2017-03-30 23:08:33 -05:00
|
|
|
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
|
|
|
|
// file at the top-level directory of this distribution and at
|
|
|
|
// http://rust-lang.org/COPYRIGHT.
|
|
|
|
//
|
|
|
|
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
|
|
|
|
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
|
|
|
|
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
|
|
|
|
// option. This file may not be copied, modified, or distributed
|
|
|
|
// except according to those terms.
|
|
|
|
|
|
|
|
// no-prefer-dynamic
|
|
|
|
|
rustc: Tweak custom attribute capabilities
This commit starts to lay some groundwork for the stabilization of custom
attribute invocations and general procedural macros. It applies a number of
changes discussed on [internals] as well as a [recent issue][issue], namely:
* The path used to specify a custom attribute must be of length one and cannot
be a global path. This'll help future-proof us against any ambiguities and
give us more time to settle the precise syntax. In the meantime though a bare
identifier can be used and imported to invoke a custom attribute macro. A new
feature gate, `proc_macro_path_invoc`, was added to gate multi-segment paths
and absolute paths.
* The set of items which can be annotated by a custom procedural attribute has
been restricted. Statements, expressions, and modules are disallowed behind
two new feature gates: `proc_macro_expr` and `proc_macro_mod`.
* The input to procedural macro attributes has been restricted and adjusted.
Today an invocation like `#[foo(bar)]` will receive `(bar)` as the input token
stream, but after this PR it will only receive `bar` (the delimiters were
removed). Invocations like `#[foo]` are still allowed and will be invoked in
the same way as `#[foo()]`. This is a **breaking change** for all nightly
users as the syntax coming in to procedural macros will be tweaked slightly.
* Procedural macros (`foo!()` style) can only be expanded to item-like items by
default. A separate feature gate, `proc_macro_non_items`, is required to
expand to items like expressions, statements, etc.
Closes #50038
[internals]: https://internals.rust-lang.org/t/help-stabilize-a-subset-of-macros-2-0/7252
[issue]: https://github.com/rust-lang/rust/issues/50038
2018-04-20 09:50:39 -05:00
|
|
|
#![feature(proc_macro, proc_macro_non_items)]
|
2017-03-30 23:08:33 -05:00
|
|
|
#![crate_type = "proc-macro"]
|
|
|
|
|
|
|
|
extern crate proc_macro;
|
|
|
|
|
2018-04-02 10:19:32 -05:00
|
|
|
use proc_macro::{TokenStream, TokenTree, Spacing, Literal, quote};
|
2017-03-30 23:08:33 -05:00
|
|
|
|
|
|
|
#[proc_macro]
|
|
|
|
pub fn count_compound_ops(input: TokenStream) -> TokenStream {
|
|
|
|
assert_eq!(count_compound_ops_helper(quote!(++ (&&) 4@a)), 3);
|
2018-04-02 10:19:32 -05:00
|
|
|
let l = Literal::u32_suffixed(count_compound_ops_helper(input));
|
|
|
|
TokenTree::from(l).into()
|
2017-03-30 23:08:33 -05:00
|
|
|
}
|
|
|
|
|
|
|
|
fn count_compound_ops_helper(input: TokenStream) -> u32 {
|
|
|
|
let mut count = 0;
|
|
|
|
for token in input {
|
2018-04-02 10:19:32 -05:00
|
|
|
match &token {
|
|
|
|
TokenTree::Op(tt) if tt.spacing() == Spacing::Alone => {
|
|
|
|
count += 1;
|
|
|
|
}
|
|
|
|
TokenTree::Group(tt) => {
|
|
|
|
count += count_compound_ops_helper(tt.stream());
|
|
|
|
}
|
2017-03-30 23:08:33 -05:00
|
|
|
_ => {}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
count
|
|
|
|
}
|