cmd/compile: fix CONVIFACE case converting interface to empty interface

We need an extra case in convertToDictionary. In the case of an operand
which is an interface and converting to an empty interface, we don't
want to get the run-time type from the dictionary (which would be the
run-time type of the interface). We want to do a type-assert to the
empty interface.

Change-Id: I414247210168153151272fab198bfe82ad7b1567
Reviewed-on: https://go-review.googlesource.com/c/go/+/342009
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Trust: Dan Scales <danscales@google.com>

diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index 6736f128e31d8f77aae31792d0e65907c17a0d18..4ac37c362cc20a8f05c660d49aac2d0728ab6b3e 100644 (file)
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -1224,6 +1224,11 @@ func convertUsingDictionary(info *instInfo, dictParam *ir.Name, pos src.XPos, v
                }
                assert(ix >= 0)
                rt = getDictionaryEntry(pos, dictParam, ix, info.dictLen)
+       } else if v.Type().IsInterface() {
+               ta := ir.NewTypeAssertExpr(pos, v, nil)
+               ta.SetType(dst)
+               ta.SetTypecheck(1)
+               return ta
        } else {
                ix := findDictType(info, src)
                assert(ix >= 0)

diff --git a/test/typeparam/issue47272.go b/test/typeparam/issue47272.go
new file mode 100644 (file)
index 0000000..6771cb9
--- /dev/null
+++ b/test/typeparam/issue47272.go
@@ -0,0 +1,55 @@
+// 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 (
+       "errors"
+       "fmt"
+)
+
+type Option[T any] struct {
+       ok  bool
+       val T
+}
+
+func (o Option[T]) String() string {
+       if o.ok {
+               return fmt.Sprintf("Some(%v)", o.val)
+       }
+       return "None"
+}
+
+func Some[T any](val T) Option[T] { return Option[T]{ok: true, val: val} }
+func None[T any]() Option[T]      { return Option[T]{ok: false} }
+
+type Result[T, E any] struct {
+       ok  bool
+       val T
+       err E
+}
+
+func (r Result[T, E]) String() string {
+       if r.ok {
+               return fmt.Sprintf("Ok(%v)", r.val)
+       }
+       return fmt.Sprintf("Err(%v)", r.err)
+}
+
+func Ok[T, E any](val T) Result[T, E]  { return Result[T, E]{ok: true, val: val} }
+func Err[T, E any](err E) Result[T, E] { return Result[T, E]{ok: false, err: err} }
+
+func main() {
+       a := Some[int](1)
+       b := None[int]()
+       fmt.Println(a, b)
+
+       x := Ok[int, error](1)
+       y := Err[int, error](errors.New("test"))
+       fmt.Println(x, y)
+       // fmt.Println(x)
+       _, _, _, _ = a, b, x, y
+}

diff --git a/test/typeparam/issue47272.out b/test/typeparam/issue47272.out
new file mode 100644 (file)
index 0000000..9c433fa
--- /dev/null
+++ b/test/typeparam/issue47272.out
@@ -0,0 +1,2 @@
+Some(1) None
+Ok(1) Err(test)