Rework diagnostics for wrong number of generic args (fixes #66228 and #71924) #77524

Patryk27 · 2020-10-04T11:27:11Z

This PR reworks the wrong number of {} arguments message, so that it provides more details and contextual hints.

rust-highfive · 2020-10-04T11:27:15Z

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Patryk27 · 2020-10-08T20:57:42Z

Ping, ping, just remindin' - @matthewjasper :-)

bors · 2020-10-14T05:27:54Z

☔ The latest upstream changes (presumably #77926) made this pull request unmergeable. Please resolve the merge conflicts.

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Patryk27 · 2020-10-17T15:34:51Z

@rustbot modify labels: +S-waiting-on-review -S-waiting-on-author

Patryk27 · 2020-10-17T20:49:19Z

also, re-pinging @matthewjasper :-)

bors · 2020-10-20T05:48:50Z

☔ The latest upstream changes (presumably #78127) made this pull request unmergeable. Please resolve the merge conflicts.

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Patryk27 · 2020-10-21T19:32:49Z

@rustbot modify labels: +S-waiting-on-review -S-waiting-on-author

bors · 2020-10-26T23:39:41Z

☔ The latest upstream changes (presumably #77187) made this pull request unmergeable. Please resolve the merge conflicts.

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Patryk27 · 2020-10-27T17:34:18Z

r? @estebank

Patryk27 · 2020-11-08T20:12:55Z

ping ping @estebank

bors · 2020-11-15T15:53:05Z

☔ The latest upstream changes (presumably #79070) made this pull request unmergeable. Please resolve the merge conflicts.

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Patryk27 · 2020-11-16T19:33:13Z

ping ping @estebank, @jonas-schievink? (sorry, I'm not quite sure who to ping or how to proceed from here 😅)

jonas-schievink · 2020-11-16T20:01:53Z

The triage working group would pick this up if it doesn't get updated in a while, but every time you comment that time gets reset

estebank

Apologies for the delay in reviewing. I'll finish the review shortly, but in order to avoid keeping you waiting any further giving the length of the PR, I am pushing out some of the things I've found so far.

estebank · 2020-11-25T01:29:36Z

src/test/ui/unboxed-closures/unboxed-closure-sugar-wrong-trait.stderr

+LL | trait Trait {}
+   | ----------- defined here, with 0 type parameters


src/test/ui/unboxed-closures/unboxed-closure-sugar-wrong-trait.stderr

src/test/ui/unboxed-closures/unboxed-closure-sugar-wrong-number-number-type-parameters.stderr

src/test/ui/async-await/issues/issue-65159.stderr

src/test/ui/bad/bad-mid-path-type-params.stderr

estebank · 2020-11-25T02:08:38Z

compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs

+            format!("consider removing this {} argument", self.kind)
+        };
+
+        err.span_suggestion(span, &msg, String::new(), Applicability::MaybeIncorrect);


I'm wondering if making this

Suggested change

err.span_suggestion(span, &msg, String::new(), Applicability::MaybeIncorrect);

err.span_suggestion_verbose(span, &msg, String::new(), Applicability::MaybeIncorrect);

will look better.

Seems like span_suggestion_verbose() prints message with the suggestion already applied, yielding pearls such as:

@@ -19,7 +19,12 @@ LL | fn foo<const X: usize, const Y: usize>() -> usize { | ------------------------------------------------- defined here, with 2 const parameters: `X`, `Y` ... LL | foo::<0, 0, 0>(); - | ^^^ --- help: remove this const argument + | ^^^ + | +help: remove this const argument + | +LL | foo::<0, 0>(); + | --

or

@@ -25,7 +30,12 @@ LL | struct S; | --------- defined here, with 0 const parameters ... LL | S::<0>; - | ^ - help: remove this const argument + | ^ + | +help: remove this const argument + | +LL | S::<>; + | --

IMHO the inline (current) version with s/consider replacing/replace is way more legible.

compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs

src/test/ui/const-generics/invalid-enum.stderr

rust-log-analyzer · 2021-01-02T20:12:48Z

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

configure: rust.channel         := nightly
configure: rust.debug-assertions := True
configure: llvm.assertions      := True
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
Checking which error codes lack tests...
Found 435 error codes
Found 0 error codes with no tests
Done!
tidy error: /checkout/src/test/ui/async-await/issues/issue-65159.rs:5: line longer than 100 chars
tidy error: /checkout/src/test/ui/traits/trait-test-2.rs: ignoring line length unnecessarily
tidy error: /checkout/src/test/ui/seq-args.rs:4: line longer than 100 chars
tidy error: /checkout/src/test/ui/seq-args.rs:7: line longer than 100 chars
tidy error: /checkout/src/test/ui/const-generics/incorrect-number-of-const-args.rs:11: line longer than 100 chars
tidy error: /checkout/src/test/ui/const-generics/incorrect-number-of-const-args.rs:12: line longer than 100 chars
tidy error: /checkout/src/test/ui/const-generics/invalid-const-arg-for-type-param.rs:6: line longer than 100 chars
tidy error: /checkout/src/test/ui/methods/method-call-lifetime-args-fail.rs:17: line longer than 100 chars
tidy error: /checkout/src/test/ui/methods/method-call-lifetime-args-fail.rs:19: line longer than 100 chars
tidy error: /checkout/src/test/ui/methods/method-call-lifetime-args-fail.rs:64: line longer than 100 chars
tidy error: /checkout/src/test/ui/methods/method-call-lifetime-args-fail.rs:66: line longer than 100 chars
tidy error: /checkout/src/test/ui/issues/issue-18423.rs:4: line longer than 100 chars
tidy error: /checkout/src/test/ui/issues/issue-53251.rs:12: line longer than 100 chars
tidy error: /checkout/src/test/ui/issues/issue-53251.rs:13: line longer than 100 chars
tidy error: /checkout/src/test/ui/structs/structure-constructor-type-mismatch.rs:48: line longer than 100 chars
tidy error: /checkout/src/test/ui/structs/structure-constructor-type-mismatch.rs:54: line longer than 100 chars
some tidy checks failed

command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "/checkout/obj/build"
expected success, got: exit code: 1

compiler/rustc_hir/src/hir.rs

estebank · 2021-01-08T01:20:48Z

src/test/ui/unboxed-closures/unboxed-closure-sugar-wrong-trait.stderr

@@ -1,8 +1,16 @@
-error[E0107]: wrong number of type arguments: expected 0, found 1
+error[E0107]: this trait takes 0 type arguments but 1 type argument was supplied


Ideally we would give the error for non-Fn trait using parenthetical notation higher priority and emit it instead of these two, but that should be done in a different PR.

estebank · 2021-01-08T01:22:12Z

src/test/ui/unboxed-closures/unboxed-closure-sugar-used-on-struct.stderr

+help: use angle brackets to add missing type argument
+   |
+LL | fn foo(b: Box<Bar<A>()>) {
+   |                  ^^^


Because of the (incorrect) use of the parenthetical notation here, the suggestion is incorrect. That being said it might be worth it to tackle it at another time.

estebank · 2021-01-08T01:28:04Z

src/test/ui/const-generics/issues/issue-76595.stderr

+note: function defined here, with 2 generic parameters: `T`, `P`
+  --> $DIR/issue-76595.rs:10:4
+   |
+LL | fn test<T, const P: usize>() where Bool<{core::mem::size_of::<T>() > 4}>: True {
+   |    ^^^^ -        -
+help: add missing generic argument
+   |
+LL |     test::<2, P>();
+   |             ^^^


I see here that we don't try to match and differentiate between type, lifetime and const params, but that is fine for this PR, I'd like to land it sooner rather than later. We'll have to take a look at refining that later.

Actually, the first version of this message did distinguish between type, lifetime and const parameters; it was changed some time ago on the upstream:

rust/compiler/rustc_typeck/src/astconv/generics.rs

Line 502 in 34628e5

"generic"

... and I just went with it.

estebank · 2021-01-08T01:29:55Z

src/test/ui/constructor-lifetime-args.stderr

+help: add missing lifetime argument
+   |
+LL |     S::<'static, 'b>(&0, &0);
+   |                ^^^^


For lifetimes we would ideally look for available lifetimes (like we do in other cases) and if none use 'static, but again, that should be follow up work. (I'm just marking TODO notes for later right now.)

Parallel idea: for lifetime & type generics in expression position (e.g. .collect::<Vec>()) we could suggest using placeholders (i.e. suggest Vec<_> instead of Vec<T>).

src/test/ui/generics/generic-arg-mismatch-recover.stderr

estebank · 2021-01-08T01:34:03Z

src/test/ui/generics/wrong-number-of-args.stderr

+error[E0107]: this struct takes 0 lifetime arguments but 1 lifetime argument was supplied
+  --> $DIR/wrong-number-of-args.rs:10:14
+   |
+LL |     type C = Ty<'static, usize>;
+   |              ^^ --------- help: remove this lifetime argument
+   |              |
+   |              expected 0 lifetime arguments
+   |
+note: struct defined here, with 0 lifetime parameters
+  --> $DIR/wrong-number-of-args.rs:2:12
+   |
+LL |     struct Ty;
+   |            ^^
+
+error[E0107]: this struct takes 0 type arguments but 1 type argument was supplied
+  --> $DIR/wrong-number-of-args.rs:10:14
+   |
+LL |     type C = Ty<'static, usize>;
+   |              ^^        ------- help: remove this type argument
+   |              |
+   |              expected 0 type arguments
+   |
+note: struct defined here, with 0 type parameters
+  --> $DIR/wrong-number-of-args.rs:2:12
+   |
+LL |     struct Ty;
+   |            ^^


Ideally we would tackle these two with the same error, suggesting to remove the entirety of the arguments at once, but again, this can be done later, it is not a regression.

estebank · 2021-01-13T18:56:39Z

src/test/ui/typeck/typeck-builtin-bound-type-parameters.stderr

+error[E0107]: this trait takes 0 lifetime arguments but 1 lifetime argument was supplied
+  --> $DIR/typeck-builtin-bound-type-parameters.rs:13:15
   |
 LL | fn foo2<'a, T:Copy<'a, U>, U>(x: T) {}
-   |                    ^^ unexpected lifetime argument
+   |               ^^^^ ---- help: remove this lifetime argument
+   |               |
+   |               expected 0 lifetime arguments
+   |
+note: trait defined here, with 0 lifetime parameters
+  --> $SRC_DIR/core/src/marker.rs:LL:COL
+   |
+LL | pub trait Copy: Clone {
+   |           ^^^^

-error[E0107]: wrong number of type arguments: expected 0, found 1
-  --> $DIR/typeck-builtin-bound-type-parameters.rs:14:24
+error[E0107]: this trait takes 0 type arguments but 1 type argument was supplied
+  --> $DIR/typeck-builtin-bound-type-parameters.rs:13:15
   |
 LL | fn foo2<'a, T:Copy<'a, U>, U>(x: T) {}
-   |                        ^ unexpected type argument
+   |               ^^^^   --- help: remove this type argument
+   |               |
+   |               expected 0 type arguments
+   |
+note: trait defined here, with 0 type parameters
+  --> $SRC_DIR/core/src/marker.rs:LL:COL
+   |
+LL | pub trait Copy: Clone {
+   |           ^^^^


This case is somewhat unfortunate (because we would need to look at the whole thing and suggest removing both lifetimes and type params in one go, but we don't need to tackle it now.

I was thinking about a dedicated message for when generics were provided where none were expected, something in the lines of:

error[E0107]: this trait is not generic --> $DIR/typeck-builtin-bound-type-parameters.rs:13:15 | LL | fn foo2<'a, T:Copy<'a, U>, U>(x: T) {} | ^^^^------- help: remove these generics | note: trait defined here, with no generics --> $SRC_DIR/core/src/marker.rs:LL:COL | LL | pub trait Copy: Clone { | ^^^^

I'll try tackling it in another PR, after this one gets merged :-)

estebank · 2021-01-13T18:58:01Z

src/test/ui/type-alias-enum-variants/enum-variant-priority-higher-than-other-inherent.stderr

-   |
-note: tuple variant defined here
-  --> $DIR/enum-variant-priority-higher-than-other-inherent.rs:5:5
-   |
-LL |     V(u8)
-   |     ^^^^^


Somewhat surprised by this change 👀

Yes, it's a bit unfortunate side effect of looking up identifiers via a new query - def_ident_span - that I haven't been able to re-implement for tuple variants. Technically reviving this one should be as easy as improving that query.

estebank · 2021-01-13T19:01:31Z

@bors r+ rollup=never

bors · 2021-01-13T19:01:34Z

📌 Commit d2f8e39 has been approved by estebank

bors · 2021-01-13T20:36:05Z

⌛ Testing commit d2f8e39 with merge a62a760...

bors · 2021-01-13T23:24:24Z

☀️ Test successful - checks-actions
Approved by: estebank
Pushing a62a760 to master...

Rework diagnostics for wrong number of generic args (fixes rust-lang#66228 and rust-lang#71924) This PR reworks the `wrong number of {} arguments` message, so that it provides more details and contextual hints.

rust-highfive assigned matthewjasper Oct 4, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 4, 2020

Patryk27 force-pushed the fixes/66228 branch 6 times, most recently from 17ca2ab to ea0a68d Compare October 4, 2020 17:40

Patryk27 force-pushed the fixes/66228 branch from ea0a68d to 124d0f2 Compare October 17, 2020 15:34

Patryk27 force-pushed the fixes/66228 branch from 124d0f2 to 3ca04da Compare October 21, 2020 19:31

Patryk27 force-pushed the fixes/66228 branch from 3ca04da to ec2b6ea Compare October 27, 2020 17:33

rust-highfive assigned estebank and unassigned matthewjasper Oct 27, 2020

Patryk27 force-pushed the fixes/66228 branch from ec2b6ea to 1028d4f Compare November 16, 2020 19:30

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Rework diagnostics for wrong number of generic args

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This was referenced Jan 13, 2021

Better method call error messages #71827

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Refactor Binder to track bound vars #76814

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Generic associated types in trait paths #79554

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Patryk27 deleted the fixes/66228 branch January 14, 2021 06:01

jackh726 mentioned this pull request Feb 5, 2021

Bad diagnostics for GATs in trait paths #81801

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Tracking issue for const generics (RFC 2000) #44580

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Rework diagnostics for wrong number of generic args (fixes #66228 and #71924) #77524

Rework diagnostics for wrong number of generic args (fixes #66228 and #71924) #77524

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		LL \| trait Trait {}
		\| ----------- defined here, with 0 type parameters

	err.span_suggestion(span, &msg, String::new(), Applicability::MaybeIncorrect);
	err.span_suggestion_verbose(span, &msg, String::new(), Applicability::MaybeIncorrect);

		@@ -1,8 +1,16 @@
		error[E0107]: wrong number of type arguments: expected 0, found 1
		error[E0107]: this trait takes 0 type arguments but 1 type argument was supplied

Rework diagnostics for wrong number of generic args (fixes #66228 and #71924) #77524

Rework diagnostics for wrong number of generic args (fixes #66228 and #71924) #77524

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