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gccgo: couldn't detect method of unnamed types #38125

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dotaheor opened this issue Mar 28, 2020 · 5 comments
Closed

gccgo: couldn't detect method of unnamed types #38125

dotaheor opened this issue Mar 28, 2020 · 5 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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Gccgo

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@dotaheor
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dotaheor commented Mar 28, 2020 •
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What version of Go are you using (go version)?

$ gccgo --version
gccgo (Ubuntu 8.3.0-6) 8.3.0

Does this issue reproduce with the latest release?

True

What did you do?

package main

import (
	"fmt"
	"time"
)
	

type T = struct {
	time.Time
}

func main() {
	fmt.Println(T.Add)
	fmt.Printf("%T\n", struct {time.Time}.Add)
}

What did you expect to see?

Compile and run okay.

What did you see instead?

Not compile.

$ go run -compiler=gccgo main.go
# command-line-arguments
./main.go:14:15: error: type ‘T’ has no method ‘Add’
  fmt.Println(T.Add)
               ^
./main.go:15:39: error: method expression requires named type or pointer to named type
  fmt.Printf("%T\n", struct {time.Time}.Add)
@gopherbot gopherbot added this to the Gccgo milestone Mar 28, 2020
@dotaheor dotaheor mentioned this issue Mar 28, 2020
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@dotaheor
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Another finding:

package main

import (
	"fmt"
	"time"
	"reflect"
)
	
// For gccgo, it is strange that if this type alias declaration
// is removed, then the output is 35, otherwase, it is 0.
type T = struct {
	time.Time
}

func main() {
	var x struct {time.Time}
	var t = reflect.TypeOf(x)
	fmt.Println(t.NumMethod())
}

@andybons
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@dotaheor can you provide the error that you get when attempting to compile?

/cc @ianlancetaylor @thanm @cherrymui

@andybons andybons added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Mar 30, 2020
@dotaheor
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appended.

@gopherbot
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Change https://golang.org/cl/251168 mentions this issue: test: add test that gccgo failed to compile

@gopherbot
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Change https://golang.org/cl/251279 mentions this issue: compiler: finalize methods for type aliases of struct types

gopherbot pushed a commit that referenced this issue Aug 28, 2020
@ianlancetaylor
test: add test that gccgo failed to compile
49bae98 
For #38125

Change-Id: Id6ef10d74f0f9dbad2851531e0fe019cd145cf7c
Reviewed-on: https://go-review.googlesource.com/c/go/+/251168
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
jpf91 pushed a commit to D-Programming-GDC/gcc that referenced this issue Sep 22, 2020
@ianlancetaylor
compiler: finalize methods for type aliases of struct types
27edc6c 
Previously we would finalize the methods of the alias type itself, but
since its a type alias we really need to finalize the methods of the
aliased type.

Also, handle method expressions of unnamed struct types.

Test case is https://golang.org/cl/251168.

Fixes golang/go#38125

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/251279
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@andybons @gopherbot @dotaheor