go/types: recursive type aliases might cause a panic

[mateusz834]

Reproducer:

const src = `package A

type (
        A0 = A
        A  = A
)

`

func run() error {
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "test.go", src, parser.SkipObjectResolution)
	if err != nil {
		return err
	}
	_, err = (&types.Config{
		Error: func(err error) {},
	}).Check("test", fset, []*ast.File{f}, &types.Info{})
	return err
}

$ go run .
panic: t.fromRHS = test.A, typ = invalid type
         [recovered]
        panic: t.fromRHS = test.A, typ = invalid type


goroutine 1 [running]:
go/types.(*Checker).handleBailout(0xc000007500, 0xc00012be20)
        /usr/lib/go/src/go/types/check.go:404 +0x88
panic({0x584240?, 0xc000014210?})
        /usr/lib/go/src/runtime/panic.go:785 +0x132
go/types.setDefType(0xc000007500?, {0x5fbce0, 0x6f4720})
        /usr/lib/go/src/go/types/typexpr.go:422 +0x294
go/types.(*Checker).typInternal(0xc000007500, {0x5fbff8, 0xc0000780a0}, 0xc00010f3b0)
        /usr/lib/go/src/go/types/typexpr.go:267 +0x659
go/types.(*Checker).definedType(0xc000007500, {0x5fbff8, 0xc0000780a0}, 0x6f4720?)
        /usr/lib/go/src/go/types/typexpr.go:201 +0x2f
go/types.(*Checker).typeDecl(0xc000007500, 0xc00010f3b0, 0xc000100280, 0x0)
        /usr/lib/go/src/go/types/decl.go:610 +0x8cd
go/types.(*Checker).objDecl(0xc000007500, {0x5fe198, 0xc00010f3b0}, 0x0)
        /usr/lib/go/src/go/types/decl.go:191 +0xa3f
go/types.(*Checker).packageObjects(0xc000007500)
        /usr/lib/go/src/go/types/resolver.go:710 +0x408
go/types.(*Checker).checkFiles(0xc000007500, {0xc000106ef0, 0x1, 0x1})
        /usr/lib/go/src/go/types/check.go:459 +0x15a
go/types.(*Checker).Files(0x5b6095?, {0xc000106ef0?, 0xc0000326c0?, 0x0?})
        /usr/lib/go/src/go/types/check.go:422 +0x75
go/types.(*Config).Check(0xc00011c0e0, {0x5b6095?, 0x7?}, 0xc000100240, {0xc000106ef0, 0x1, 0x1}, 0xc000032600)
        /usr/lib/go/src/go/types/api.go:476 +0x79
main.run()
        /tmp/aa/main.go:32 +0xc5
main.main()
        /tmp/aa/main.go:12 +0x13
exit status 2

CC @adonovan @findleyr @griesemer

[mateusz834]

This was found by a fuzzer.

[findleyr]

Thank you. I believe this should also block the 1.24 release.

[gabyhelp]

Related Issues

• go/types: panic("t.fromRHS = %s, typ = %s") in setDefType #71029
• x/tools/go/types: panics on invalid constant #11325 (closed)
• go/types, types2: crash in typesSummary (which assumes well-typedness) #70526 (closed)
• go/types: assertion failed #11347 (closed)
• go.tools/go.types: goto _ crashes type checker #7537 (closed)
• cmd/go2go: A type alias that references a parameterized type in another package causes a panic #39792 (closed)
• cmd/go2go: "receiver type inference failed" panic on invalid type #40056 (closed)
• cmd/go2go: Panic in type checker #42522 (closed)
• go/types, types2: panic in eager error reporting for interface types #48234 (closed)
• go/types: panic when enabling reverseTypeInference with -lang=go1.17 #59639 (closed)

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[gopherbot]

Change https://go.dev/cl/643255 mentions this issue: go/types, types2: remove superfluous assertion (fix build)