From 4d8d68f80d2fb474188c1c2ee26d6266b4eaa003 Mon Sep 17 00:00:00 2001 From: Ariel Ben-Yehuda Date: Tue, 5 May 2015 22:09:17 +0300 Subject: [PATCH 1/3] Fix #25076 --- src/librustc/middle/traits/error_reporting.rs | 8 +++++-- src/librustc/middle/traits/project.rs | 5 ++++- src/test/compile-fail/issue-25076.rs | 21 +++++++++++++++++++ 3 files changed, 31 insertions(+), 3 deletions(-) create mode 100644 src/test/compile-fail/issue-25076.rs diff --git a/src/librustc/middle/traits/error_reporting.rs b/src/librustc/middle/traits/error_reporting.rs index 1b5719d3d42..7d69df73cd2 100644 --- a/src/librustc/middle/traits/error_reporting.rs +++ b/src/librustc/middle/traits/error_reporting.rs @@ -56,7 +56,10 @@ pub fn report_projection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>, { let predicate = infcx.resolve_type_vars_if_possible(&obligation.predicate); - if !predicate.references_error() { + // The ty_err created by normalize_to_error can end up being unified + // into all obligations - we still have to report an error in that + // case. + if !infcx.tcx.sess.has_errors() || !predicate.references_error() { span_err!(infcx.tcx.sess, obligation.cause.span, E0271, "type mismatch resolving `{}`: {}", predicate.user_string(infcx.tcx), @@ -183,7 +186,8 @@ pub fn report_selection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>, let trait_predicate = infcx.resolve_type_vars_if_possible(trait_predicate); - if !trait_predicate.references_error() { + if !infcx.tcx.sess.has_errors() || + !trait_predicate.references_error() { let trait_ref = trait_predicate.to_poly_trait_ref(); span_err!(infcx.tcx.sess, obligation.cause.span, E0277, "the trait `{}` is not implemented for the type `{}`", diff --git a/src/librustc/middle/traits/project.rs b/src/librustc/middle/traits/project.rs index 8ae7ad029ac..f6bde80e298 100644 --- a/src/librustc/middle/traits/project.rs +++ b/src/librustc/middle/traits/project.rs @@ -408,7 +408,10 @@ fn opt_normalize_projection_type<'a,'b,'tcx>( } /// in various error cases, we just set ty_err and return an obligation -/// that, when fulfilled, will lead to an error +/// that, when fulfilled, will lead to an error. +/// +/// FIXME: the ty_err created here can enter the obligation we create, +/// leading to error messages involving ty_err. fn normalize_to_error<'a,'tcx>(selcx: &mut SelectionContext<'a,'tcx>, projection_ty: ty::ProjectionTy<'tcx>, cause: ObligationCause<'tcx>, diff --git a/src/test/compile-fail/issue-25076.rs b/src/test/compile-fail/issue-25076.rs new file mode 100644 index 00000000000..40f3b728496 --- /dev/null +++ b/src/test/compile-fail/issue-25076.rs @@ -0,0 +1,21 @@ +// Copyright 2015 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 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +struct S; + +trait InOut { type Out; } + +fn do_fold>(init: B, f: F) {} + +fn bot() -> T { loop {} } + +fn main() { + do_fold(bot(), ()); //~ ERROR is not implemented for the type `()` +} From df42976e4db6565e8693460c34387e515d10ecfd Mon Sep 17 00:00:00 2001 From: Ariel Ben-Yehuda Date: Wed, 6 May 2015 22:24:13 +0300 Subject: [PATCH 2/3] improve comment --- src/librustc/middle/traits/error_reporting.rs | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/librustc/middle/traits/error_reporting.rs b/src/librustc/middle/traits/error_reporting.rs index 7d69df73cd2..ea29c48983f 100644 --- a/src/librustc/middle/traits/error_reporting.rs +++ b/src/librustc/middle/traits/error_reporting.rs @@ -57,8 +57,10 @@ pub fn report_projection_error<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>, let predicate = infcx.resolve_type_vars_if_possible(&obligation.predicate); // The ty_err created by normalize_to_error can end up being unified - // into all obligations - we still have to report an error in that - // case. + // into all obligations: for example, if our obligation is something + // like `$X = <() as Foo<$X>>::Out` and () does not implement Foo<_>, + // then $X will be unified with ty_err, but the error still needs to be + // reported. if !infcx.tcx.sess.has_errors() || !predicate.references_error() { span_err!(infcx.tcx.sess, obligation.cause.span, E0271, "type mismatch resolving `{}`: {}", From ea3747902cb29338878a1e497b8c28f344c4fc6a Mon Sep 17 00:00:00 2001 From: Ariel Ben-Yehuda Date: Thu, 7 May 2015 16:19:43 +0300 Subject: [PATCH 3/3] fix test --- src/test/compile-fail/issue-23966.rs | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/src/test/compile-fail/issue-23966.rs b/src/test/compile-fail/issue-23966.rs index 18b51368665..d7f909e4ebc 100644 --- a/src/test/compile-fail/issue-23966.rs +++ b/src/test/compile-fail/issue-23966.rs @@ -9,6 +9,5 @@ // except according to those terms. fn main() { - "".chars().fold(|_, _| (), ()); - //~^ ERROR cannot determine a type for this expression: unconstrained type + "".chars().fold(|_, _| (), ()); //~ ERROR is not implemented for the type `()` }