diff options
| -rw-r--r-- | src/librustc_typeck/check/_match.rs | 35 | ||||
| -rw-r--r-- | src/libsyntax_pos/lib.rs | 12 | ||||
| -rw-r--r-- | src/test/ui/suggestions/dont-suggest-dereference-on-arg.rs | 18 | ||||
| -rw-r--r-- | src/test/ui/suggestions/dont-suggest-dereference-on-arg.stderr | 10 |
4 files changed, 66 insertions, 9 deletions
diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs index ea0fa945c37..fbfc97d33c5 100644 --- a/src/librustc_typeck/check/_match.rs +++ b/src/librustc_typeck/check/_match.rs @@ -23,7 +23,9 @@ use std::collections::hash_map::Entry::{Occupied, Vacant}; use std::cmp; use syntax::ast; use syntax::codemap::Spanned; +use syntax::errors::DiagnosticBuilder; use syntax::feature_gate; +use syntax::parse::ParseSess; use syntax::ptr::P; use syntax_pos::Span; @@ -120,17 +122,32 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> { .pat_adjustments_mut() .insert(pat.hir_id, pat_adjustments); } else { - let mut err = feature_gate::feature_err( - &tcx.sess.parse_sess, - "match_default_bindings", - pat.span, - feature_gate::GateIssue::Language, - "non-reference pattern used to match a reference", - ); + fn feature_err<'a>(sp: Span, sess: &'a ParseSess) -> DiagnosticBuilder<'a> { + feature_gate::feature_err( + sess, + "match_default_bindings", + sp, + feature_gate::GateIssue::Language, + "non-reference pattern used to match a reference", + ) + } if let Ok(snippet) = tcx.sess.codemap().span_to_snippet(pat.span) { - err.span_suggestion(pat.span, "consider using", format!("&{}", &snippet)); + // The following is a bit of a hack. We probably should check the AST for + // this instead, but this should be good enough for the expected cases. + let prev_span = pat.span.prev_point(); + let (sp, sugg) = match tcx.sess.codemap().span_to_snippet(prev_span) { + // Make the suggestion more obvious when having `&(_, _)` + Ok(ref prev) if &*prev == "&" => { + (prev_span.to(pat.span), format!("&&{}", &snippet)), + } + _ => (pat.span, format!("&{}", &snippet)), + }; + let mut err = feature_err(sp, &tcx.sess.parse_sess); + err.span_suggestion(sp, "consider using a reference", sugg); + err.emit(); + } else { + feature_err(pat.span, &tcx.sess.parse_sess).emit(); } - err.emit(); } } } diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs index 47755dc1d54..40a7917613f 100644 --- a/src/libsyntax_pos/lib.rs +++ b/src/libsyntax_pos/lib.rs @@ -159,6 +159,18 @@ impl Span { Span::new(BytePos(lo), BytePos(lo), span.ctxt) } + /// Returns a new span representing the previous character after the start-point of this span + pub fn prev_point(self) -> Span { + let span = self.data(); + let span_lo = span.lo.0; + let lo = if span_lo == 0 { + 0 + } else { + span_lo - 1 + }; + Span::new(BytePos(lo), BytePos(span_lo), span.ctxt) + } + /// Returns `self` if `self` is not the dummy span, and `other` otherwise. pub fn substitute_dummy(self, other: Span) -> Span { if self.source_equal(&DUMMY_SP) { other } else { self } diff --git a/src/test/ui/suggestions/dont-suggest-dereference-on-arg.rs b/src/test/ui/suggestions/dont-suggest-dereference-on-arg.rs new file mode 100644 index 00000000000..2a9ea464416 --- /dev/null +++ b/src/test/ui/suggestions/dont-suggest-dereference-on-arg.rs @@ -0,0 +1,18 @@ +// Copyright 2017 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +fn foo(s: &str) -> bool { true } + +fn main() { + let x = vec![(String::new(), String::new())]; + x.iter() + .filter(|&(ref a, _)| foo(a)) + .collect(); +} diff --git a/src/test/ui/suggestions/dont-suggest-dereference-on-arg.stderr b/src/test/ui/suggestions/dont-suggest-dereference-on-arg.stderr new file mode 100644 index 00000000000..fc1eb335d05 --- /dev/null +++ b/src/test/ui/suggestions/dont-suggest-dereference-on-arg.stderr @@ -0,0 +1,10 @@ +error: non-reference pattern used to match a reference (see issue #42640) + --> dont-suggest-dereference-on-arg.rs:16:19 + | +16 | .filter(|&(ref a, _)| foo(a)) + | ^^^^^^^^^^^ help: consider using: `&&(ref k, _)` + | + = help: add #![feature(match_default_bindings)] to the crate attributes to enable + +error: aborting due to previous error + |