bjoernager/rust
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Make break and continue hygienic

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Makes labelled loops hygiene by performing renaming of the labels
defined in e.g. `'x: loop { ... }` and then used in break and continue
statements within loop body so that they act hygienically when used with
macros.

Closes #12262.
This commit is contained in:
Edward Wang 2014-02-15 16:54:32 +08:00
parent 551da06157
commit 386db05df8
18 changed files with 262 additions and 28 deletions
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31
src/libsyntax/ext/expand.rs
View file

@ -139,6 +139,8 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
// Expand any interior macros etc.
// NB: we don't fold pats yet. Curious.
let src_expr = fld.fold_expr(src_expr).clone();
// Rename label before expansion.
let (opt_ident, src_loop_block) = rename_loop_label(opt_ident, src_loop_block, fld);
let src_loop_block = fld.fold_block(src_loop_block);
let span = e.span;
@ -165,8 +167,7 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
// `None => break ['<ident>];`
let none_arm = {
// FIXME #6993: this map goes away:
let break_expr = fld.cx.expr(span, ast::ExprBreak(opt_ident.map(|x| x.name)));
let break_expr = fld.cx.expr(span, ast::ExprBreak(opt_ident));
let none_pat = fld.cx.pat_ident(span, none_ident);
fld.cx.arm(span, ~[none_pat], break_expr)
};
@ -199,10 +200,36 @@ pub fn expand_expr(e: @ast::Expr, fld: &mut MacroExpander) -> @ast::Expr {
fld.cx.expr_match(span, discrim, ~[arm])
}
ast::ExprLoop(loop_block, opt_ident) => {
let (opt_ident, loop_block) =
rename_loop_label(opt_ident, loop_block, fld);
let loop_block = fld.fold_block(loop_block);
fld.cx.expr(e.span, ast::ExprLoop(loop_block, opt_ident))
}
_ => noop_fold_expr(e, fld)
}
}
// Rename loop label and its all occurrences inside the loop body
fn rename_loop_label(opt_ident: Option<Ident>,
loop_block: P<Block>,
fld: &mut MacroExpander) -> (Option<Ident>, P<Block>) {
match opt_ident {
Some(label) => {
// Generate fresh label and add to the existing pending renames
let new_label = fresh_name(&label);
let rename = (label, new_label);
fld.extsbox.info().pending_renames.push(rename);
let mut pending_renames = ~[rename];
let mut rename_fld = renames_to_fold(&mut pending_renames);
(Some(rename_fld.fold_ident(label)),
rename_fld.fold_block(loop_block))
}
None => (None, loop_block)
}
}
// eval $e with a new exts frame:
macro_rules! with_exts_frame (
($extsboxexpr:expr,$macros_escape:expr,$e:expr) =>