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| 1 | +// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT |
| 2 | +// file at the top-level directory of this distribution and at |
| 3 | +// http://rust-lang.org/COPYRIGHT. |
| 4 | +// |
| 5 | +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| 6 | +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| 7 | +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| 8 | +// option. This file may not be copied, modified, or distributed |
| 9 | +// except according to those terms. |
| 10 | + |
| 11 | +//! Verifies that const fn arguments are immutable by value bindings |
| 12 | +//! and the const fn body doesn't contain any statements |
| 13 | +
|
| 14 | +use rustc::session::Session; |
| 15 | + |
| 16 | +use syntax::ast; |
| 17 | +use syntax::visit::{self, Visitor, FnKind}; |
| 18 | +use syntax::codemap::Span; |
| 19 | + |
| 20 | +pub fn check_crate(sess: &Session, krate: &ast::Crate) { |
| 21 | + visit::walk_crate(&mut CheckConstFn{ sess: sess }, krate); |
| 22 | + sess.abort_if_errors(); |
| 23 | +} |
| 24 | + |
| 25 | +struct CheckConstFn<'a> { |
| 26 | + sess: &'a Session, |
| 27 | +} |
| 28 | + |
| 29 | +struct CheckBlock<'a> { |
| 30 | + sess: &'a Session, |
| 31 | + kind: &'static str, |
| 32 | +} |
| 33 | + |
| 34 | +impl<'a, 'v> Visitor<'v> for CheckBlock<'a> { |
| 35 | + fn visit_block(&mut self, block: &'v ast::Block) { |
| 36 | + check_block(&self.sess, block, self.kind); |
| 37 | + CheckConstFn{ sess: self.sess}.visit_block(block); |
| 38 | + } |
| 39 | + fn visit_expr(&mut self, e: &'v ast::Expr) { |
| 40 | + if let ast::ExprClosure(..) = e.node { |
| 41 | + CheckConstFn{ sess: self.sess}.visit_expr(e); |
| 42 | + } else { |
| 43 | + visit::walk_expr(self, e); |
| 44 | + } |
| 45 | + } |
| 46 | + fn visit_item(&mut self, _i: &'v ast::Item) { panic!("should be handled in CheckConstFn") } |
| 47 | + fn visit_fn(&mut self, |
| 48 | + _fk: FnKind<'v>, |
| 49 | + _fd: &'v ast::FnDecl, |
| 50 | + _b: &'v ast::Block, |
| 51 | + _s: Span, |
| 52 | + _fn_id: ast::NodeId) { panic!("should be handled in CheckConstFn") } |
| 53 | +} |
| 54 | + |
| 55 | +fn check_block(sess: &Session, b: &ast::Block, kind: &'static str) { |
| 56 | + // Check all statements in the block |
| 57 | + for stmt in &b.stmts { |
| 58 | + let span = match stmt.node { |
| 59 | + ast::StmtDecl(ref decl, _) => { |
| 60 | + match decl.node { |
| 61 | + ast::DeclLocal(_) => decl.span, |
| 62 | + |
| 63 | + // Item statements are allowed |
| 64 | + ast::DeclItem(_) => continue, |
| 65 | + } |
| 66 | + } |
| 67 | + ast::StmtExpr(ref expr, _) => expr.span, |
| 68 | + ast::StmtSemi(ref semi, _) => semi.span, |
| 69 | + ast::StmtMac(..) => unreachable!(), |
| 70 | + }; |
| 71 | + span_err!(sess, span, E0016, |
| 72 | + "blocks in {}s are limited to items and tail expressions", kind); |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +impl<'a, 'v> Visitor<'v> for CheckConstFn<'a> { |
| 77 | + fn visit_item(&mut self, i: &'v ast::Item) { |
| 78 | + visit::walk_item(self, i); |
| 79 | + match i.node { |
| 80 | + ast::ItemConst(_, ref e) => { |
| 81 | + CheckBlock{ sess: self.sess, kind: "constant"}.visit_expr(e) |
| 82 | + }, |
| 83 | + ast::ItemStatic(_, _, ref e) => { |
| 84 | + CheckBlock{ sess: self.sess, kind: "static"}.visit_expr(e) |
| 85 | + }, |
| 86 | + _ => {}, |
| 87 | + } |
| 88 | + } |
| 89 | + |
| 90 | + fn visit_fn(&mut self, |
| 91 | + fk: FnKind<'v>, |
| 92 | + fd: &'v ast::FnDecl, |
| 93 | + b: &'v ast::Block, |
| 94 | + s: Span, |
| 95 | + _fn_id: ast::NodeId) { |
| 96 | + visit::walk_fn(self, fk, fd, b, s); |
| 97 | + match fk { |
| 98 | + FnKind::ItemFn(_, _, _, ast::Constness::Const, _, _) => {}, |
| 99 | + FnKind::Method(_, m, _) if m.constness == ast::Constness::Const => {}, |
| 100 | + _ => return, |
| 101 | + } |
| 102 | + |
| 103 | + // Ensure the arguments are simple, not mutable/by-ref or patterns. |
| 104 | + for arg in &fd.inputs { |
| 105 | + match arg.pat.node { |
| 106 | + ast::PatWild => {} |
| 107 | + ast::PatIdent(ast::BindingMode::ByValue(ast::MutImmutable), _, None) => {} |
| 108 | + _ => { |
| 109 | + span_err!(self.sess, arg.pat.span, E0022, |
| 110 | + "arguments of constant functions can only \ |
| 111 | + be immutable by-value bindings"); |
| 112 | + } |
| 113 | + } |
| 114 | + } |
| 115 | + check_block(&self.sess, b, "const function"); |
| 116 | + } |
| 117 | +} |
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