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cmd/gc: _ methods in interfaces causes internal compiler error #5691

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griesemer opened this issue Jun 12, 2013 · 6 comments
Closed

cmd/gc: _ methods in interfaces causes internal compiler error #5691

griesemer opened this issue Jun 12, 2013 · 6 comments
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Go1.2

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@griesemer
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What steps will reproduce the problem?
http://play.golang.org/p/uW1VPvis0M

What is the expected output? What do you see instead?

The spec does not disallow blank (_) methods, and it's possible to declare them for
non-interface types, so this package should compile w/o errors.

However, 6g produces:

prog.go:1: cannot refer to blank field or method
prog.go:1: internal compiler error: orderstmt function call

gccgo accepts this code w/o problems.
@ality
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ality commented Jun 12, 2013

Comment 1:

The easy fix is to not call genwrapper for _ method symbols but I wonder
what the semantics should be for http://play.golang.org/p/dhbX0y1u9O
gccgo gives:
a.go:16:4: error: incompatible types in assignment (missing method ‘_’)
  i = &T{}
    ^
Should blank methods simply be ignored?

@griesemer
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Comment 2:

gccgo complains with the same error:
x.go:16:8: error: incompatible types in assignment (missing method '_')
      i = &T{}
        ^
I believe that it is legal to define as many _ methods as one wants (in interfaces and
for other types), but that they are not visible. Thus, no type can ever satisfy an
interface with a _ method.
But the spec doesn't help much in this respect.

@rsc
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rsc commented Jun 12, 2013

Comment 3:

I agree with gri.

@ality
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ality commented Jun 14, 2013

Comment 4:

This fix is here: https://golang.org/cl/10255047/

Labels changed: added compilerbug, removed priority-triage.

Owner changed to @ality.

Status changed to Started.

@rsc
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rsc commented Jul 30, 2013

Comment 5:

Labels changed: added go1.2.

@ality
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ality commented Aug 19, 2013

Comment 6:

This issue was closed by revision f316a7e.

Status changed to Fixed.

@rsc rsc added this to the Go1.2 milestone Apr 14, 2015
@rsc rsc removed the go1.2 label Apr 14, 2015
@golang golang locked and limited conversation to collaborators Jun 24, 2016
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@rsc @ality @griesemer @gopherbot