Add structopt dependency in version 0.3.7

This patch series replaces argparse with structopt in the argument
handling code. As a first step, we need structopt as a dependency.

Import subrepo structopt/:structopt at efbdda4753592e27bc430fb01f7b9650b2f3174d
Import subrepo bitflags/:bitflags at 30668016aca6bd3b02c766e8347e0b4080d4c296
Import subrepo clap/:clap at 784524f7eb193e35f81082cc69454c8c21b948f7
Import subrepo heck/:heck at 093d56fbf001e1506e56dbfa38631d99b1066df1
Import subrepo proc-macro-error/:proc-macro-error at 6c4cfe79a622c5de8ae68557993542be46eacae2
Import subrepo proc-macro2/:proc-macro2 at d5d48eddca4566e5438e8a2cbed4a74e049544de
Import subrepo quote/:quote at 727436c6c137b20f0f34dde5d8fda2679b9747ad
Import subrepo rustversion/:rustversion at 0c5663313516263059ce9059ef81fc7a1cf655ca
Import subrepo syn-mid/:syn-mid at 5d3d85414a9e6674e1857ec22a87b96e04a6851a
Import subrepo syn/:syn at e87c27e87f6f4ef8919d0372bdb056d53ef0d8f3
Import subrepo textwrap/:textwrap at abcd618beae3f74841032aa5b53c1086b0a57ca2
Import subrepo unicode-segmentation/:unicode-segmentation at 637c9874c4fe0c205ff27787faf150a40295c6c3
Import subrepo unicode-width/:unicode-width at 3033826f8bf05e82724140a981d5941e48fce393
Import subrepo unicode-xid/:unicode-xid at 4baae9fffb156ba229665b972a9cd5991787ceb7

1 files changed, 136 insertions, 0 deletions

diff --git a/proc-macro-error/proc-macro-error/src/dummy.rs b/proc-macro-error/proc-macro-error/src/dummy.rs
new file mode 100644
index 0000000..f7443b3
--- /dev/null
+++ b/proc-macro-error/proc-macro-error/src/dummy.rs
@@ -0,0 +1,136 @@
+//! Facility to emit dummy implementations (or whatever) in case
+//! an error happen.
+//!
+//! `compile_error!` does not abort a compilation right away. This means
+//! `rustc` doesn't just show you the error and abort, it carries on the
+//! compilation process looking for other errors to report.
+//!
+//! Let's consider an example:
+//!
+//! ```rust,ignore
+//! use proc_macro::TokenStream;
+//! use proc_macro_error::*;
+//!
+//! trait MyTrait {
+//!     fn do_thing();
+//! }
+//!
+//! // this proc macro is supposed to generate MyTrait impl
+//! #[proc_macro_derive(MyTrait)]
+//! #[proc_macro_error]
+//! fn example(input: TokenStream) -> TokenStream {
+//!     // somewhere deep inside
+//!     abort!(span, "something's wrong");
+//!
+//!     // this implementation will be generated if no error happened
+//!     quote! {
+//!         impl MyTrait for #name {
+//!             fn do_thing() {/* whatever */}
+//!         }
+//!     }
+//! }
+//!
+//! // ================
+//! // in main.rs
+//!
+//! // this derive triggers an error
+//! #[derive(MyTrait)] // first BOOM!
+//! struct Foo;
+//!
+//! fn main() {
+//!     Foo::do_thing(); // second BOOM!
+//! }
+//! ```
+//!
+//! The problem is: the generated token stream contains only `compile_error!`
+//! invocation, the impl was not generated. That means user will see two compilation
+//! errors:
+//!
+//! ```text
+//! error: something's wrong
+//!  --> $DIR/probe.rs:9:10
+//!   |
+//! 9 |#[proc_macro_derive(MyTrait)]
+//!   |                    ^^^^^^^
+//!
+//! error[E0599]: no function or associated item named `do_thing` found for type `Foo` in the current scope
+//!  --> src\main.rs:3:10
+//!   |
+//! 1 | struct Foo;
+//!   | ----------- function or associated item `do_thing` not found for this
+//! 2 | fn main() {
+//! 3 |     Foo::do_thing(); // second BOOM!
+//!   |          ^^^^^^^^ function or associated item not found in `Foo`
+//! ```
+//!
+//! But the second error is meaningless! We definitely need to fix this.
+//!
+//! Most used approach in cases like this is "dummy implementation" -
+//! omit `impl MyTrait for #name` and fill functions bodies with `unimplemented!()`.
+//!
+//! This is how you do it:
+//!
+//! ```rust,ignore
+//! use proc_macro::TokenStream;
+//! use proc_macro_error::*;
+//!
+//!  trait MyTrait {
+//!      fn do_thing();
+//!  }
+//!
+//!  // this proc macro is supposed to generate MyTrait impl
+//!  #[proc_macro_derive(MyTrait)]
+//!  #[proc_macro_error]
+//!  fn example(input: TokenStream) -> TokenStream {
+//!      // first of all - we set a dummy impl which will be appended to
+//!      // `compile_error!` invocations in case a trigger does happen
+//!      set_dummy(quote! {
+//!          impl MyTrait for #name {
+//!              fn do_thing() { unimplemented!() }
+//!          }
+//!      });
+//!
+//!      // somewhere deep inside
+//!      abort!(span, "something's wrong");
+//!
+//!      // this implementation will be generated if no error happened
+//!      quote! {
+//!          impl MyTrait for #name {
+//!              fn do_thing() {/* whatever */}
+//!          }
+//!      }
+//!  }
+//!
+//!  // ================
+//!  // in main.rs
+//!
+//!  // this derive triggers an error
+//!  #[derive(MyTrait)] // first BOOM!
+//!  struct Foo;
+//!
+//!  fn main() {
+//!      Foo::do_thing(); // no more errors!
+//!  }
+//! ```
+
+use proc_macro2::TokenStream;
+use std::cell::Cell;
+
+use crate::check_correctness;
+
+thread_local! {
+    static DUMMY_IMPL: Cell<Option<TokenStream>> = Cell::new(None);
+}
+
+/// Sets dummy token stream which will be appended to `compile_error!(msg);...`
+/// invocations in case you'll emit any errors.
+///
+/// See [guide](../index.html#guide).
+pub fn set_dummy(dummy: TokenStream) -> Option<TokenStream> {
+    check_correctness();
+    DUMMY_IMPL.with(|old_dummy| old_dummy.replace(Some(dummy)))
+}
+
+pub(crate) fn cleanup() -> Option<TokenStream> {
+    DUMMY_IMPL.with(|old_dummy| old_dummy.replace(None))
+}