f66a3f7bba
MacEager is a MacResult implementation for the common case where you've already built each form of AST that you might return. Fixes #17637. Based on #18814. This is a [breaking-change] for syntax extensions: * MacExpr::new becomes MacEager::expr. * MacPat::new becomes MacEager::pat. * MacItems::new becomes MacEager::items. It takes a SmallVector directly, not an iterator.
39 lines
1.3 KiB
Rust
39 lines
1.3 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/// The compiler code necessary to support the cfg! extension, which expands to
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/// a literal `true` or `false` based on whether the given cfg matches the
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/// current compilation environment.
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use ast;
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use codemap::Span;
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use ext::base::*;
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use ext::base;
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use ext::build::AstBuilder;
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use attr;
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use attr::*;
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use parse::attr::ParserAttr;
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use parse::token;
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pub fn expand_cfg<'cx>(cx: &mut ExtCtxt,
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sp: Span,
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tts: &[ast::TokenTree])
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-> Box<base::MacResult+'static> {
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let mut p = cx.new_parser_from_tts(tts);
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let cfg = p.parse_meta_item();
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if !p.eat(&token::Eof) {
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cx.span_err(sp, "expected 1 cfg-pattern");
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return DummyResult::expr(sp);
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}
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let matches_cfg = attr::cfg_matches(&cx.parse_sess.span_diagnostic, &cx.cfg, &*cfg);
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MacEager::expr(cx.expr_bool(sp, matches_cfg))
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}
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