1 files changed, 66 insertions, 1 deletions
diff --git a/src/cmd/compile/internal/types2/typeset_test.go b/src/cmd/compile/internal/types2/typeset_test.go
index 0e14d523c8..7f7cc06db9 100644
--- a/src/cmd/compile/internal/types2/typeset_test.go
+++ b/src/cmd/compile/internal/types2/typeset_test.go
@@ -4,7 +4,11 @@
 
 package types2
 
-import "testing"
+import (
+	"cmd/compile/internal/syntax"
+	"strings"
+	"testing"
+)
 
 func TestInvalidTypeSet(t *testing.T) {
 	if !invalidTypeSet.IsEmpty() {
@@ -12,4 +16,65 @@ func TestInvalidTypeSet(t *testing.T) {
 	}
 }
 
+func TestTypeSetString(t *testing.T) {
+	for body, want := range map[string]string{
+		"{}":            "𝓤",
+		"{int}":         "{int}",
+		"{~int}":        "{~int}",
+		"{int|string}":  "{int ∪ string}",
+		"{int; string}": "∅",
+
+		"{comparable}":              "{comparable}",
+		"{comparable; int}":         "{comparable; int}",
+		"{~int; comparable}":        "{comparable; ~int}",
+		"{int|string; comparable}":  "{comparable; int ∪ string}",
+		"{comparable; int; string}": "∅",
+
+		"{m()}":                         "{func (p.T).m()}",
+		"{m1(); m2() int }":             "{func (p.T).m1(); func (p.T).m2() int}",
+		"{error}":                       "{func (error).Error() string}",
+		"{m(); comparable}":             "{comparable; func (p.T).m()}",
+		"{m1(); comparable; m2() int }": "{comparable; func (p.T).m1(); func (p.T).m2() int}",
+		"{comparable; error}":           "{comparable; func (error).Error() string}",
+
+		"{m(); comparable; int|float32|string}": "{comparable; func (p.T).m(); int ∪ float32 ∪ string}",
+		"{m1(); int; m2(); comparable }":        "{comparable; func (p.T).m1(); func (p.T).m2(); int}",
+
+		"{E}; type E interface{}":           "𝓤",
+		"{E}; type E interface{int;string}": "∅",
+		"{E}; type E interface{comparable}": "{comparable}",
+	} {
+		// parse
+		errh := func(error) {} // dummy error handler so that parsing continues in presence of errors
+		src := "package p; type T interface" + body
+		file, err := syntax.Parse(nil, strings.NewReader(src), errh, nil, syntax.AllowGenerics)
+		if err != nil {
+			t.Fatalf("%s: %v (invalid test case)", body, err)
+		}
+
+		// type check
+		var conf Config
+		pkg, err := conf.Check(file.PkgName.Value, []*syntax.File{file}, nil)
+		if err != nil {
+			t.Fatalf("%s: %v (invalid test case)", body, err)
+		}
+
+		// lookup T
+		obj := pkg.scope.Lookup("T")
+		if obj == nil {
+			t.Fatalf("%s: T not found (invalid test case)", body)
+		}
+		T, ok := under(obj.Type()).(*Interface)
+		if !ok {
+			t.Fatalf("%s: %v is not an interface (invalid test case)", body, obj)
+		}
+
+		// verify test case
+		got := T.typeSet().String()
+		if got != want {
+			t.Errorf("%s: got %s; want %s", body, got, want)
+		}
+	}
+}
+
 // TODO(gri) add more tests