[SR-3254] Unhelpful diagnostics for compound name reference.

[rintaro]

Previous ID	SR-3254
Radar	None
Original Reporter	@rintaro
Type	Bug

Environment

Swift version 3.0.1 (swift-3.0.1-RELEASE)
Target: x86_64-unknown-linux-gnu

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, StarterBug
Assignee	None
Priority	Medium

md5: fcfded4004226fb4776f82d7b6864fca

relates to:

• SR-4867 func foo() {}; foo(_:) // Use of unresolved identifier 'foo'

Issue Description:

func foo(x: Int) {}
let f = foo(_:)

emits:

test.swift:2:9: error: use of unresolved identifier 'foo'
let f = foo(_:)
        ^~~~~~~
test.swift:1:6: note: did you mean 'foo'?
func foo(x: Int) {}
     ^

Because foo does exist. It should be something like:

test.swift:2:9: error: use of unresolved name 'foo(_:)'
let f = foo(_:)
        ^~~~~~~
test.swift:1:6: note: did you mean 'foo(x:)'?
func foo(x: Int) {}
     ^

[swift-ci]

Comment by Oscar Swanros (JIRA)

I'm trying to modify the DiagnosticsSema.def file for diag::note_typo_candidate to make it accept a DeclName instead of a StringRef so it can print the whole name as the suggestion.

However, after the change, the InFlightDiagnostic forwarding template for DiagnosticEngine is not accepting DeclName as a valid argument for any of the diagnose methods.

What else needs to be changed? @modocache CodaFi (JIRA User)

[modocache]

I'm not sure. Looking at the various specializations of InFlightDiagnostic::diagnose declared in include/swift/AST/DiagnosticEngine.h, it seems like it declares methods that take an ArrayRef<DiagnosticArgument>, and DiagnosticArgument in turn defines initializes that take a a single DeclName parameter. Based on my (very tenuous) grasp of C++, this seems like it'd work.

Can you post the compilation errors you're seeing? "Not accepting" is a little too vague for me to provide many more ideas.

[swift-ci]

Comment by Oscar Swanros (JIRA)

The specific error after changing the diag::note_typo_candidate note is a semantic issue: No matching member function for call to 'diagnose', at TypeChecker.h line 715.

[modocache]

If you could post the full output from your compilation to https://gist.github.com, that might make this easier. 🙂

My understanding is that what we're looking at here is that some class, probably DiagnosticEngine or InFlightDiagnostic or something, that doesn't have a diagnose method defined that responds to the arguments you're passing it. There are a bunch of methods named diagnose, however, so it's a little hard for me to tell just by reading the code which one is complaining... the full output from your compilation would help track it down!

[swift-ci]

Comment by Oscar Swanros (JIRA)

Ok, I figured it out.

Turns out that the issue was that there were other calls to diagnose with diag::note_typo_candidate as a parameter that were not passing the updated DeclName value, but a StringRef value still. Updating those calls to also pass a DeclName solved that issue.

[modocache]

Awesome! Keep posting any questions you have. Hopefully they help you reason about the failures as much as they help me learn about different parts of the Swift codebase. 🙂

[swift-ci]

Comment by Oscar Swanros (JIRA)

I've submitted an initial PR for this, awaiting general comments. Hopefully this is helpful!

#6715

[modocache]

Great work!

[belkadan]

Resetting assignee for all Starter Bugs not modified since 2018. If anyone wants to pick up swanros (JIRA User)'s PR they're welcome to!