmt_trait_bound_unsatisfied")]
-    //^ (4)
+    //~^ the trait bound `(): std::convert::AsRef<str>`
     fmt_trait_bound_unsatisfied: (),
 
     #[oauth1(fmt = "fmt_ret_mismatch")]
     //~^ ERROR: mismatched types
-    //~| expected struct `std::fmt::Error`, found ()
     fmt_ret_mismatch: (),
 
     #[oauth1(fmt = "NOT_FN")]
     //~^ ERROR: mismatched types
-    //~| expected fn pointer, found ()
     fmt_not_fn: (),
 
     #[oauth1(option = "true")]
     option_not_option: u8,
     //~^ ERROR: mismatched types
-    //~| expected enum `std::option::Option`, found u8
 
     #[oauth1(skip_if = "skip_if_too_many_args")]
     //~^ ERROR: mismatched types
@@ -53,25 +43,21 @@ struct Test {
 
     #[oauth1(skip_if = "skip_if_arg_not_ref")]
     //~^ ERROR: mismatched types
-    //~| expected reference, found u8
     skip_if_arg_not_ref: u8,
 
     #[oauth1(skip_if = "skip_if_arg_mismatch")]
-    //^ (2)
     skip_if_arg_mismatch: u8,
 
     #[oauth1(skip_if = "skip_if_trait_bound_unsatisfied")]
-    //- (5)
+    //~^ ERROR: the trait bound `u8: std::convert::AsRef<str>`
     skip_if_trait_bound_unsatisfied: u8,
 
     #[oauth1(skip_if = "skip_if_ret_mismatch")]
     //~^ ERROR: mismatched types
-    //~| expected bool, found enum `std::option::Option`
     skip_if_ret_mismatch: u8,
 
     #[oauth1(skip_if = "NOT_FN")]
     //~^ ERROR: mismatched types
-    //~| expected fn pointer, found ()
     skip_if_not_fn: u8,
 }