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 {
}
_ => 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)
}
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())
}
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),
};
--- /dev/null
+// 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.
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub struct Foo {
+}
+
+impl Foo {
+ fn get(&self) -> Option<&Result<String, String>> {
+ None
+ }
+
+ fn mutate(&mut self) { }
+}
+
+fn main() {
+ let mut foo = Foo { };
+
+ // foo.get() returns type Option<&Result<String, String>>, so
+ // using `string` keeps borrow of `foo` alive. Hence calling
+ // `foo.mutate()` should be an error.
+ while let Some(Ok(string)) = foo.get() {
+ foo.mutate();
+ //~^ ERROR cannot borrow `foo` as mutable
+ println!("foo={:?}", *string);
+ }
+}