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Rollup merge of #32923 - jseyfried:fix_hygiene, r=nrc

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Fix macro hygiene bug

This fixes #32922 (EDIT: and fixes #31856), macro hygiene bugs.
It is a [breaking-change]. For example, the following would break:
```rust
fn main() {
    let x = true;
    macro_rules! foo { () => {
        let x = 0;
        macro_rules! bar { () => {x} }
        let _: bool = bar!();
        //^ `bar!()` used to resolve the first `x` (a bool),
        //| but will now resolve to the second x (an i32).
    }}
    foo! {};
}
```

r? @nrc
This commit is contained in:
Manish Goregaokar 2016-04-16 01:16:43 +05:30
commit 6a0cfbcac2
2 changed files with 50 additions and 8 deletions
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17
src/libsyntax/ext/expand.rs
View file

@ -504,6 +504,13 @@ pub fn expand_item_mac(it: P<ast::Item>,
/// Expand a stmt
fn expand_stmt(stmt: Stmt, fld: &mut MacroExpander) -> SmallVector<Stmt> {
// perform all pending renames
let stmt = {
let pending_renames = &mut fld.cx.syntax_env.info().pending_renames;
let mut rename_fld = IdentRenamer{renames:pending_renames};
rename_fld.fold_stmt(stmt).expect_one("rename_fold didn't return one value")
};
let (mac, style, attrs) = match stmt.node {
StmtKind::Mac(mac, style, attrs) => (mac, style, attrs),
_ => return expand_non_macro_stmt(stmt, fld)
@ -717,14 +724,8 @@ pub fn expand_block(blk: P<Block>, fld: &mut MacroExpander) -> P<Block> {
pub fn expand_block_elts(b: P<Block>, fld: &mut MacroExpander) -> P<Block> {
b.map(|Block {id, stmts, expr, rules, span}| {
let new_stmts = stmts.into_iter().flat_map(|x| {
// perform all pending renames
let renamed_stmt = {
let pending_renames = &mut fld.cx.syntax_env.info().pending_renames;
let mut rename_fld = IdentRenamer{renames:pending_renames};
rename_fld.fold_stmt(x).expect_one("rename_fold didn't return one value")
};
// expand macros in the statement
fld.fold_stmt(renamed_stmt).into_iter()
// perform pending renames and expand macros in the statement
fld.fold_stmt(x).into_iter()
}).collect();
let new_expr = expr.map(|x| {
let expr = {