go/types: panic("t.fromRHS = %s, typ = %s") in setDefType

[adonovan]

#!stacks
"runtime.gopanic" && "setDefType:+7"

Issue created by stacks.

func setDefType(def *TypeName, typ Type) {
	if def != nil {
		switch t := def.typ.(type) {
		case *Alias:
			// t.fromRHS should always be set, either to an invalid type
			// in the beginning, or to typ in certain cyclic declarations.
			if t.fromRHS != Typ[Invalid] && t.fromRHS != typ {
				panic(sprintf(nil, nil, true, "t.fromRHS = %s, typ = %s\n", t.fromRHS, typ))
			}
			t.fromRHS = typ
		case *Basic:
			assert(t == Typ[Invalid])
		case *Named:
			t.underlying = typ
		default:
			panic(fmt.Sprintf("unexpected type %T", t))
		}
	}
}

This stack PrtfKQ was reported by telemetry:

• crash/crash
• runtime.gopanic:+69
• go/types.(*Checker).handleBailout:+7
• go/types.(*Checker).Files.deferwrap1:+0
• runtime.gopanic:+50
• go/types.setDefType:+7
• go/types.(*Checker).typInternal:+175
• go/types.(*Checker).definedType:+1
• go/types.(*Checker).typeDecl:+55
• go/types.(*Checker).objDecl:+141
• go/types.(*Checker).packageObjects:+59
• go/types.(*Checker).checkFiles:+29
• go/types.(*Checker).Files:+13
• golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).checkPackage:+73
• golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).getPackage.func1:+49
• golang.org/x/tools/gopls/internal/cache.(*futureCache[...]).get:+32
• golang.org/x/tools/gopls/internal/cache.(*typeCheckBatch).getPackage:+1

golang.org/x/tools/gopls@v0.17.1 go1.23.4 linux/amd64 vscode (1)

cc @timothy-king

[gabyhelp]

Related Issues

• cmd/compile: bug in cmd/compile/internal/types2.setDefType #71010
• go.tools/go.types: goto _ crashes type checker #7537 (closed)
• x/tools/gopls: Completion: "ZeroString for unexpected type" panic #70744 (closed)
• go/types, types2: gopls crash on method with type parameters #50427 (closed)
• go.tools/go/types assertion failure in recordTypeAndValue #8169 (closed)
• go/types, types2: gopls crash in recordTypeAndValue #51658 (closed)
• go/types: panic when enabling reverseTypeInference with -lang=go1.17 #59639 (closed)
• go/types: assertion failed #11347 (closed)
• x/tools/go/types: panics on invalid constant #11325 (closed)
• go/types: panic in (*StdSizes).Sizeof when building github.com/kisielk/errcheck with Go tip #64347 (closed)

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[prattmic]

#71010 in the compiler might be the same bug?

[adonovan]

Yep!

Hey, you're using stacks for the compiler now? Nice!

[prattmic]

I've got a hacked up version in https://go.dev/cl/638775, but it needs clean up to support both gopls and the compiler.