Make suggestions for 'does not implement any method in scope'

[aidanhs]

I made this mistake just now:

~/rust/tclscan $ cargo test
   Compiling tclscan v0.0.1 (file:///home/ahobsons/rust/tclscan)
/home/ahobsons/rust/tclscan/src/lib.rs:120:59: 120:72 error: type `collections::vec::Vec<&str>` does not implement any method in scope named `connnect`
/home/ahobsons/rust/tclscan/src/lib.rs:120             Ok(true) => println!("DANGER: {}", token_strs.connnect(' ')),
                                                                                                     ^~~~~~~~~~~~~
error: aborting due to previous error
Build failed, waiting for other jobs to finish...
/home/ahobsons/rust/tclscan/src/lib.rs:120:59: 120:72 error: type `collections::vec::Vec<&str>` does not implement any method in scope named `connnect`
/home/ahobsons/rust/tclscan/src/lib.rs:120             Ok(true) => println!("DANGER: {}", token_strs.connnect(' ')),
                                                                                                     ^~~~~~~~~~~~~
error: aborting due to previous error
Could not compile `tclscan`.

To learn more, run the command again with --verbose.

(count the 'n's)

It'd be nice if this made the suggestion for 'connect' (like misspelling a variable does).
I had a look but can't see any existing issues for this.

[kmcallister]

This sounds more useful than the existing suggestion for variable names. Also, both of them should probably have a maximum edit distance threshold -- the hilariously wrong suggestions we get today decrease the utility of the feature as a whole.

[fitzgen]

I'm working on a patch for this.

[fitzgen]

Edit distance by itself isn't the best metric. For example, an edit distance of 3 is often huge: "wutang" -> "mutate" is an edit distance of 3. However, this edit-distance-3 mismatch is fairly common: "foobar" instead of "getFoobar".

However, I will start with simply making the existing infrastructure work with methods.

[fitzgen]

Edit distance by itself isn't the best metric. For example, an edit distance of 3 is often huge: "wutang" -> "mutate" is an edit distance of 3. However, this edit-distance-3 mismatch is fairly common: "foobar" instead of "getFoobar".

FWIW, clang handles this stuff really well, so it would probably be insightful to see what their heuristics are.

[fitzgen]

I can't figure out exactly where function names live. When resolving functions, it pushes to value_ribs and label_ribs, but the given FnDecl doesn't seem to have access to the function's name. Also, looked into the def_map but I think that isn't ordered by scope.

Would appreciate some pointers, thanks.

[brson]

As far as I can tell we still don't give suggestions for misspelled method names: https://is.gd/oR7fI6. This is presumably relatively easy to do, but this bug doesn't indicate how. @rust-lang/compiler can anybody give pointers on how to set up spell-check on methods and tag this E-easy again?

[Mark-Simulacrum]

This is basically #30197, closing in favor of that.