cmd/compile: save the note of fields when translating struct

Fixes #48317

Change-Id: I756ae6253022870071004332dd8f49169307f7e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/349013
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Trust: Dan Scales <danscales@google.com>

diff --git a/src/cmd/compile/internal/typecheck/subr.go b/src/cmd/compile/internal/typecheck/subr.go
index 34f20879f10a043b90abcc855df687144b6dd393..5323872eafdf8b10711b70702ed3e6084b6f6e6b 100644 (file)
--- a/src/cmd/compile/internal/typecheck/subr.go
+++ b/src/cmd/compile/internal/typecheck/subr.go
@@ -1312,6 +1312,7 @@ func (ts *Tsubster) tstruct(t *types.Type, force bool) *types.Type {
                        // the type param, not the instantiated type).
                        newfields[i] = types.NewField(f.Pos, f.Sym, t2)
                        newfields[i].Embedded = f.Embedded
+                       newfields[i].Note = f.Note
                        if f.IsDDD() {
                                newfields[i].SetIsDDD(true)
                        }

diff --git a/test/typeparam/issue48317.go b/test/typeparam/issue48317.go
new file mode 100644 (file)
index 0000000..c8f088d
--- /dev/null
+++ b/test/typeparam/issue48317.go
@@ -0,0 +1,38 @@
+// run -gcflags="-G=3"
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+       "encoding/json"
+)
+
+type A[T any] struct {
+       F1 string `json:"t1"`
+       F2 T      `json:"t2"`
+       B  B      `json:"t3"`
+}
+
+type B struct {
+       F4 int `json:"t4"`
+}
+
+func a[T any]() {
+       data := `{"t1":"1","t2":2,"t3":{"t4":4}}`
+       a1 := A[T]{}
+       if err := json.Unmarshal([]byte(data), &a1); err != nil {
+               panic(err)
+       }
+       if bytes, err := json.Marshal(&a1); err != nil {
+               panic(err)
+       } else if string(bytes) != data {
+               panic(string(bytes))
+       }
+}
+
+func main() {
+       a[int]()
+}