code review 6448097: cmd/gc: Don't claim type assertion would help when it wont.

cmd/gc: Don't claim type assertion would help when it wont.

Fixes issue 3465.

[DMorsing, 2012-08-01 16:31:56]

Hello golang-dev@googlegroups.com (cc: golang-dev@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[rsc, 2012-08-03 19:15:22]

Looks good but please add a test case.
interface/*.go is probably a good place to drop it.

Russ

[DMorsing, 2012-08-03 20:25:31]

PTAL

[remyoudompheng, 2012-08-03 20:28:43]

http://codereview.appspot.com/6448097/diff/2003/test/interface/explicit.go
File test/interface/explicit.go (right):

http://codereview.appspot.com/6448097/diff/2003/test/interface/explicit.go#ne...
test/interface/explicit.go:43: t = i // ERROR "assignment$"
i suppose the "incompatible" part was there for gccgo test suite.

[DMorsing, 2012-08-05 14:42:47]

On 2012/08/03 20:28:43, remyoudompheng wrote:
> http://codereview.appspot.com/6448097/diff/2003/test/interface/explicit.go
> File test/interface/explicit.go (right):
> 
>
http://codereview.appspot.com/6448097/diff/2003/test/interface/explicit.go#ne...
> test/interface/explicit.go:43: t = i // ERROR "assignment$"
> i suppose the "incompatible" part was there for gccgo test suite.

I'm not sure how to test this on both gccgo and gc without the test being a bit
fragile. If gc is changed to emit a phrase similar to gccgo, the test will
succeed even if gc starts claiming that a type assertion will fix the problem.

[iant, 2012-08-05 17:14:08]

On 2012/08/05 14:42:47, DMorsing wrote:
> 
> I'm not sure how to test this on both gccgo and gc without the test being a
bit
> fragile. If gc is changed to emit a phrase similar to gccgo, the test will
> succeed even if gc starts claiming that a type assertion will fix the problem.

For an errorcheck test, the error matches are regexps.  So it's typical to use
'|' to separate matches for gc and matches for gccgo.  In this case the gccgo
output for the test is


interface/explicit.go:37: error: incompatible types in assignment (need explicit
conversion)
interface/explicit.go:42: error: incompatible types in assignment (type has no
methods)
interface/explicit.go:43: error: incompatible types in assignment (need explicit
conversion)
interface/explicit.go:46: error: incompatible types in assignment (need explicit
conversion; missing method ‘N’)
interface/explicit.go:49: error: invalid type conversion (need explicit
conversion; missing method ‘N’)
interface/explicit.go:52: error: incompatible types in assignment
interface/explicit.go:52: error: invalid type conversion (need explicit
conversion)
interface/explicit.go:61: error: impossible type assertion: type does not
implement interface (type has no methods)
interface/explicit.go:67: error: impossible type assertion: type does not
implement interface (incompatible type for method ‘M’ (different number of
parameters))
interface/explicit.go:72: error: incompatible type in initialization (type has
no methods)
interface/explicit.go:73: error: incompatible type in initialization
(incompatible type for method ‘M’ (different number of parameters))
interface/explicit.go:75: error: invalid type conversion (type has no methods)
interface/explicit.go:76: error: invalid type conversion (incompatible type for
method ‘M’ (different number of parameters))

so that is what you have to match.  Basically, don't remove the "incompatible|"
from the match.

[DMorsing, 2012-08-05 18:24:47]

Hello golang-dev@googlegroups.com, rsc@golang.org, remyoudompheng@gmail.com,
iant@golang.org (cc: golang-dev@googlegroups.com),

Please take another look.

[DMorsing, 2012-08-15 13:23:12]

ping?

[iant, 2012-08-15 23:52:40]

LGTM

[iant, 2012-08-15 23:53:10]

*** Submitted as http://code.google.com/p/go/source/detail?r=b76339cc168a ***

cmd/gc: Don't claim type assertion would help when it wont.

Fixes issue 3465.

R=golang-dev, rsc, remyoudompheng, iant
CC=golang-dev
http://codereview.appspot.com/6448097

Committer: Ian Lance Taylor <iant@golang.org>