1 files changed, 104 insertions, 0 deletions
diff --git a/go/ssa/const_test.go b/go/ssa/const_test.go
new file mode 100644
index 000000000..131fe1ace
--- /dev/null
+++ b/go/ssa/const_test.go
@@ -0,0 +1,104 @@
+// Copyright 2022 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 ssa_test
+
+import (
+	"go/ast"
+	"go/constant"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"math/big"
+	"strings"
+	"testing"
+
+	"golang.org/x/tools/go/ssa"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+func TestConstString(t *testing.T) {
+	if !typeparams.Enabled {
+		t.Skip("TestConstString requires type parameters.")
+	}
+
+	const source = `
+	package P
+
+	type Named string
+
+	func fn() (int, bool, string) 
+	func gen[T int]() {}
+	`
+	fset := token.NewFileSet()
+	f, err := parser.ParseFile(fset, "p.go", source, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var conf types.Config
+	pkg, err := conf.Check("P", fset, []*ast.File{f}, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	for _, test := range []struct {
+		expr     string      // type expression
+		constant interface{} // constant value
+		want     string      // expected String() value
+	}{
+		{"int", int64(0), "0:int"},
+		{"int64", int64(0), "0:int64"},
+		{"float32", int64(0), "0:float32"},
+		{"float32", big.NewFloat(1.5), "1.5:float32"},
+		{"bool", false, "false:bool"},
+		{"string", "", `"":string`},
+		{"Named", "", `"":P.Named`},
+		{"struct{x string}", nil, "struct{x string}{}:struct{x string}"},
+		{"[]int", nil, "nil:[]int"},
+		{"[3]int", nil, "[3]int{}:[3]int"},
+		{"*int", nil, "nil:*int"},
+		{"interface{}", nil, "nil:interface{}"},
+		{"interface{string}", nil, `"":interface{string}`},
+		{"interface{int|int64}", nil, "0:interface{int|int64}"},
+		{"interface{bool}", nil, "false:interface{bool}"},
+		{"interface{bool|int}", nil, "nil:interface{bool|int}"},
+		{"interface{int|string}", nil, "nil:interface{int|string}"},
+		{"interface{bool|string}", nil, "nil:interface{bool|string}"},
+		{"interface{struct{x string}}", nil, "nil:interface{struct{x string}}"},
+		{"interface{int|int64}", int64(1), "1:interface{int|int64}"},
+		{"interface{~bool}", true, "true:interface{~bool}"},
+		{"interface{Named}", "lorem ipsum", `"lorem ipsum":interface{P.Named}`},
+		{"func() (int, bool, string)", nil, "nil:func() (int, bool, string)"},
+	} {
+		// Eval() expr for its type.
+		tv, err := types.Eval(fset, pkg, 0, test.expr)
+		if err != nil {
+			t.Fatalf("Eval(%s) failed: %v", test.expr, err)
+		}
+		var val constant.Value
+		if test.constant != nil {
+			val = constant.Make(test.constant)
+		}
+		c := ssa.NewConst(val, tv.Type)
+		got := strings.ReplaceAll(c.String(), " | ", "|") // Accept both interface{a | b} and interface{a|b}.
+		if got != test.want {
+			t.Errorf("ssa.NewConst(%v, %s).String() = %v, want %v", val, tv.Type, got, test.want)
+		}
+	}
+
+	// Test tuples
+	fn := pkg.Scope().Lookup("fn")
+	tup := fn.Type().(*types.Signature).Results()
+	if got, want := ssa.NewConst(nil, tup).String(), `(0, false, ""):(int, bool, string)`; got != want {
+		t.Errorf("ssa.NewConst(%v, %s).String() = %v, want %v", nil, tup, got, want)
+	}
+
+	// Test type-param
+	gen := pkg.Scope().Lookup("gen")
+	tp := typeparams.ForSignature(gen.Type().(*types.Signature)).At(0)
+	if got, want := ssa.NewConst(nil, tp).String(), "0:T"; got != want {
+		t.Errorf("ssa.NewConst(%v, %s).String() = %v, want %v", nil, tup, got, want)
+	}
+}