Point out the known type when field doesn't satisfy bound #38150

estebank · 2016-12-03T23:09:42Z

For file

use std::path::Path;

fn f(p: Path) { }

provide the following error

error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `std::path::Path`
 --> file.rs:3:6
  |
3 | fn f(p: Path) { }
  |      ^ within `std::path::Path`, the trait `std::marker::Sized` is not implemented for `[u8]`
  |
  = note: `[u8]` does not have a constant size known at compile-time
  = note: required because it appears within the type `std::path::Path`
  = note: all local variables must have a statically known size

Fix #23286.

rust-highfive · 2016-12-03T23:09:55Z

r? @nikomatsakis

(rust_highfive has picked a reviewer for you, use r? to override)

GuillaumeGomez · 2016-12-07T08:28:16Z

src/librustc/traits/error_reporting.rs

+                                let (post_message, pre_message) =
+                                    if let ObligationCauseCode::BuiltinDerivedObligation(ref data)
+                                        = obligation.cause.code
+                                {


This brace should be on the previous line.

For file ```rust use std::path::Path; fn f(p: Path) { } ``` provide the following error ```nocode error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `std::path::Path` --> file.rs:3:6 | 3 | fn f(p: Path) { } | ^ within `std::path::Path`, the trait `std::marker::Sized` is not implemented for `[u8]` | = note: `[u8]` does not have a constant size known at compile-time = note: required because it appears within the type `std::path::Path` = note: all local variables must have a statically known size ```

GuillaumeGomez · 2016-12-08T19:45:25Z

src/librustc/traits/error_reporting.rs

+                                let (post_message, pre_message) =
+                                    if let ObligationCauseCode::BuiltinDerivedObligation(ref data)
+                                        = obligation.cause.code {
+                                    let parent_trait_ref = self.resolve_type_vars_if_possible(


Missing an indent level here.

Is it? the if let is part of the previous line, the only reason is below is because I couldn't get to fit nicely in under 100 chars. In this were to fit in one line it would be:

let (post_message, pre_message) = if let ObligationCauseCode::BuiltinDerivedObligation(ref data) = obligation.cause.code {

I don't see why then line 493 would have to have double indentation. :)

I agree that it is slightly confusing as it is now, but haven't come up with a better way of presenting this.

Oh indeed, you're absolutely right, my bad!

one better way might be using match :)

let (post_message, pre_message) = match obligation.cause.code { ObligationCauseCode::BuiltinDerivedObligation(ref data) => { let parent_trait_ref = self.resolve_type_vars_if_possible( ... } _ => { (String::new(), String::new()) } };

GuillaumeGomez · 2016-12-09T00:24:49Z

All good for me. I'm not sure I'm supposed to merge this so I'll wait for others' opinion.

cc @jonathandturner

nikomatsakis · 2016-12-09T14:43:03Z

src/librustc/traits/error_reporting.rs

+                                let (post_message, pre_message) =
+                                    if let ObligationCauseCode::BuiltinDerivedObligation(ref data)
+                                        = obligation.cause.code {
+                                    let parent_trait_ref = self.resolve_type_vars_if_possible(


one better way might be using match :)

let (post_message, pre_message) = match obligation.cause.code { ObligationCauseCode::BuiltinDerivedObligation(ref data) => { let parent_trait_ref = self.resolve_type_vars_if_possible( ... } _ => { (String::new(), String::new()) } };

nikomatsakis · 2016-12-09T14:45:49Z

src/librustc/traits/error_reporting.rs

+                                        = obligation.cause.code {
+                                    let parent_trait_ref = self.resolve_type_vars_if_possible(
+                                        &data.parent_trait_ref);
+                                    (format!(" in `{}`", parent_trait_ref.0.self_ty()),


One concern I have is that this only goes up one level, but there are similar cases where multiple levels are needed. For example, it'd be nice if this patch addressed this example: https://is.gd/BZjfP6

The current output is

error[E0277]: the trait bound `*const u8: std::marker::Send` is not satisfied --> <anon>:16:5 | 16 | is_send::<Foo>(); | ^^^^^^^^^^^^^^ trait `*const u8: std::marker::Send` not satisfied | = note: `*const u8` cannot be sent between threads safely = note: required because it appears within the type `Baz` = note: required because it appears within the type `Bar` = note: required because it appears within the type `Foo` = note: required by `is_send`

and I think your suggested approach would be a big improvement:

error[E0277]: within `Foo`, the trait bound `*const u8: std::marker::Send` is not satisfied --> <anon>:16:5 | 16 | is_send::<Foo>(); | ^^^^^^^^^^^^^^ trait `*const u8: std::marker::Send` not satisfied | = note: `*const u8` cannot be sent between threads safely = note: required because it appears within the type `Baz` = note: required because it appears within the type `Bar` = note: required because it appears within the type `Foo` = note: required by `is_send`

But I believe your patch as is will print "within Baz" instead.

should be easy enough though -- just have to iterate on the cause chain rather than just going up one level.

Added test for new case and a recursive search up the cause chain.

nikomatsakis · 2016-12-19T20:45:14Z

@bors r+

bors · 2016-12-19T20:45:14Z

📌 Commit 5c13041 has been approved by nikomatsakis

bors · 2016-12-20T02:08:48Z

⌛ Testing commit 5c13041 with merge 27122ab...

bors · 2016-12-20T02:11:46Z

💔 Test failed - auto-win-gnu-64-opt

alexcrichton · 2016-12-20T17:45:46Z

@bors: retry

…

On Mon, Dec 19, 2016 at 6:11 PM, bors ***@***.***> wrote: 💔 Test failed - auto-win-gnu-64-opt <https://buildbot.rust-lang.org/builders/auto-win-gnu-64-opt/builds/6460> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#38150 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD95LptLW_NJMW6wRoRfGy0H5S-uZ07ks5rJzlkgaJpZM4LDcVM> .

Point out the known type when field doesn't satisfy bound For file ```rust use std::path::Path; fn f(p: Path) { } ``` provide the following error ```nocode error[E0277]: the trait bound `[u8]: std::marker::Sized` is not satisfied in `std::path::Path` --> file.rs:3:6 | 3 | fn f(p: Path) { } | ^ within `std::path::Path`, the trait `std::marker::Sized` is not implemented for `[u8]` | = note: `[u8]` does not have a constant size known at compile-time = note: required because it appears within the type `std::path::Path` = note: all local variables must have a statically known size ``` Fix rust-lang#23286.

Rollup of 29 pull requests - Successful merges: #37761, #38006, #38131, #38150, #38158, #38171, #38208, #38215, #38236, #38245, #38289, #38302, #38315, #38346, #38388, #38395, #38398, #38418, #38432, #38451, #38463, #38468, #38470, #38471, #38472, #38478, #38486, #38493, #38498 - Failed merges: #38271, #38483

rust-highfive assigned nikomatsakis Dec 3, 2016

estebank force-pushed the fix-23286 branch from a002515 to 249ac37 Compare December 4, 2016 01:41

GuillaumeGomez reviewed Dec 7, 2016

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estebank force-pushed the fix-23286 branch from 249ac37 to ef09db0 Compare December 8, 2016 18:25

GuillaumeGomez requested changes Dec 8, 2016

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GuillaumeGomez approved these changes Dec 9, 2016

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nikomatsakis requested changes Dec 9, 2016

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review comments

5c13041

estebank force-pushed the fix-23286 branch from 567e7fd to 5c13041 Compare December 14, 2016 21:46

nikomatsakis approved these changes Dec 19, 2016

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alexcrichton mentioned this pull request Dec 20, 2016

Rollup of 29 pull requests #38499

Merged

bors merged commit 5c13041 into rust-lang:master Dec 21, 2016

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Point out the known type when field doesn't satisfy bound #38150

Point out the known type when field doesn't satisfy bound #38150

estebank commented Dec 3, 2016

rust-highfive commented Dec 3, 2016

GuillaumeGomez Dec 7, 2016

estebank Dec 8, 2016

GuillaumeGomez Dec 8, 2016

estebank Dec 8, 2016 •

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GuillaumeGomez Dec 9, 2016

nikomatsakis Dec 9, 2016

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nikomatsakis Dec 9, 2016

nikomatsakis Dec 9, 2016

estebank Dec 12, 2016

nikomatsakis commented Dec 19, 2016

bors commented Dec 19, 2016

bors commented Dec 20, 2016

bors commented Dec 20, 2016

alexcrichton commented Dec 20, 2016 via email

Point out the known type when field doesn't satisfy bound #38150

Point out the known type when field doesn't satisfy bound #38150

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estebank commented Dec 3, 2016

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estebank Dec 8, 2016 • edited Loading

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nikomatsakis commented Dec 19, 2016

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estebank Dec 8, 2016 •

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