Change error scheme so that if projection fails we generate `A::B` instead of `TyError`
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64b720229c
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@ -426,11 +426,25 @@ fn opt_normalize_projection_type<'a,'b,'tcx>(
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}
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}
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/// in various error cases, we just set TyError and return an obligation
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/// that, when fulfilled, will lead to an error.
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/// If we are projecting `<T as Trait>::Item`, but `T: Trait` does not
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/// hold. In various error cases, we cannot generate a valid
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/// normalized projection. Therefore, we create an inference variable
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/// return an associated obligation that, when fulfilled, will lead to
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/// an error.
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///
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/// FIXME: the TyError created here can enter the obligation we create,
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/// leading to error messages involving TyError.
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/// Note that we used to return `TyError` here, but that was quite
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/// dubious -- the premise was that an error would *eventually* be
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/// reported, when the obligation was processed. But in general once
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/// you see a `TyError` you are supposed to be able to assume that an
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/// error *has been* reported, so that you can take whatever heuristic
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/// paths you want to take. To make things worse, it was possible for
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/// cycles to arise, where you basically had a setup like `<MyType<$0>
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/// as Trait>::Foo == $0`. Here, normalizing `<MyType<$0> as
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/// Trait>::Foo> to `[type error]` would lead to an obligation of
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/// `<MyType<[type error]> as Trait>::Foo`. We are supposed to report
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/// an error for this obligation, but we legitimately should not,
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/// because it contains `[type error]`. Yuck! (See issue #29857 for
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/// one case where this arose.)
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fn normalize_to_error<'a,'tcx>(selcx: &mut SelectionContext<'a,'tcx>,
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projection_ty: ty::ProjectionTy<'tcx>,
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cause: ObligationCause<'tcx>,
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@ -441,8 +455,9 @@ fn normalize_to_error<'a,'tcx>(selcx: &mut SelectionContext<'a,'tcx>,
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let trait_obligation = Obligation { cause: cause,
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recursion_depth: depth,
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predicate: trait_ref.to_predicate() };
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let new_value = selcx.infcx().next_ty_var();
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Normalized {
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value: selcx.tcx().types.err,
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value: new_value,
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obligations: vec!(trait_obligation)
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}
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}
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@ -1038,6 +1038,9 @@ fn report_cast_to_unsized_type<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
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t_cast: Ty<'tcx>,
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t_expr: Ty<'tcx>,
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id: ast::NodeId) {
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if t_cast.references_error() || t_expr.references_error() {
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return;
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}
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let tstr = fcx.infcx().ty_to_string(t_cast);
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let mut err = fcx.type_error_struct(span, |actual| {
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format!("cast to unsized type: `{}` as `{}`", actual, tstr)
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@ -0,0 +1,22 @@
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// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Coherence error results because we do not know whether `T: Foo<P>` or not
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// for the second impl.
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use std::marker::PhantomData;
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pub trait Foo<P> {}
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impl <P, T: Foo<P>> Foo<P> for Option<T> {} //~ ERROR E0119
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impl<T, U> Foo<T> for Option<U> { }
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fn main() {}
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@ -22,7 +22,7 @@ use std::{u8, u16, u32, u64, usize};
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const A_I8_T
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: [u32; (i8::MAX as i8 + 1u8) as usize]
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//~^ ERROR mismatched types
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//~| the trait `core::ops::Add<u8>` is not implemented for the type `i8`
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//~| ERROR the trait `core::ops::Add<u8>` is not implemented for the type `i8`
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= [0; (i8::MAX as usize) + 1];
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fn main() {
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@ -12,7 +12,7 @@ struct Homura;
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fn akemi(homura: Homura) {
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let Some(ref madoka) = Some(homura.kaname()); //~ ERROR no method named `kaname` found
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madoka.clone(); //~ ERROR the type of this value must be known in this context
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madoka.clone();
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}
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fn main() { }
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@ -16,5 +16,5 @@ fn main() {
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let x = &10 as
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&Add;
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//~^ ERROR the type parameter `RHS` must be explicitly specified in an object type because its default value `Self` references the type `Self`
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//~^^ ERROR the value of the associated type `Output` (from the trait `core::ops::Add`) must be specified
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//~| ERROR the value of the associated type `Output` (from the trait `core::ops::Add`) must be specified
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}
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@ -9,5 +9,7 @@
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// except according to those terms.
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fn main() {
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"".chars().fold(|_, _| (), ()); //~ ERROR is not implemented for the type `()`
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"".chars().fold(|_, _| (), ());
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//~^ ERROR E0277
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//~| ERROR E0277
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}
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@ -10,5 +10,5 @@
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fn main() {
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1.0f64 - 1.0;
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1.0f64 - 1 //~ ERROR: is not implemented
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1.0f64 - 1 //~ ERROR E0277
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}
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@ -8,11 +8,14 @@
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![feature(rustc_attrs)]
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use std::marker::PhantomData;
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pub trait Foo<P> {}
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impl <P, T: Foo<P>> Foo<P> for Option<T> {} //~ ERROR E0119
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impl <P, T: Foo<P>> Foo<P> for Option<T> {}
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pub struct Qux<T> (PhantomData<*mut T>);
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@ -24,4 +27,5 @@ pub trait Bar {
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impl<T: 'static, W: Bar<Output = T>> Foo<*mut T> for W {}
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fn main() {}
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#[rustc_error]
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fn main() {} //~ ERROR compilation successful
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@ -32,5 +32,4 @@ fn main() {
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let p = Point::new(0.0, 0.0);
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//~^ ERROR no associated item named `new` found for type `Point` in the current scope
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println!("{}", p.to_string());
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//~^ ERROR the type of this value must be known in this context
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}
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