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x/tools/gopls: report error only at function signature for incompatible function literals #72977

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danvolchek opened this issue Mar 20, 2025 · 2 comments
Open

x/tools/gopls: report error only at function signature for incompatible function literals #72977

danvolchek opened this issue Mar 20, 2025 · 2 comments
Labels
gopls Issues related to the Go language server, gopls. Tools This label describes issues relating to any tools in the x/tools repository.
Milestone
Unreleased

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@danvolchek
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danvolchek commented Mar 20, 2025 •
edited
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gopls version

Build info
----------
golang.org/x/tools/gopls v0.18.1
    golang.org/x/tools/gopls@v0.18.1 h1:2xJBNzdImS5u/kV/ZzqDLSvlBSeZX+pWY9uKVP7Pask=
    github.com/BurntSushi/toml@v1.4.1-0.20240526193622-a339e1f7089c h1:pxW6RcqyfI9/kWtOwnv/G+AzdKuy2ZrqINhenH4HyNs=
    github.com/google/go-cmp@v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
    golang.org/x/exp/typeparams@v0.0.0-20241210194714-1829a127f884 h1:1xaZTydL5Gsg78QharTwKfA9FY9CZ1VQj6D/AZEvHR0=
    golang.org/x/mod@v0.23.0 h1:Zb7khfcRGKk+kqfxFaP5tZqCnDZMjC5VtUBs87Hr6QM=
    golang.org/x/sync@v0.11.0 h1:GGz8+XQP4FvTTrjZPzNKTMFtSXH80RAzG+5ghFPgK9w=
    golang.org/x/telemetry@v0.0.0-20241220003058-cc96b6e0d3d9 h1:L2k9GUV2TpQKVRGMjN94qfUMgUwOFimSQ6gipyJIjKw=
    golang.org/x/text@v0.22.0 h1:bofq7m3/HAFvbF51jz3Q9wLg3jkvSPuiZu/pD1XwgtM=
    golang.org/x/tools@v0.30.1-0.20250221230316-5055f70f240c h1:Ja/5gV5a9Vvho3p2NC/T2TtxhHjrWS/2DvCKMvA0a+Y=
    golang.org/x/vuln@v1.1.3 h1:NPGnvPOTgnjBc9HTaUx+nj+EaUYxl5SJOWqaDYGaFYw=
    honnef.co/go/tools@v0.5.1 h1:4bH5o3b5ZULQ4UrBmP+63W9r7qIkqJClEA9ko5YKx+I=
    mvdan.cc/gofumpt@v0.7.0 h1:bg91ttqXmi9y2xawvkuMXyvAA/1ZGJqYAEGjXuP0JXU=
    mvdan.cc/xurls/v2@v2.5.0 h1:lyBNOm8Wo71UknhUs4QTFUNNMyxy2JEIaKKo0RWOh+8=
go: go1.24.0

go env

Env info 
AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/dan/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/dan/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build2088853875=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/dan/Desktop/Stuff/development/go-rw2/go.mod'
GOMODCACHE='/home/dan/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/dan/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/dan/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/go/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.24.1'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

In vscode, passed a function literal with an incompatible signature as an argument to another function, i.e.

package main


func foo(fooer func(int)) {
	// ...
}

func main() {
	foo(func(bool) {
	  // ...
	})
}

here, foo expects func(int) but it gets func(bool).

What did you see happen?

The entire function literal (signature and body) is underlined with red squiggles. The problem is with the signature, but the red squiggles over the entire body make it hard to see where the problem actually is.

I.e.

Image

What did you expect to see?

This is a feature request - it would be nice if only the signature is underlined as the problem.

I.e.

Image

Editor and settings

    "gopls": {
        "ui.diagnostic.staticcheck": true
    },
    "[go]": {
        "editor.formatOnSave": true
    },
    "go.toolsManagement.autoUpdate": true,

Logs

No response
@danvolchek danvolchek added gopls Issues related to the Go language server, gopls. Tools This label describes issues relating to any tools in the x/tools repository. labels Mar 20, 2025
@gopherbot gopherbot added this to the Unreleased milestone Mar 20, 2025
@adonovan
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adonovan commented Mar 21, 2025 •
edited
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For this input

package main


func foo(fooer func(int)) {
	// ...
}

func main() {
	foo(‸₀func(bool) {
	  // ...
	}‸₁)
}

the type checker reports a types.Error of this form:

types.Error{
	Pos: ‸₀,
	Msg: "cannot use (func(bool) literal) (value of type func(bool)) as func(int) value in argument to foo", 
	go116code: 23,
	go116start:‸₀,
	go116end:‸₁,
}

(I have replaced positions by numbered markers: ‸₀, etc.)

So the question is: should the type checker associate a smaller start/end range with this error, or should gopls post-process the syntax node enclosing that range, perhaps with special cases for FuncLit and other forms that are typically multiline? I would start with the type checker.

@griesemer @findleyr

@findleyr
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We should shorten this in go/types to the function signature.

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Labels
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