bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Add a nicer error message for missing in for loop, fixes #40782.

Browse source
This commit is contained in:
laurent 2017-10-30 22:33:57 +00:00
parent f0fe716dbc
commit 6a62ea6828
3 changed files with 74 additions and 6 deletions
Download patch file Download diff file Expand all files Collapse all files

54
src/libsyntax/parse/parser.rs
View file

@ -3154,13 +3154,55 @@ impl<'a> Parser<'a> {
// Parse: `for <src_pat> in <src_expr> <src_loop_block>`
let pat = self.parse_pat()?;
self.expect_keyword(keywords::In)?;
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
// Save the state of the parser before parsing 'in'.
let parser_snapshot_before_in = self.clone();
match self.expect_keyword(keywords::In) {
Ok(()) => {
let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs);
let hi = self.prev_span;
Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_ident), attrs))
let hi = self.prev_span;
Ok(self.mk_expr(
span_lo.to(hi),
ExprKind::ForLoop(pat, expr, loop_block, opt_ident),
attrs))
}
Err(mut in_err) => {
let parser_snapshot_after_in = self.clone();
// Rewind to before attempting to parse the 'in'.
mem::replace(self, parser_snapshot_before_in);
match self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None) {
Ok(expr) => {
// Successfully parsed the expr, print a nice error message.
in_err.cancel();
let in_span = parser_snapshot_after_in.span;
let mut err = self.sess.span_diagnostic
.struct_span_err(in_span, "missing `in` in `for` loop");
err.span_label(in_span, "expected `in` here");
let sugg = pprust::to_string(|s| {
s.s.word("for ")?;
s.print_pat(&pat)?;
s.s.word(" in ")?;
s.print_expr(&expr)
});
err.span_suggestion(
in_span,
"try adding `in`",
sugg);
Err(err)
}
Err(mut expr_err) => {
// Couldn't parse as an expr, return original error and parser state.
expr_err.cancel();
mem::replace(self, parser_snapshot_after_in);
Err(in_err)
}
}
}
}
}
/// Parse a 'while' or 'while let' expression ('while' token already eaten)