go/types, types2: gopls crash in computeInterfaceTypeSet with "duplicate method"

[wushilin]

gopls version: v0.8.0-pre.2
gopls flags:
update flags: proxy
extension version: 2022.2.1423
go version: 1.18beta2
environment: Visual Studio Code darwin
initialization error: undefined
issue timestamp: Sun, 20 Feb 2022 01:22:52 GMT
restart history:
Sun, 20 Feb 2022 00:43:53 GMT: activation (enabled: true)

ATTENTION: PLEASE PROVIDE THE DETAILS REQUESTED BELOW.

Describe what you observed.

panic: 2229938: duplicate method Contains

goroutine 995 [running]:
go/types.(*Checker).handleBailout(0xc002f50000, 0xc00179d650)
	  check.go:304  0x8b
panic({0x186bf00, 0xc001e97990})
	  panic.go:838  0x207
go/types.computeInterfaceTypeSet.func2(0x2206b2, 0xc002622280, 0x1)
	  typeset.go:233  0x5bd
go/types.computeInterfaceTypeSet(0x0, 0x18cbec0%3F, 0xc0020170e0)
	  typeset.go:260  0x2d5
go/types.(*Interface).typeSet(...)
	  interface.go:29
go/types.(*Interface).Empty(0x1bf2dc0%3F)
	  interface.go:111  0x25
go/types.(*Checker).implements(0xc002f50000, {0x1bf2de8%3F, 0xc001e97590}, {0x1bf2dc0%3F, 0xc000543730})
	  instantiate.go:187  0x485
go/types.(*operand).assignableTo(0xc002a98600, 0xc002f50000, {0x1bf2dc0%3F, 0xc000543730%3F}, 0xc00179bbf0)
	  operand.go:283  0x9c5
go/types.(*Checker).assignment(0xc002f50000, 0xc002a98600, {0x1bf2dc0, 0xc000543730}, {0xc0010e0e70, 0x18})
	  assignments.go:87  0x80b
go/types.(*Checker).arguments(0xc002f50000, 0xc001f05dc0, 0xc002a985c0, {0x0, 0x0, 0x0}, {0xc001f864a0%3F, 0x1, 0x1}, {0x0, ...})
	  call.go:414  0xbf4
go/types.(*Checker).callExpr(0xc002f50000, 0xc002a98500, 0xc001f05dc0)
	  call.go:210  0x669
go/types.(*Checker).exprInternal(0xc002f50000, 0xc002a98500, {0x1bf4e30%3F, 0xc001f05dc0}, {0x0%3F, 0x0%3F})
	  expr.go:1483  0x9f2
go/types.(*Checker).rawExpr(0xc002f50000%3F, 0x1bf0f20%3F, {0x1bf4e30%3F, 0xc001f05dc0%3F}, {0x0%3F, 0x0%3F}, 0x0)
	  expr.go:1111  0x45
go/types.(*Checker).stmt(0xc002f50000, 0x0, {0x1bf4fe0%3F, 0xc00229dec0%3F})
	  stmt.go:394  0x247c
go/types.(*Checker).stmtList(0xc002f50000%3F, 0x0, {0xc0007e6400%3F, 0x0%3F, 0xc0007f8800%3F})
	  stmt.go:125  0xc9
go/types.(*Checker).funcBody(0xc002f50000, 0xc002f33b00, {0x1bf2d70%3F, 0xc001762b88%3F}, 0xc002066b80, 0xc0021022a0, {0x0, 0x0})
	  stmt.go:46  0x285
go/types.(*Checker).funcDecl.func1()
	  decl.go:790  0x45
go/types.(*Checker).processDelayed(0xc002f50000, 0x0)
	  check.go:375  0x39
go/types.(*Checker).checkFiles(0xc002f50000, {0xc0016386e0%3F, 0xc002f08f00%3F, 0x0%3F})
	  check.go:326  0xcb
go/types.(*Checker).Files(...)
	  check.go:309
golang.org/x/tools/internal/lsp/cache.doTypeCheck({0x1bf64e0, 0xc001f05300}, 0xc00036b560, 0xc00081de00, 0x2, 0xc001014ae0, 0x19a8093%3F)
	  check.go:548  0x97b
golang.org/x/tools/internal/lsp/cache.typeCheck({0x1bf64e0, 0xc001f05300}, 0xc00036b560, 0xc00081de00, 0x2, 0xc001014ae0%3F)
	  check.go:314  0xe5
golang.org/x/tools/internal/lsp/cache.(*snapshot).buildPackageHandle.func1({0x1bf64e0%3F, 0xc001f05300}, {0x1befd00%3F, 0xc00036b560})
	  check.go:125  0x233
golang.org/x/tools/internal/memoize.(*Handle).run.func1()
	  memoize.go:327  0xa9
created by golang.org/x/tools/internal/memoize.(*Handle).run
	  memoize.go:320  0x1b8
[Error - 9:22:28 AM] 

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[findleyr]

CC @griesemer

[griesemer]

It appears that the Interface.check field is nil when we still need it for type set computation. There's the following places where we create an Interface w/o setting its check field during type checking:

• builtins.go calls NewInterface which doesn't set the check field (this happens only for real, imag and complex built-ins)
• named.go and subst.go allocate new interfaces through &Interface{...} without setting the check field

These seem wrong.

There may be places where we clear the check field but shouldn't, or where we throw away the type set (tset field set to nil) but don't have a Checker anymore but need one when the type set is recomputed.

[griesemer]

@wushilin Is there any possibility that you could send us a snippet of source code (not your analyzer or whatever tool is using go/types, but the code on which the tool is crashing)? That would be helpful for reproduction.

[gopherbot]

Change https://go.dev/cl/387417 mentions this issue: types2: generalize cleanup phase after type checking