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, 254 insertions, 0 deletions

diff --git a/rustversion/src/lib.rs b/rustversion/src/lib.rs
new file mode 100644
index 0000000..cf8ed21
--- /dev/null
+++ b/rustversion/src/lib.rs
@@ -0,0 +1,254 @@
+//! This crate provides macros for conditional compilation according to rustc
+//! compiler version, analogous to [`#[cfg(...)]`][cfg] and
+//! [`#[cfg_attr(...)]`][cfg_attr].
+//!
+//! [cfg]: https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg-attribute
+//! [cfg_attr]: https://doc.rust-lang.org/reference/conditional-compilation.html#the-cfg_attr-attribute
+//!
+//! <br>
+//!
+//! # Selectors
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::stable]</code></b>
+//!   —<br>
+//!   True on any stable compiler.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::stable(1.34)]</code></b>
+//!   —<br>
+//!   True on exactly the specified stable compiler.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::beta]</code></b>
+//!   —<br>
+//!   True on any beta compiler.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::nightly]</code></b>
+//!   —<br>
+//!   True on any nightly compiler or dev build.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::nightly(2019-01-01)]</code></b>
+//!   —<br>
+//!   True on exactly one nightly.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::since(1.34)]</code></b>
+//!   —<br>
+//!   True on that stable release and any later compiler, including beta and
+//!   nightly.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::since(2019-01-01)]</code></b>
+//!   —<br>
+//!   True on that nightly and all newer ones.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::before(</code></b><i>version or date</i><b><code>)]</code></b>
+//!   —<br>
+//!   Negative of <i>#[rustversion::since(...)]</i>.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::not(</code></b><i>selector</i><b><code>)]</code></b>
+//!   —<br>
+//!   Negative of any selector; for example <i>#[rustversion::not(nightly)]</i>.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::any(</code></b><i>selectors...</i><b><code>)]</code></b>
+//!   —<br>
+//!   True if any of the comma-separated selectors is true; for example
+//!   <i>#[rustversion::any(stable, beta)]</i>.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::all(</code></b><i>selectors...</i><b><code>)]</code></b>
+//!   —<br>
+//!   True if all of the comma-separated selectors are true; for example
+//!   <i>#[rustversion::all(since(1.31), before(1.34))]</i>.
+//!   </p>
+//!
+//! - <p style="margin-left:50px;text-indent:-50px">
+//!   <b><code>#[rustversion::attr(</code></b><i>selector</i><b><code>, </code></b><i>attribute</i><b><code>)]</code></b>
+//!   —<br>
+//!   For conditional inclusion of attributes; analogous to
+//!   <code>cfg_attr</code>.
+//!   </p>
+//!
+//! <br>
+//!
+//! # Use cases
+//!
+//! Providing additional trait impls as types are stabilized in the standard library
+//! without breaking compatibility with older compilers; in this case Pin\<P\>
+//! stabilized in [Rust 1.33][pin]:
+//!
+//! [pin]: https://blog.rust-lang.org/2019/02/28/Rust-1.33.0.html#pinning
+//!
+//! ```
+//! # trait MyTrait {}
+//! #
+//! #[rustversion::since(1.33)]
+//! use std::pin::Pin;
+//!
+//! #[rustversion::since(1.33)]
+//! impl<P: MyTrait> MyTrait for Pin<P> {
+//!     /* ... */
+//! }
+//! ```
+//!
+//! Similar but for language features; the ability to control alignment greater than
+//! 1 of packed structs was stabilized in [Rust 1.33][packed].
+//!
+//! [packed]: https://github.com/rust-lang/rust/blob/master/RELEASES.md#version-1330-2019-02-28
+//!
+//! ```
+//! #[rustversion::attr(before(1.33), repr(packed))]
+//! #[rustversion::attr(since(1.33), repr(packed(2)))]
+//! struct Six(i16, i32);
+//!
+//! fn main() {
+//!     println!("{}", std::mem::align_of::<Six>());
+//! }
+//! ```
+//!
+//! Augmenting code with `const` as const impls are stabilized in the standard
+//! library. This use of `const` as an attribute is recognized as a special case
+//! by the rustversion::attr macro.
+//!
+//! ```
+//! use std::time::Duration;
+//!
+//! #[rustversion::attr(since(1.32), const)]
+//! fn duration_as_days(dur: Duration) -> u64 {
+//!     dur.as_secs() / 60 / 60 / 24
+//! }
+//! ```
+//!
+//! <br>
+
+extern crate proc_macro;
+
+mod attr;
+mod bound;
+mod date;
+mod expr;
+mod rustc;
+mod time;
+mod version;
+
+use crate::attr::Then;
+use crate::expr::Expr;
+use proc_macro::TokenStream;
+use proc_macro2::{Ident, Span, TokenStream as TokenStream2};
+use quote::quote;
+use syn::{parse_macro_input, ItemFn, Result};
+
+#[proc_macro_attribute]
+pub fn stable(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("stable", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn beta(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("beta", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn nightly(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("nightly", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn since(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("since", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn before(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("before", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn not(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("not", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn any(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("any", args, input)
+}
+
+#[proc_macro_attribute]
+pub fn all(args: TokenStream, input: TokenStream) -> TokenStream {
+    cfg("all", args, input)
+}
+
+fn cfg(top: &str, args: TokenStream, input: TokenStream) -> TokenStream {
+    match try_cfg(top, args, input) {
+        Ok(tokens) => tokens,
+        Err(err) => TokenStream::from(err.to_compile_error()),
+    }
+}
+
+fn try_cfg(top: &str, args: TokenStream, input: TokenStream) -> Result<TokenStream> {
+    let args = TokenStream2::from(args);
+    let top = Ident::new(top, Span::call_site());
+
+    let mut full_args = quote!(#top);
+    if !args.is_empty() {
+        full_args.extend(quote!((#args)));
+    }
+
+    let expr: Expr = syn::parse2(full_args)?;
+    let version = rustc::version()?;
+
+    if expr.eval(version) {
+        Ok(input)
+    } else {
+        Ok(TokenStream::new())
+    }
+}
+
+#[proc_macro_attribute]
+pub fn attr(args: TokenStream, input: TokenStream) -> TokenStream {
+    let args = parse_macro_input!(args as attr::Args);
+
+    match try_attr(args, input) {
+        Ok(tokens) => tokens,
+        Err(err) => TokenStream::from(err.to_compile_error()),
+    }
+}
+
+fn try_attr(args: attr::Args, input: TokenStream) -> Result<TokenStream> {
+    let version = rustc::version()?;
+
+    if !args.condition.eval(version) {
+        return Ok(input);
+    }
+
+    match args.then {
+        Then::Const(const_token) => {
+            let mut input: ItemFn = syn::parse(input)?;
+            input.sig.constness = Some(const_token);
+            Ok(TokenStream::from(quote!(#input)))
+        }
+        Then::Attribute(then) => {
+            let input = TokenStream2::from(input);
+            Ok(TokenStream::from(quote! {
+                #[cfg_attr(all(), #then)]
+                #input
+            }))
+        }
+    }
+}