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cmd/go2go: anonymous struct type as type parameter causes panic #39737

DeedleFake opened this issue Jun 21, 2020 · 3 comments

cmd/go2go: anonymous struct type as type parameter causes panic #39737

DeedleFake opened this issue Jun 21, 2020 · 3 comments


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@DeedleFake DeedleFake commented Jun 21, 2020


package main

import (

func Decode(type T)(r io.Reader) (T, error) {
	var t T
	err := json.NewDecoder(r).Decode(&t)
	return t, err

func main() {
	t, err := Decode(struct {
		This string `json:"this"`
		A    string `json:"a"`
	})(strings.NewReader(`{"this": "is", "a": "test"}`))
	if err != nil {
	fmt.Printf("%#v", t)


panic: prog.go2:17:12: unexpected type string character '"' in "struct{This string \"json:\\\"this\\\"\"; A string \"json:\\\"a\\\"\"}"

goroutine 1 [running]:
go/go2go.(*translator).instantiatedName(0xc0003f19b0, 0x0, 0xc00009a6a0, 0xc00001c4b0, 0x1, 0x1, 0xc0003f1158, 0x403518, 0x652e80, 0xc0003f1158)
	/usr/local/go-faketime/src/go/go2go/names.go:61 +0x72b
go/go2go.(*translator).instantiateFunction(0xc0003f19b0, 0x0, 0xc00009a6a0, 0xc0000826a0, 0x1, 0x1, 0xc00001c4b0, 0x1, 0x1, 0xc0003f1200, ...)
	/usr/local/go-faketime/src/go/go2go/instantiate.go:94 +0x85
go/go2go.(*translator).translateFunctionInstantiation(0xc0003f19b0, 0xc0000ae680)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:734 +0x3ea
go/go2go.(*translator).translateExpr(0xc0003f19b0, 0xc0000ae680)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:614 +0x3e5
go/go2go.(*translator).translateExpr(0xc0003f19b0, 0xc0000826e0)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:619 +0x398
go/go2go.(*translator).translateExprList(0xc0003f19b0, 0xc0000826e0, 0x1, 0x1)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:693 +0x46
go/go2go.(*translator).translateStmt(0xc0003f19b0, 0xc0000ae7c0)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:494 +0x29d
go/go2go.(*translator).translateBlockStmt(0xc0003f19b0, 0xc000084e40)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:455 +0x52
go/go2go.(*translator).translateFuncDecl(0xc0003f19b0, 0xc0000ae820)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:448 +0xc5
go/go2go.(*translator).translate(0xc0003f19b0, 0xc0000c2200)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:376 +0x391
go/go2go.rewriteAST(0xc0000ae240, 0xc0000b1360, 0x0, 0x0, 0xc0000b1720, 0xc0000c2200, 0x1, 0xc0000b1310, 0xc0000b1720)
	/usr/local/go-faketime/src/go/go2go/rewrite.go:188 +0x109
go/go2go.RewriteBuffer(0xc0000b1360, 0x7fff700f3dd8, 0x1e, 0xc0000f8000, 0x17f, 0x37f, 0x0, 0xc000084a20, 0xc0000849f0, 0xc0000849c0, ...)
	/usr/local/go-faketime/src/go/go2go/go2go.go:132 +0x2c5
main.translateFile(0xc0000b1360, 0x7fff700f3dd8, 0x1e)
	/usr/local/go-faketime/src/cmd/go2go/translate.go:26 +0xa9
	/usr/local/go-faketime/src/cmd/go2go/main.go:64 +0x2ea
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@DeedleFake DeedleFake commented Jun 21, 2020

This seems to be related to #39643, but it's still happening for this case.

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@gopherbot gopherbot commented Jun 22, 2020

Change mentions this issue: [dev.go2go] go/go2go: ignore struct tags

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@ianlancetaylor ianlancetaylor commented Jun 22, 2020

Thanks. This is now fixed in the dev.go2go branch.

gopherbot pushed a commit that referenced this issue Jun 22, 2020
Ignore struct tags when generating an instantiated names, and when
comparing types for identity.

Fixes #39737

Change-Id: I53e67fa1d09214dafc4088a59eb00e1a6f18ef3d
Reviewed-by: Ian Lance Taylor <>
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