2 files changed, 30 insertions, 4 deletions
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index 1d6321212e..41a9d8e9dc 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -398,10 +398,14 @@ func convFuncName(from, to *types.Type) (fnname string, needsaddr bool) {
 			return "convT32", false
 		case from.Size() == 8 && from.Align == types.Types[TUINT64].Align && !types.Haspointers(from):
 			return "convT64", false
-		case from.IsString():
-			return "convTstring", false
-		case from.IsSlice():
-			return "convTslice", false
+		}
+		if sc := from.SoleComponent(); sc != nil {
+			switch {
+			case sc.IsString():
+				return "convTstring", false
+			case sc.IsSlice():
+				return "convTslice", false
+			}
 		}
 
 		switch tkind {
diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index 7d123e4610..e2f3e66d8b 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -1395,6 +1395,28 @@ func (t *Type) NumComponents(countBlank componentsIncludeBlankFields) int64 {
 	return 1
 }
 
+// SoleComponent returns the only primitive component in t,
+// if there is exactly one. Otherwise, it returns nil.
+// Components are counted as in NumComponents, including blank fields.
+func (t *Type) SoleComponent() *Type {
+	switch t.Etype {
+	case TSTRUCT:
+		if t.IsFuncArgStruct() {
+			Fatalf("SoleComponent func arg struct")
+		}
+		if t.NumFields() != 1 {
+			return nil
+		}
+		return t.Field(0).Type.SoleComponent()
+	case TARRAY:
+		if t.NumElem() != 1 {
+			return nil
+		}
+		return t.Elem().SoleComponent()
+	}
+	return t
+}
+
 // ChanDir returns the direction of a channel type t.
 // The direction will be one of Crecv, Csend, or Cboth.
 func (t *Type) ChanDir() ChanDir {