give some suggestion for returning anonymous enum #100988

LYF1999 · 2022-08-25T07:59:36Z

give some suggestion for returning anonymous enum

fn foo<'a>() -> i32 | Vec<i32> | &str | &'a String | Foo {
                         ^ help: consider using enum as return type: `SomeEnum`
   = note: enum SomeEnum<'lifetime,'a>{
               I32(i32)
               Vec(Vec<...>)
               StrRef(&'lifetime str)
               StringRef(&'a String)
               Foo(Foo)
           }

fix #100741
r? @estebank

LYF1999 · 2022-08-25T08:00:31Z

should we create a crate for some util functions like to_camel_case?

estebank · 2022-09-01T17:11:40Z

compiler/rustc_parse/src/parser/diagnostics.rs

+            "SomeEnum",
+            Applicability::HasPlaceholders,
+        )
+        .note(suggestion_code);


Instead of the note with the enum, we could instead use a multipart_suggestion and pass in the span for the space right at the start of the item, so that the output can be

error: anonymous enums are not supported --> $DIR/issue-100741-return-anonymous-enum.rs:3:17 | LL | fn foo<'a>() -> i32 | Vec<i32> | &str | &'a String | Foo { | ^ ^ ^ ^ not supported in types | help: consider using enum as return type | LL + enum SomeEnum<'lifetime,'a>{ LL + I32(i32) LL + Vec(Vec<i32>) LL + StrRef(&'lifetime str) LL + StringRef(&'a String) LL + Foo(Foo) LL + } LL ~ fn foo<'a>() -> SomeEnum<'_, 'a> { |

estebank · 2022-09-01T17:12:39Z

compiler/rustc_parse/src/parser/diagnostics.rs

+        err.span_suggestion(
+            span,
+            "consider using enum as return type",
+            "SomeEnum",


You need to account for the lifetimes that were mentioned. In the test included, this would end up being '_, 'a.

estebank · 2022-09-01T17:13:17Z

compiler/rustc_parse/src/parser/diagnostics.rs

+
+                        if let Some(_args) = &seg.args {
+                            ty_string.push('<');
+                            ty_string.push_str("...");


Why don't we print the whole type?

it's more complicated, for example Vec<impl Send> | Vec<(i32, i64)>. We can not make a enum variant name for these type.

As you propose, we can use Variant{N} as the variant name

estebank · 2022-09-01T17:20:42Z

compiler/rustc_parse/src/parser/diagnostics.rs

+                    let mut ty_string = String::new();
+
+                    if let Some(seg) = path.segments.iter().last() {
+                        name.push_str(seg.ident.name.as_str());


It feels like the only thing we need here is the name and for ty_string format!("{ty}") is enough, after folding the anon lifetimes to be named as 'lifetime, in way similar to what is done here:

rust/compiler/rustc_middle/src/ty/erase_regions.rs

Lines 56 to 69 in c3fce8e

fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {

// because late-bound regions affect subtyping, we can't

// erase the bound/free distinction, but we can replace

// all free regions with 'erased.

//

// Note that we *CAN* replace early-bound regions -- the

// type system never "sees" those, they get substituted

// away. In codegen, they will always be erased to 'erased

// whenever a substitution occurs.

match *r {

ty::ReLateBound(..) => r,

_ => self.tcx.lifetimes.re_erased,

}

}

emmm, the TyKind in rustc_ast doesn't implement Display, if it's nesscery to implement Display, I will submit a new pull request to do that.

I'm fairly certain there's a way to pprint TyKind, but it isn't through Display directly 🤔

estebank · 2022-09-01T17:22:40Z

compiler/rustc_parse/src/parser/diagnostics.rs

+                        None
+                    }
+                }
+                _ => None,


This wouldn't work for something like -> [i32; 10] | Vec<i32>, right?

If you don't want to support every TyKind, you can at least provide a Variant{N} name so that the suggested enum makes syntactic sense.

estebank · 2022-09-01T17:38:23Z

compiler/rustc_parse/src/parser/ty.rs

+            let mut tys = vec![];
+            let lo = self.token.span;
+            loop {


The issue with this that we shouldn't recover this only for return types, we should be doing this further down, in parse_ty_common, maybe adding another argument to it to explicitly state what should be coming after it (to support things like let foo: A | B = ...;).

estebank · 2022-09-01T17:39:57Z

compiler/rustc_parse/src/utils.rs

+    u.next().is_some()
+}
+
+pub fn to_camel_case(s: &str) -> String {


rust/compiler/rustc_lint/src/nonstandard_style.rs

Line 90 in dcd5177

fn to_camel_case(s: &str) -> String {

but it's in crate rustc_lint. I think it's weird to make rustc_parse depend rustc_lint. Should we create a crate rustc_utils for these functions like to_camel_case

We could move this to a shared dependency of the two, like rustc_errors.

bors · 2023-01-26T09:34:07Z

☔ The latest upstream changes (presumably #107314) made this pull request unmergeable. Please resolve the merge conflicts.

Noratrieb · 2023-03-14T11:29:53Z

any updates here? we have to be very careful to not recover on the happy path as to not cause further regressions

LYF1999 · 2023-03-14T13:39:02Z

sorry, I am not working on it currently

bors · 2023-05-02T13:17:34Z

☔ The latest upstream changes (presumably #109128) made this pull request unmergeable. Please resolve the merge conflicts.

Dylan-DPC · 2023-05-15T09:37:08Z

Closing this as inactive. Feel free to reöpen this pr or create a new pr if you get the time to work on this. Thanks

rust-highfive assigned estebank Aug 25, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Aug 25, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 25, 2022

LYF1999 force-pushed the yf/issue-100741 branch from f615844 to ca90121 Compare August 25, 2022 08:18

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LYF1999 force-pushed the yf/issue-100741 branch from ca90121 to d436357 Compare August 25, 2022 08:55

give some suggestion for returning anonymous enum

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LYF1999 force-pushed the yf/issue-100741 branch from d436357 to bac60db Compare August 25, 2022 09:19

estebank reviewed Sep 1, 2022

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LYF1999 marked this pull request as draft September 22, 2022 07:30

estebank added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 10, 2022

nicopap mentioned this pull request Jan 30, 2023

Closure with a typed function argument and top level struct constructor break in nightly #107461

Closed

Dylan-DPC closed this May 15, 2023

Dylan-DPC added S-inactive Status: Inactive and waiting on the author. This is often applied to closed PRs. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 15, 2023

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give some suggestion for returning anonymous enum #100988

give some suggestion for returning anonymous enum #100988

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bors commented Jan 26, 2023

Noratrieb commented Mar 14, 2023

LYF1999 commented Mar 14, 2023

bors commented May 2, 2023

Dylan-DPC commented May 15, 2023

	fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
	// because late-bound regions affect subtyping, we can't
	// erase the bound/free distinction, but we can replace
	// all free regions with 'erased.
	//
	// Note that we CAN replace early-bound regions -- the
	// type system never "sees" those, they get substituted
	// away. In codegen, they will always be erased to 'erased
	// whenever a substitution occurs.
	match *r {
	ty::ReLateBound(..) => r,
	_ => self.tcx.lifetimes.re_erased,
	}
	}

give some suggestion for returning anonymous enum #100988

give some suggestion for returning anonymous enum #100988

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bors commented Jan 26, 2023

Noratrieb commented Mar 14, 2023

LYF1999 commented Mar 14, 2023

bors commented May 2, 2023

Dylan-DPC commented May 15, 2023