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make mem-categorization use adjusted type for patterns

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Fixes #49631
This commit is contained in:
Niko Matsakis 2018-04-05 17:16:07 -04:00
parent 5ee891cfea
commit 9428a3cea6
3 changed files with 80 additions and 4 deletions
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37
src/librustc/middle/mem_categorization.rs
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@ -503,8 +503,37 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
self.resolve_type_vars_or_error(expr.hir_id, self.tables.expr_ty_adjusted_opt(expr))
}
/// Returns the type of value that this pattern matches against.
/// Some non-obvious cases:
///
/// - a `ref x` binding matches against a value of type `T` and gives
/// `x` the type `&T`; we return `T`.
/// - a pattern with implicit derefs (thanks to default binding
/// modes #42640) may look like `Some(x)` but in fact have
/// implicit deref patterns attached (e.g., it is really
/// `&Some(x)`). In that case, we return the "outermost" type
/// (e.g., `&Option<T>).
fn pat_ty(&self, pat: &hir::Pat) -> McResult<Ty<'tcx>> {
// Check for implicit `&` types wrapping the pattern; note
// that these are never attached to binding patterns, so
// actually this is somewhat "disjoint" from the code below
// that aims to account for `ref x`.
if let Some(vec) = self.tables.pat_adjustments().get(pat.hir_id) {
if let Some(first_ty) = vec.first() {
debug!("pat_ty(pat={:?}) found adjusted ty `{:?}`", pat, first_ty);
return Ok(first_ty);
}
}
self.pat_ty_unadjusted(pat)
}
/// Like `pat_ty`, but ignores implicit `&` patterns.
fn pat_ty_unadjusted(&self, pat: &hir::Pat) -> McResult<Ty<'tcx>> {
let base_ty = self.node_ty(pat.hir_id)?;
debug!("pat_ty(pat={:?}) base_ty={:?}", pat, base_ty);
// This code detects whether we are looking at a `ref x`,
// and if so, figures out what the type *being borrowed* is.
let ret_ty = match pat.node {
@ -531,8 +560,8 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
}
_ => base_ty,
};
debug!("pat_ty(pat={:?}) base_ty={:?} ret_ty={:?}",
pat, base_ty, ret_ty);
debug!("pat_ty(pat={:?}) ret_ty={:?}", pat, ret_ty);
Ok(ret_ty)
}
@ -1246,7 +1275,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
self.tcx.adt_def(enum_def).variant_with_id(def_id).fields.len())
}
Def::StructCtor(_, CtorKind::Fn) => {
match self.pat_ty(&pat)?.sty {
match self.pat_ty_unadjusted(&pat)?.sty {
ty::TyAdt(adt_def, _) => {
(cmt, adt_def.non_enum_variant().fields.len())
}
@ -1297,7 +1326,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
PatKind::Tuple(ref subpats, ddpos) => {
// (p1, ..., pN)
let expected_len = match self.pat_ty(&pat)?.sty {
let expected_len = match self.pat_ty_unadjusted(&pat)?.sty {
ty::TyTuple(ref tys) => tys.len(),
ref ty => span_bug!(pat.span, "tuple pattern unexpected type {:?}", ty),
};