Panic while testing github.com/mstone/focus/ot

[mstone]

I tried go-mutesting on an operational transformation algorithm I'm implementing (package github.com/mstone/focus/ot) and got this panic while running:

go-mutesting --exec "$GOPATH/src/github.com/zimmski/go-mutesting/scripts/simple.sh" github.com/mstone/focus/ot

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0x1 addr=0x0 pc=0x448bd5]

goroutine 16 [running]:
runtime.panic(0x5dd0c0, 0x71caf3)
    /usr/lib/go/src/pkg/runtime/panic.c:279 +0xf5
go/ast.(*Ident).Pos(0x0, 0x57f2c0)
    /usr/lib/go/src/pkg/go/ast/ast.go:423 +0x5
go/ast.(*BinaryExpr).Pos(0xc2080682d0, 0xc2080a4798)
    /usr/lib/go/src/pkg/go/ast/ast.go:441 +0x3f
go/printer.(*printer).binaryExpr(0xc20804e000, 0xc208068300, 0x0, 0x6, 0x1)
    /usr/lib/go/src/pkg/go/printer/nodes.go:647 +0x399
go/printer.(*printer).expr1(0xc20804e000, 0x7f46a38d5ae0, 0xc208068300, 0x0, 0x1)
    /usr/lib/go/src/pkg/go/printer/nodes.go:686 +0xf81
go/printer.(*printer).expr(0xc20804e000, 0x7f46a38d5ae0, 0xc208068300)
    /usr/lib/go/src/pkg/go/printer/nodes.go:893 +0x4d
go/printer.(*printer).controlClause(0xc20804e000, 0xc2080a4d00, 0x0, 0x0, 0x7f46a38d5ae0, 0xc208068300, 0x0, 0x0)
    /usr/lib/go/src/pkg/go/printer/nodes.go:996 +0x12c
go/printer.(*printer).stmt(0xc20804e000, 0x7f46a38d5b18, 0xc20806e3c0, 0x100)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1151 +0x29f2
    /usr/lib/go/src/pkg/go/printer/nodes.go:942 +0xfe
go/printer.(*printer).adjBlock(0xc20804e000, 0x33, 0xb, 0xc208068510)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1514 +0x683
go/printer.(*printer).funcDecl(0xc20804e000, 0xc208068540)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1538 +0x2b5
go/printer.(*printer).decl(0xc20804e000, 0x7f46a38d59c8, 0xc208068540)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1548 +0xa4
go/printer.(*printer).declList(0xc20804e000, 0xc20804a400, 0x13, 0x20)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1589 +0x1b0
go/printer.(*printer).file(0xc20804e000, 0xc20804c500)
    /usr/lib/go/src/pkg/go/printer/nodes.go:1597 +0x18b
go/printer.(*printer).printNode(0xc20804e000, 0x5ce020, 0xc20804c500, 0x0, 0x0)
    /usr/lib/go/src/pkg/go/printer/printer.go:1087 +0x8b2
go/printer.(*Config).fprint(0xc2080a57d8, 0x7f46a38d6170, 0xc208088060, 0xc20800e040, 0x5ce020, 0xc20804c500, 0xc208068150, 0x0, 0x0)
    /usr/lib/go/src/pkg/go/printer/printer.go:1226 +0xad
go/printer.(*Config).Fprint(0xc2080a57d8, 0x7f46a38d6170, 0xc208088060, 0xc20800e040, 0x5ce020, 0xc20804c500, 0x0, 0x0)
    /usr/lib/go/src/pkg/go/printer/printer.go:1284 +0x96
go/printer.Fprint(0x7f46a38d6170, 0xc208088060, 0xc20800e040, 0x5ce020, 0xc20804c500, 0x0, 0x0)
    /usr/lib/go/src/pkg/go/printer/printer.go:1291 +0xb0
main.saveAST(0xc208024720, 0xc2080b00c0, 0x57, 0xc20800e040, 0x7f46a38d5ba0, 0xc20804c500, 0x0, 0x0, 0xc208024500, 0x0, ...)
    /home/mistone/go/src/github.com/zimmski/go-mutesting/cmd/go-mutesting/main.go:396 +0x202
main.mainCmd(0xc20800e010, 0x3, 0x3, 0xa)
    /home/mistone/go/src/github.com/zimmski/go-mutesting/cmd/go-mutesting/main.go:257 +0x1dfc
main.main()
    /home/mistone/go/src/github.com/zimmski/go-mutesting/cmd/go-mutesting/main.go:352 +0x69

goroutine 19 [finalizer wait]:
runtime.park(0x417dc0, 0x721070, 0x71fb89)
    /usr/lib/go/src/pkg/runtime/proc.c:1369 +0x89
runtime.parkunlock(0x721070, 0x71fb89)
    /usr/lib/go/src/pkg/runtime/proc.c:1385 +0x3b
runfinq()
    /usr/lib/go/src/pkg/runtime/mgc0.c:2644 +0xcf
runtime.goexit()
    /usr/lib/go/src/pkg/runtime/proc.c:1445

goroutine 22 [chan receive]:
github.com/zimmski/go-mutesting/mutator/expression.(*MutatorRemoveTerm).Mutate(0x721570, 0x7f46a38d60a8, 0xc2080682d0, 0xc2080b0240)
    /home/mistone/go/src/github.com/zimmski/go-mutesting/mutator/expression/remove.go:76 +0x1b6
github.com/zimmski/go-mutesting.(*mutateWalk).Visit(0xc2080b6020, 0x7f46a38d60a8, 0xc2080682d0, 0x0, 0x0)
    /home/mistone/go/src/github.com/zimmski/go-mutesting/walk.go:71 +0x115
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d60a8, 0xc2080682d0)
    /usr/lib/go/src/pkg/go/ast/walk.go:52 +0x58
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d60a8, 0xc208068300)
    /usr/lib/go/src/pkg/go/ast/walk.go:147 +0x1ead
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d6078, 0xc20806e3c0)
    /usr/lib/go/src/pkg/go/ast/walk.go:230 +0x43bc
go/ast.walkStmtList(0x7f46a38d5bd0, 0xc2080b6020, 0xc20806e580, 0x3, 0x4)
    /usr/lib/go/src/pkg/go/ast/walk.go:32 +0xd1
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d5ec8, 0xc208068510)
    /usr/lib/go/src/pkg/go/ast/walk.go:224 +0x41e7
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d5e68, 0xc208068540)
    /usr/lib/go/src/pkg/go/ast/walk.go:342 +0xccb
go/ast.walkDeclList(0x7f46a38d5bd0, 0xc2080b6020, 0xc20804a400, 0x13, 0x20)
    /usr/lib/go/src/pkg/go/ast/walk.go:38 +0xd1
go/ast.Walk(0x7f46a38d5bd0, 0xc2080b6020, 0x7f46a38d5ba0, 0xc20804c500)
    /usr/lib/go/src/pkg/go/ast/walk.go:351 +0x2cb6
github.com/zimmski/go-mutesting.func·001()
    /home/mistone/go/src/github.com/zimmski/go-mutesting/walk.go:51 +0x71
created by github.com/zimmski/go-mutesting.MutateWalk
    /home/mistone/go/src/github.com/zimmski/go-mutesting/walk.go:54 +0xdb

[mstone]

(NB: this is with

$ go version
go version go1.3.2 linux/amd64

and with go-mutesting from 9572a4a.)

Also, running with --debug and --verbose does not give any obvious clues as to the nature of the problem. :-/

[zimmski]

I can reproduce it with "go1.4 linux/amd64"

[zimmski]

@mstone can you test if the newest revision b4485d5 fixes the problem for you?

[mstone]

Seems fixed, thanks!

(And of course, thank you for the cool testing software!)

[zimmski]

I am glad that you find it useful :-) There is stil a lot what could be done so please do not hesitate to open issues if you have any ideas. I am thinking of adding some additional mutators for switches and constant values but I am a little swamped right now.
Happy new year btw ^^