src/librustc/middle/check_loop.rs

   1 // Copyright 2012 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
  12 use middle::ty;
  13
  14 use syntax::ast::*;
  15 use syntax::visit;
  16
  17 pub struct Context {
  18     in_loop: bool,
  19     can_ret: bool
  20 }
  21
  22 pub fn check_crate(tcx: ty::ctxt, crate: @crate) {
  23     visit::visit_crate(crate,
  24                        Context { in_loop: false, can_ret: true },
  25                        visit::mk_vt(@visit::Visitor {
  26         visit_item: |i, _cx, v| {
  27             visit::visit_item(i, Context {
  28                                     in_loop: false,
  29                                     can_ret: true
  30                                  }, v);
  31         },
  32         visit_expr: |e: @expr, cx: Context, v: visit::vt<Context>| {
  33             match e.node {
  34               expr_while(e, ref b) => {
  35                 (v.visit_expr)(e, cx, v);
  36                 (v.visit_block)(b, Context { in_loop: true,.. cx }, v);
  37               }
  38               expr_loop(ref b, _) => {
  39                 (v.visit_block)(b, Context { in_loop: true,.. cx }, v);
  40               }
  41               expr_fn_block(_, ref b) => {
  42                 (v.visit_block)(b, Context {
  43                                          in_loop: false,
  44                                          can_ret: false
  45                                       }, v);
  46               }
  47               expr_loop_body(@expr {node: expr_fn_block(_, ref b), _}) => {
  48                 let sigil = ty::ty_closure_sigil(ty::expr_ty(tcx, e));
  49                 let blk = (sigil == BorrowedSigil);
  50                 (v.visit_block)(b, Context {
  51                                          in_loop: true,
  52                                          can_ret: blk
  53                                      }, v);
  54               }
  55               expr_break(_) => {
  56                 if !cx.in_loop {
  57                     tcx.sess.span_err(e.span, "`break` outside of loop");
  58                 }
  59               }
  60               expr_again(_) => {
  61                 if !cx.in_loop {
  62                     tcx.sess.span_err(e.span, "`again` outside of loop");
  63                 }
  64               }
  65               expr_ret(oe) => {
  66                 if !cx.can_ret {
  67                     tcx.sess.span_err(e.span, "`return` in block function");
  68                 }
  69                 visit::visit_expr_opt(oe, cx, v);
  70               }
  71               _ => visit::visit_expr(e, cx, v)
  72             }
  73         },
  74         .. *visit::default_visitor()
  75     }));
  76 }