Suggest to use . instead of :: when accessing a method of an object #101975

chenyukang · 2022-09-18T11:45:14Z

Fixes #101749
Fixes #101542

rust-highfive · 2022-09-18T11:45:17Z

r? @TaKO8Ki

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TaKO8Ki

Sorry for the late review. I left a comment.

TaKO8Ki · 2022-10-05T20:09:14Z

src/test/ui/resolve/issue-101749.stderr

+LL |     println!("{}", rect1::area());
+   |                    ^^^^^ use of undeclared crate or module `rect1`
+   |
+help: `rect1` is not a crate or module, maybe you meant to call instance method


I think this suggestion is emitted if rect1 does not have area method. Is it possible to check if rect has it before creating suggestion?

Given the following code:

// run-rustfix struct Rectangle { width: i32, height: i32, } impl Rectangle { fn new(width: i32, height: i32) -> Self { Self { width, height } } } fn main() { let width = 3; let height = 4; let rect1 = Rectangle::new(width, height); println!("{}", rect1::area()); //~^ ERROR failed to resolve: use of undeclared crate or module `rect1` }

Current output is:

error[E0433]: failed to resolve: use of undeclared crate or module `rect1` --> src/main.rs:27:20 | 27 | println!("{}", rect1::area()); | ^^^^^ use of undeclared crate or module `rect1` | help: `rect1` is not a crate or module, maybe you meant to call instance method | 27 | println!("{}", rect1.area()); | ~~~~~~ For more information about this error, try `rustc --explain E0433`.

You are right.
This need to delay the suggestion to be emit in type checking phase, I will have a try.

Spent some time to trying this, I think it's complicated to make it work. We need to find the local binding of and ty of the ident, then to check whether it has the method.

See my branch:
chenyukang@9cf2a60

Not sure whether worth it for a corner case of suggestion.

Adding a field to Resolver like the following for storing impl items might help you.

rust/compiler/rustc_resolve/src/lib.rs

Line 1026 in 4891d57

trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,

I continue with my previous solution, delay diagnostic to checking method in type checking phase, now it works by checking whether the method name is valid (may need more tweak about the arguments checking).

I have a question for my current code, how can we find the binding according to a ident(then find out the type of it),

My code for this part is:
https://github.com/rust-lang/rust/pull/101975/files#diff-8dea1c54efc225f1b3a27454cbf2fc50f016073f51319b27d1b834bee7c5419eR1435

It's a little bit complicated to use a visitor for this, another issue is it can only handle the let expression, I want our suggestion works also for other scenarios, such as the binding is introduced by function arguments.

@compiler-errors do you know any better solution for this?

bors · 2022-11-04T22:58:14Z

☔ The latest upstream changes (presumably #103978) made this pull request unmergeable. Please resolve the merge conflicts.

chenyukang · 2022-11-20T11:11:26Z

Hi @TaKO8Ki,
Any more suggestion on this PR?

bors · 2022-11-21T02:17:37Z

☔ The latest upstream changes (presumably #104655) made this pull request unmergeable. Please resolve the merge conflicts.

compiler/rustc_resolve/src/diagnostics.rs

compiler-errors · 2022-11-22T01:49:45Z

compiler/rustc_resolve/src/diagnostics.rs

+                        let Ok(snippet) = sm.span_to_snippet(span) &&
+                            snippet.starts_with("::") &&  snippet.matches("::").count() == 1 {
+                        let local_span = *self.pat_span_map.get(&local_id).unwrap();
+                        let mut err = self.session.struct_span_err(


Why are you making a new error here? Is it possible to pass this down to where the original error (use of undeclared crate or module) is being created?

This is because I need to stash it, and if the method checking failed, I want cancel it, but the previous one use of undeclared crate or module should always emit?

Yes, but there should not be two errors -- only one, and you can append a suggestion to it.

Let' me try to stash use of undeclared crate or module, and only add help suggestion when method checking succeed.

oops, seems need many more changes, since report_path_resolution_error only report the error message and suggestions.

Yeah, you probably need to pass it down in the return statement and use it where that error is being created.

maybe this function is not the proper position to add this check...😛

Maybe so... but I would prefer if we did it the correct way. Is it possible to investigate the correct way of doing it?

Yes, let me try it.

Code updated!
There are some test case result changed, since the diagnostic order change.

compiler/rustc_hir_typeck/src/method/suggest.rs

compiler-errors · 2022-11-22T01:52:27Z

compiler/rustc_hir_typeck/src/method/suggest.rs

+        let parent = self.tcx.hir().get_parent_node(seg1.hir_id);
+        if let Some(Node::Expr(call_expr)) = self.tcx.hir().find(parent) &&
+            let Some(expr) = visitor.result {
+            let self_ty = self.check_expr(expr);


This is checking an expression that should have already been checked. There should be a way of using the TypeckResults (or something else) to find the Ty of a local variable...

Use node_ty to get Ty now.

compiler/rustc_hir_typeck/src/method/suggest.rs

compiler-errors · 2022-11-22T01:55:28Z

Sorry for taking so long to review this even though I was cc'd. I gave this some reviews, let me know what you think @chenyukang. I like the idea of the diagnostic, though.

compiler-errors · 2022-11-22T06:51:42Z

r? @compiler-errors

compiler-errors · 2022-11-26T22:54:44Z

@chenyukang make sure to do:

@rustbot ready

When you're ready to review. Otherwise I might not see this, haha.

chenyukang · 2022-11-27T01:08:48Z

@compiler-errors thanks for reminder! 😁

compiler-errors · 2022-12-03T14:31:22Z

compiler/rustc_hir_typeck/src/method/suggest.rs

+                let sm = self.infcx.tcx.sess.source_map();
+                diag.span_suggestion_verbose(
+                    sm.span_extend_while(seg1.ident.span.shrink_to_hi(), |c| c == ':').unwrap(),
+                    "maybe you meant to call instance method",


Suggested change

"maybe you meant to call instance method",

"you may have meant to call an instance method",

compiler-errors

Thanks, this looks pretty good. I will give one last review once you fix the typo. Please ping me if I forget.

…an object

chenyukang · 2022-12-03T14:42:49Z

Thanks, this looks pretty good. I will give one last review once you fix the typo. Please ping me if I forget.

Updated, thanks!

compiler-errors · 2022-12-04T14:52:39Z

@bors r+

bors · 2022-12-04T14:52:41Z

📌 Commit fb004e9 has been approved by compiler-errors

It is now in the queue for this repository.

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#101975 (Suggest to use . instead of :: when accessing a method of an object) - rust-lang#105141 (Fix ICE on invalid variable declarations in macro calls) - rust-lang#105224 (Properly substitute inherent associated types.) - rust-lang#105236 (Add regression test for rust-lang#47814) - rust-lang#105247 (Use parent function WfCheckingContext to check RPITIT.) - rust-lang#105253 (Update a couple of rustbuild deps) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

bors · 2022-12-04T19:48:27Z

⌛ Testing commit fb004e9 with merge 0f0d5d7...

rust-highfive assigned TaKO8Ki Sep 18, 2022

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chenyukang force-pushed the fix-101749 branch from 2a3edb5 to fa83004 Compare December 3, 2022 14:37

fix rust-lang#101749, use . instead of :: when accessing a method of …

fb004e9

…an object

chenyukang force-pushed the fix-101749 branch from fa83004 to fb004e9 Compare December 3, 2022 14:41

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 4, 2022

matthiaskrgr mentioned this pull request Dec 4, 2022

Rollup of 6 pull requests #105261

Merged

bors merged commit 7dbd160 into rust-lang:master Dec 4, 2022

rustbot added this to the 1.67.0 milestone Dec 4, 2022

	"maybe you meant to call instance method",
	"you may have meant to call an instance method",

Suggest to use . instead of :: when accessing a method of an object #101975

Suggest to use . instead of :: when accessing a method of an object #101975

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chenyukang commented Sep 18, 2022 • edited Loading

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