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typeck: handle unsized structs in type hints by recursing into their last field. #27294

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Merged
merged 1 commit into from
Jul 27, 2015
Merged

typeck: handle unsized structs in type hints by recursing into their last field. #27294

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10 changes: 5 additions & 5 deletions src/librustc_typeck/check/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2490,7 +2490,7 @@ fn check_argument_types<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
// The special-cased logic below has three functions:
// 1. Provide as good of an expected type as possible.
let expected = expected_arg_tys.get(i).map(|&ty| {
Expectation::rvalue_hint(ty)
Expectation::rvalue_hint(fcx.tcx(), ty)
});

check_expr_with_unifier(fcx, &**arg,
Expand Down Expand Up @@ -3268,7 +3268,7 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
match unop {
ast::UnUniq => match ty.sty {
ty::TyBox(ty) => {
Expectation::rvalue_hint(ty)
Expectation::rvalue_hint(tcx, ty)
}
_ => {
NoExpectation
Expand Down Expand Up @@ -3345,7 +3345,7 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
// the last field of a struct can be unsized.
ExpectHasType(mt.ty)
} else {
Expectation::rvalue_hint(mt.ty)
Expectation::rvalue_hint(tcx, mt.ty)
}
}
_ => NoExpectation
Expand Down Expand Up @@ -3982,8 +3982,8 @@ impl<'tcx> Expectation<'tcx> {
/// which still is useful, because it informs integer literals and the like.
/// See the test case `test/run-pass/coerce-expect-unsized.rs` and #20169
/// for examples of where this comes up,.
fn rvalue_hint(ty: Ty<'tcx>) -> Expectation<'tcx> {
match ty.sty {
fn rvalue_hint(tcx: &ty::ctxt<'tcx>, ty: Ty<'tcx>) -> Expectation<'tcx> {
match tcx.struct_tail(ty).sty {
ty::TySlice(_) | ty::TyTrait(..) => {
ExpectRvalueLikeUnsized(ty)
}
Expand Down
5 changes: 5 additions & 0 deletions src/test/run-pass/coerce-expect-unsized.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,9 @@
#![allow(unknown_features)]
#![feature(box_syntax)]

use std::cell::RefCell;
use std::fmt::Debug;
use std::rc::Rc;

// Check that coercions apply at the pointer level and don't cause
// rvalue expressions to be unsized. See #20169 for more information.
Expand Down Expand Up @@ -45,6 +47,9 @@ pub fn main() {
let _: Box<[isize]> = Box::new([1, 2, 3]);
let _: Box<Fn(isize) -> _> = Box::new(|x| (x as u8));

let _: Rc<RefCell<[isize]>> = Rc::new(RefCell::new([1, 2, 3]));
let _: Rc<RefCell<FnMut(isize) -> _>> = Rc::new(RefCell::new(|x| (x as u8)));

let _: Vec<Box<Fn(isize) -> _>> = vec![
Box::new(|x| (x as u8)),
Box::new(|x| (x as i16 as u8)),
Expand Down