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bug: nil variable definition causes compiler panic #883

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paralin opened this issue Nov 28, 2018 · 6 comments
Open

bug: nil variable definition causes compiler panic #883

paralin opened this issue Nov 28, 2018 · 6 comments

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@paralin
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paralin commented Nov 28, 2018

Add the following line to the bottom of a Go file:

var _ context.Context = nil

This causes a Go compiler error.

Full compiler output and reproduce here:

https://gist.github.com/paralin/ef8a9b472baa6ecedfc708679a0f308c
@myitcv
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myitcv commented Dec 2, 2018

I can't reproduce this:

$ export GOPATH=$(mktemp -d)
$ export PATH=$GOPATH/bin:$PATH
$ cd $GOPATH
$ go get -u github.com/gopherjs/gopherjs
$ pushd $(go list -f "{{.Dir}}" github.com/gopherjs/gopherjs)
/tmp/tmp.5LNEgdudzf/src/github.com/gopherjs/gopherjs /tmp/tmp.5LNEgdudzf
$ git checkout d547d1d9531ed93dbdebcbff7f83e7c876a1e0ee
HEAD is now at d547d1d... CI: Update to Go 1.11.2. (#878)
$ go install
$ popd
/tmp/tmp.5LNEgdudzf
$ mkdir -p src/example.com/blah
$ cd src/example.com/blah
$ cat <<EOD >blah.go
package nilref

import (
        "context"
)

var _ context.Context = nil
EOD
$ gopherjs test
?       example.com/blah        [no test files]

Do you have a repro?

@paralin
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paralin commented Dec 6, 2018 •
edited
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@myitcv Check your little reproduction script, at the end you ran "gopherjs test" and got a "no test files" message. you did not actually compile the code. Try "gopherjs build -v ."

panic: unexpected basic type

@myitcv
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myitcv commented Dec 6, 2018

@paralin - doh! Thanks for spotting the obvious error. Here is the repro:

$ export GOPATH=$(mktemp -d)
$ export PATH=$GOPATH/bin:$PATH
$ cd $GOPATH
$ go get -u github.com/gopherjs/gopherjs
$ pushd $(go list -f "{{.Dir}}" github.com/gopherjs/gopherjs)
/tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs /tmp/tmp.YgplR3yGUf
$ git checkout d547d1d9531ed93dbdebcbff7f83e7c876a1e0ee
HEAD is now at d547d1d... CI: Update to Go 1.11.2. (#878)
$ go install
$ popd
/tmp/tmp.YgplR3yGUf
$ mkdir -p src/example.com/blah
$ cd src/example.com/blah
$ cat <<EOD >blah.go
package nilref

import (
        "context"
)

var _ context.Context = nil
EOD
$ gopherjs build
panic: unexpected basic type

goroutine 1 [running]:
github.com/gopherjs/gopherjs/compiler.(*funcContext).translateExpr(0xc0000df340, 0xa728e0, 0xc00088ae80, 0xc0008ae6e0)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/expressions.go:739 +0x11fa0
github.com/gopherjs/gopherjs/compiler.(*funcContext).translateStmt(0xc0000df340, 0xa722e0, 0xc0013abb80, 0x0)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/statements.go:359 +0x7643
github.com/gopherjs/gopherjs/compiler.Compile.func6.1()
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/package.go:341 +0x102
github.com/gopherjs/gopherjs/compiler.(*funcContext).CatchOutput(0xc0000df340, 0x1, 0xc0015e6ba0, 0x0, 0xc000080700, 0x110)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/utils.go:67 +0x87
github.com/gopherjs/gopherjs/compiler.Compile.func6()
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/package.go:340 +0xdb
github.com/gopherjs/gopherjs/compiler.Compile.func4(0xc0013abb40, 0xc0013abb40, 0xc001871360, 0xc0015e7468)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/package.go:291 +0x76
github.com/gopherjs/gopherjs/compiler.Compile(0xc0001a62b8, 0x10, 0xc00016d8f0, 0x1, 0x1, 0xc0013ab3c0, 0xc000512170, 0x0, 0x0, 0x0, ...)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/compiler/package.go:338 +0x2388
github.com/gopherjs/gopherjs/build.(*Session).BuildPackage(0xc00017c990, 0xc0001bc190, 0x0, 0x0, 0x0)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/build/build.go:706 +0x5c6
main.main.func1.1(0xdf5d40, 0x0, 0x0, 0xc0001800e0, 0xc00017c990, 0xc000168200, 0x88cf60, 0xc0000cbba8)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/tool.go:139 +0x70a
main.main.func1(0xc0001b2000, 0xdf5d40, 0x0, 0x0)
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/tool.go:155 +0xda
github.com/spf13/cobra.(*Command).execute(0xc0001b2000, 0xdf5d40, 0x0, 0x0, 0xc0001b2000, 0xdf5d40)
        /tmp/tmp.YgplR3yGUf/src/github.com/spf13/cobra/command.go:766 +0x2cc
github.com/spf13/cobra.(*Command).ExecuteC(0xc0001b3400, 0x8, 0x7, 0xc0001b2500)
        /tmp/tmp.YgplR3yGUf/src/github.com/spf13/cobra/command.go:852 +0x2fd
github.com/spf13/cobra.(*Command).Execute(0xc0001b3400, 0xc0000cbf48, 0x8)
        /tmp/tmp.YgplR3yGUf/src/github.com/spf13/cobra/command.go:800 +0x2b
main.main()
        /tmp/tmp.YgplR3yGUf/src/github.com/gopherjs/gopherjs/tool.go:534 +0x119c

@paralin
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paralin commented Dec 6, 2018

That's the one!

myitcv added a commit to myitcv/gopherjs that referenced this issue Dec 6, 2018
@myitcv
compiler: fix handling of nil assigned to blank identifier
7692e46 
Fixes gopherjs#883
@myitcv myitcv mentioned this issue Dec 6, 2018
Merged
myitcv added a commit to myitcv/gopherjs that referenced this issue Dec 6, 2018
@myitcv
compiler: fix handling of nil assigned to blank identifier (#38)
f5b96be 
Fixes gopherjs#883
@myitcv
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myitcv commented Dec 6, 2018

@paralin I have a fix for this in myitcv#38 (for some reason that closed this issue which I am re-opening).

Per #855 (comment) that fork will be merged back into the main repo at some point hopefully soon.

@myitcv myitcv reopened this Dec 6, 2018
@myitcv
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myitcv commented Dec 6, 2018

Also to note, per @paralin's observation above, there is a difference in behaviour between go test and gopherjs test when there are no test files (which is what lead to the above sequence of events). This is captured in myitcv#39 (which currently fails CI, pending the fix):

$ go test -run="TestScripts/test_no_tests"
--- FAIL: TestScripts (0.04s)
    --- FAIL: TestScripts/test_no_tests (0.33s)
        testscript.go:228:
            # go (0.067s)
            # gopherjs (0.189s)
            > ! gopherjs test
            [stdout]
            ?           mod     [no test files]
            FAIL: testdata/test_no_tests.txt:12: unexpected command success

FAIL
exit status 1
FAIL    github.com/gopherjs/gopherjs    0.411s

@myitcv myitcv mentioned this issue Dec 6, 2018
Open
@myitcv myitcv mentioned this issue Feb 20, 2019
Closed
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@paralin @myitcv