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only emit suggestion to move & if the inner pattern is a binding

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This commit is contained in:
Niko Matsakis 2017-01-10 14:45:30 -05:00
parent 563ecc1b1f
commit 59d7d4c80e
1 changed files with 18 additions and 7 deletions
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25
src/librustc_typeck/check/_match.rs
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@ -30,10 +30,14 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
self.check_pat_arg(pat, expected, false);
}
/// The `is_arg` argument indicates whether this pattern is the
/// *outermost* pattern in an argument (e.g., in `fn foo(&x:
/// &u32)`, it is true for the `&x` pattern but not `x`). This is
/// used to tailor error reporting.
pub fn check_pat_arg(&self, pat: &'gcx hir::Pat, expected: Ty<'tcx>, is_arg: bool) {
let tcx = self.tcx;
debug!("check_pat(pat={:?},expected={:?})", pat, expected);
debug!("check_pat(pat={:?},expected={:?},is_arg={})", pat, expected, is_arg);
let ty = match pat.node {
PatKind::Wild => {
@ -206,6 +210,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
// can, to avoid creating needless variables. This
// also helps with the bad interactions of the given
// hack detailed in (*) below.
debug!("check_pat_arg: expected={:?}", expected);
let (rptr_ty, inner_ty) = match expected.sty {
ty::TyRef(_, mt) if mt.mutbl == mutbl => {
(expected, mt.ty)
@ -216,15 +221,21 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
let mt = ty::TypeAndMut { ty: inner_ty, mutbl: mutbl };
let region = self.next_region_var(infer::PatternRegion(pat.span));
let rptr_ty = tcx.mk_ref(region, mt);
debug!("check_pat_arg: demanding {:?} = {:?}", expected, rptr_ty);
let err = self.demand_eqtype_diag(pat.span, expected, rptr_ty);
// Look for a case like `fn foo(&foo: u32)` and suggest
// `fn foo(foo: &u32)`
if let Some(mut err) = err {
if is_arg {
if let Ok(snippet) = self.sess().codemap()
.span_to_snippet(pat.span)
{
err.help(&format!("did you mean `{}: &{}`?",
&snippet[1..],
expected));
if let PatKind::Binding(..) = inner.node {
if let Ok(snippet) = self.sess().codemap()
.span_to_snippet(pat.span)
{
err.help(&format!("did you mean `{}: &{}`?",
&snippet[1..],
expected));
}
}
}
err.emit();