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go/parser: bad error message for a badly formed func literal #36750

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myitcv opened this issue Jan 24, 2020 · 4 comments
Open

go/parser: bad error message for a badly formed func literal #36750

myitcv opened this issue Jan 24, 2020 · 4 comments
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NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Unreleased

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@myitcv
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myitcv commented Jan 24, 2020

What version of Go are you using (go version)?

$ go version
go version devel +8e0be05ec7 Sun Jan 19 14:04:09 2020 +0000 linux/amd64
$ go list -m golang.org/x/tools
golang.org/x/tools v0.0.0-20200121200311-d456b1cd8c86
$ go list -m golang.org/x/tools/gopls
golang.org/x/tools/gopls v0.1.8-0.20200121200311-d456b1cd8c86

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myitcv/.cache/go-build"
GOENV="/home/myitcv/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/myitcv/gostuff"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/myitcv/gos"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/myitcv/.vim/plugged/govim/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build878422207=/tmp/go-build -gno-record-gcc-switches"

What did you do?

The diagnostic for the following file is misleading:

package main

func main() {
	_ = func(format string, args ...interface) error {
		return nil
	}
}

We get:

PublishDiagnostics callback: &protocol.PublishDiagnosticsParams{
    URI:         "file:///home/myitcv/gostuff/src/github.com/myitcv/playground/main.go",
    Version:     36,
    Diagnostics: {
        {
            Range: protocol.Range{
                Start: protocol.Position{Line:3, Character:5},
                End:   protocol.Position{Line:3, Character:5},
            },
            Severity:           1,
            Code:               nil,
            Source:             "syntax",
            Message:            "expected expression",
            Tags:               nil,
            RelatedInformation: nil,
        },
    },
}

Contrast what we get from the compiler:

./main.go:4:43: syntax error: unexpected ), expecting {
./main.go:5:3: syntax error: unexpected return, expecting comma or )
./main.go:7:1: syntax error: non-declaration statement outside function body

What did you expect to see?

A better diagnostic.

What did you see instead?

Per above

Marking as gopls/v1.0.0 because this isn't critical for v0.3.0.

cc @stamblerre

FYI @leitzler
@myitcv myitcv added NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. gopls Issues related to the Go language server, gopls. labels Jan 24, 2020
@myitcv myitcv added this to the gopls/v1.0.0 milestone Jan 24, 2020
@gopherbot gopherbot added the Tools This label describes issues relating to any tools in the x/tools repository. label Jan 24, 2020
@heschi
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heschi commented Jan 24, 2020

This would be coming from go/parser or something, no? I don't think gopls can do anything to improve it.

@stamblerre
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Yes, this is is coming from go/parser. A minimal repro can be found here: https://play.golang.org/p/ca24wvyr5Wl. This seems like an instance where go/parser's errors should be updated to match the compiler's. I'll change the issue title to reflect this.

@stamblerre stamblerre changed the title x/tools/gopls: misleading diagnostic for badly formed func literal go/parser: bad error message for a badly formed func literal Mar 12, 2020
@stamblerre stamblerre removed NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. Tools This label describes issues relating to any tools in the x/tools repository. gopls Issues related to the Go language server, gopls. labels Mar 12, 2020
@stamblerre stamblerre modified the milestones: gopls/v1.0.0, Unreleased Mar 12, 2020
@toothrot toothrot added the NeedsFix The path to resolution is known, but the work has not been done. label Mar 12, 2020
@toothrot
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/cc @griesemer

@gopherbot
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Change https://golang.org/cl/259817 mentions this issue: go/parser: Improve error message to user when interface parsing fails

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@toothrot @myitcv @stamblerre @gopherbot @heschi