// Copyright 2013 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 types_test

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"strings"
	"testing"

	_ "llvm.org/llgo/third_party/go.tools/go/gcimporter"
	. "llvm.org/llgo/third_party/go.tools/go/types"
)

func pkgFor(path, source string, info *Info) (*Package, error) {
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, path, source, 0)
	if err != nil {
		return nil, err
	}

	var conf Config
	return conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
}

func mustTypecheck(t *testing.T, path, source string, info *Info) string {
	pkg, err := pkgFor(path, source, info)
	if err != nil {
		name := path
		if pkg != nil {
			name = "package " + pkg.Name()
		}
		t.Fatalf("%s: didn't type-check (%s)", name, err)
	}
	return pkg.Name()
}

func TestValuesInfo(t *testing.T) {
	var tests = []struct {
		src  string
		expr string // constant expression
		typ  string // constant type
		val  string // constant value
	}{
		{`package a0; const _ = false`, `false`, `untyped bool`, `false`},
		{`package a1; const _ = 0`, `0`, `untyped int`, `0`},
		{`package a2; const _ = 'A'`, `'A'`, `untyped rune`, `65`},
		{`package a3; const _ = 0.`, `0.`, `untyped float`, `0`},
		{`package a4; const _ = 0i`, `0i`, `untyped complex`, `0`},
		{`package a5; const _ = "foo"`, `"foo"`, `untyped string`, `"foo"`},

		{`package b0; var _ = false`, `false`, `bool`, `false`},
		{`package b1; var _ = 0`, `0`, `int`, `0`},
		{`package b2; var _ = 'A'`, `'A'`, `rune`, `65`},
		{`package b3; var _ = 0.`, `0.`, `float64`, `0`},
		{`package b4; var _ = 0i`, `0i`, `complex128`, `0`},
		{`package b5; var _ = "foo"`, `"foo"`, `string`, `"foo"`},

		{`package c0a; var _ = bool(false)`, `false`, `bool`, `false`},
		{`package c0b; var _ = bool(false)`, `bool(false)`, `bool`, `false`},
		{`package c0c; type T bool; var _ = T(false)`, `T(false)`, `c0c.T`, `false`},

		{`package c1a; var _ = int(0)`, `0`, `int`, `0`},
		{`package c1b; var _ = int(0)`, `int(0)`, `int`, `0`},
		{`package c1c; type T int; var _ = T(0)`, `T(0)`, `c1c.T`, `0`},

		{`package c2a; var _ = rune('A')`, `'A'`, `rune`, `65`},
		{`package c2b; var _ = rune('A')`, `rune('A')`, `rune`, `65`},
		{`package c2c; type T rune; var _ = T('A')`, `T('A')`, `c2c.T`, `65`},

		{`package c3a; var _ = float32(0.)`, `0.`, `float32`, `0`},
		{`package c3b; var _ = float32(0.)`, `float32(0.)`, `float32`, `0`},
		{`package c3c; type T float32; var _ = T(0.)`, `T(0.)`, `c3c.T`, `0`},

		{`package c4a; var _ = complex64(0i)`, `0i`, `complex64`, `0`},
		{`package c4b; var _ = complex64(0i)`, `complex64(0i)`, `complex64`, `0`},
		{`package c4c; type T complex64; var _ = T(0i)`, `T(0i)`, `c4c.T`, `0`},

		{`package c5a; var _ = string("foo")`, `"foo"`, `string`, `"foo"`},
		{`package c5b; var _ = string("foo")`, `string("foo")`, `string`, `"foo"`},
		{`package c5c; type T string; var _ = T("foo")`, `T("foo")`, `c5c.T`, `"foo"`},

		{`package d0; var _ = []byte("foo")`, `"foo"`, `string`, `"foo"`},
		{`package d1; var _ = []byte(string("foo"))`, `"foo"`, `string`, `"foo"`},
		{`package d2; var _ = []byte(string("foo"))`, `string("foo")`, `string`, `"foo"`},
		{`package d3; type T []byte; var _ = T("foo")`, `"foo"`, `string`, `"foo"`},

		{`package e0; const _ = float32( 1e-200)`, `float32(1e-200)`, `float32`, `0`},
		{`package e1; const _ = float32(-1e-200)`, `float32(-1e-200)`, `float32`, `0`},
		{`package e2; const _ = float64( 1e-2000)`, `float64(1e-2000)`, `float64`, `0`},
		{`package e3; const _ = float64(-1e-2000)`, `float64(-1e-2000)`, `float64`, `0`},
		{`package e4; const _ = complex64( 1e-200)`, `complex64(1e-200)`, `complex64`, `0`},
		{`package e5; const _ = complex64(-1e-200)`, `complex64(-1e-200)`, `complex64`, `0`},
		{`package e6; const _ = complex128( 1e-2000)`, `complex128(1e-2000)`, `complex128`, `0`},
		{`package e7; const _ = complex128(-1e-2000)`, `complex128(-1e-2000)`, `complex128`, `0`},

		{`package f0 ; var _ float32 =  1e-200`, `1e-200`, `float32`, `0`},
		{`package f1 ; var _ float32 = -1e-200`, `-1e-200`, `float32`, `0`},
		{`package f2a; var _ float64 =  1e-2000`, `1e-2000`, `float64`, `0`},
		{`package f3a; var _ float64 = -1e-2000`, `-1e-2000`, `float64`, `0`},
		{`package f2b; var _         =  1e-2000`, `1e-2000`, `float64`, `0`},
		{`package f3b; var _         = -1e-2000`, `-1e-2000`, `float64`, `0`},
		{`package f4 ; var _ complex64  =  1e-200 `, `1e-200`, `complex64`, `0`},
		{`package f5 ; var _ complex64  = -1e-200 `, `-1e-200`, `complex64`, `0`},
		{`package f6a; var _ complex128 =  1e-2000i`, `1e-2000i`, `complex128`, `0`},
		{`package f7a; var _ complex128 = -1e-2000i`, `-1e-2000i`, `complex128`, `0`},
		{`package f6b; var _            =  1e-2000i`, `1e-2000i`, `complex128`, `0`},
		{`package f7b; var _            = -1e-2000i`, `-1e-2000i`, `complex128`, `0`},
	}

	for _, test := range tests {
		info := Info{
			Types: make(map[ast.Expr]TypeAndValue),
		}
		name := mustTypecheck(t, "ValuesInfo", test.src, &info)

		// look for constant expression
		var expr ast.Expr
		for e := range info.Types {
			if ExprString(e) == test.expr {
				expr = e
				break
			}
		}
		if expr == nil {
			t.Errorf("package %s: no expression found for %s", name, test.expr)
			continue
		}
		tv := info.Types[expr]

		// check that type is correct
		if got := tv.Type.String(); got != test.typ {
			t.Errorf("package %s: got type %s; want %s", name, got, test.typ)
			continue
		}

		// check that value is correct
		if got := tv.Value.String(); got != test.val {
			t.Errorf("package %s: got value %s; want %s", name, got, test.val)
		}
	}
}

func TestTypesInfo(t *testing.T) {
	var tests = []struct {
		src  string
		expr string // expression
		typ  string // value type
	}{
		// single-valued expressions of untyped constants
		{`package b0; var x interface{} = false`, `false`, `bool`},
		{`package b1; var x interface{} = 0`, `0`, `int`},
		{`package b2; var x interface{} = 0.`, `0.`, `float64`},
		{`package b3; var x interface{} = 0i`, `0i`, `complex128`},
		{`package b4; var x interface{} = "foo"`, `"foo"`, `string`},

		// comma-ok expressions
		{`package p0; var x interface{}; var _, _ = x.(int)`,
			`x.(int)`,
			`(int, bool)`,
		},
		{`package p1; var x interface{}; func _() { _, _ = x.(int) }`,
			`x.(int)`,
			`(int, bool)`,
		},
		// TODO(gri): uncomment if we accept issue 8189.
		// {`package p2; type mybool bool; var m map[string]complex128; var b mybool; func _() { _, b = m["foo"] }`,
		// 	`m["foo"]`,
		// 	`(complex128, p2.mybool)`,
		// },
		// TODO(gri): remove if we accept issue 8189.
		{`package p2; var m map[string]complex128; var b bool; func _() { _, b = m["foo"] }`,
			`m["foo"]`,
			`(complex128, bool)`,
		},
		{`package p3; var c chan string; var _, _ = <-c`,
			`<-c`,
			`(string, bool)`,
		},

		// issue 6796
		{`package issue6796_a; var x interface{}; var _, _ = (x.(int))`,
			`x.(int)`,
			`(int, bool)`,
		},
		{`package issue6796_b; var c chan string; var _, _ = (<-c)`,
			`(<-c)`,
			`(string, bool)`,
		},
		{`package issue6796_c; var c chan string; var _, _ = (<-c)`,
			`<-c`,
			`(string, bool)`,
		},
		{`package issue6796_d; var c chan string; var _, _ = ((<-c))`,
			`(<-c)`,
			`(string, bool)`,
		},
		{`package issue6796_e; func f(c chan string) { _, _ = ((<-c)) }`,
			`(<-c)`,
			`(string, bool)`,
		},

		// issue 7060
		{`package issue7060_a; var ( m map[int]string; x, ok = m[0] )`,
			`m[0]`,
			`(string, bool)`,
		},
		{`package issue7060_b; var ( m map[int]string; x, ok interface{} = m[0] )`,
			`m[0]`,
			`(string, bool)`,
		},
		{`package issue7060_c; func f(x interface{}, ok bool, m map[int]string) { x, ok = m[0] }`,
			`m[0]`,
			`(string, bool)`,
		},
		{`package issue7060_d; var ( ch chan string; x, ok = <-ch )`,
			`<-ch`,
			`(string, bool)`,
		},
		{`package issue7060_e; var ( ch chan string; x, ok interface{} = <-ch )`,
			`<-ch`,
			`(string, bool)`,
		},
		{`package issue7060_f; func f(x interface{}, ok bool, ch chan string) { x, ok = <-ch }`,
			`<-ch`,
			`(string, bool)`,
		},
	}

	for _, test := range tests {
		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
		name := mustTypecheck(t, "TypesInfo", test.src, &info)

		// look for expression type
		var typ Type
		for e, tv := range info.Types {
			if ExprString(e) == test.expr {
				typ = tv.Type
				break
			}
		}
		if typ == nil {
			t.Errorf("package %s: no type found for %s", name, test.expr)
			continue
		}

		// check that type is correct
		if got := typ.String(); got != test.typ {
			t.Errorf("package %s: got %s; want %s", name, got, test.typ)
		}
	}
}

func predString(tv TypeAndValue) string {
	var buf bytes.Buffer
	pred := func(b bool, s string) {
		if b {
			if buf.Len() > 0 {
				buf.WriteString(", ")
			}
			buf.WriteString(s)
		}
	}

	pred(tv.IsVoid(), "void")
	pred(tv.IsType(), "type")
	pred(tv.IsBuiltin(), "builtin")
	pred(tv.IsValue() && tv.Value != nil, "const")
	pred(tv.IsValue() && tv.Value == nil, "value")
	pred(tv.IsNil(), "nil")
	pred(tv.Addressable(), "addressable")
	pred(tv.Assignable(), "assignable")
	pred(tv.HasOk(), "hasOk")

	if buf.Len() == 0 {
		return "invalid"
	}
	return buf.String()
}

func TestPredicatesInfo(t *testing.T) {
	var tests = []struct {
		src  string
		expr string
		pred string
	}{
		// void
		{`package n0; func f() { f() }`, `f()`, `void`},

		// types
		{`package t0; type _ int`, `int`, `type`},
		{`package t1; type _ []int`, `[]int`, `type`},
		{`package t2; type _ func()`, `func()`, `type`},

		// built-ins
		{`package b0; var _ = len("")`, `len`, `builtin`},
		{`package b1; var _ = (len)("")`, `(len)`, `builtin`},

		// constants
		{`package c0; var _ = 42`, `42`, `const`},
		{`package c1; var _ = "foo" + "bar"`, `"foo" + "bar"`, `const`},
		{`package c2; const (i = 1i; _ = i)`, `i`, `const`},

		// values
		{`package v0; var (a, b int; _ = a + b)`, `a + b`, `value`},
		{`package v1; var _ = &[]int{1}`, `([]int literal)`, `value`},
		{`package v2; var _ = func(){}`, `(func() literal)`, `value`},
		{`package v4; func f() { _ = f }`, `f`, `value`},
		{`package v3; var _ *int = nil`, `nil`, `value, nil`},
		{`package v3; var _ *int = (nil)`, `(nil)`, `value, nil`},

		// addressable (and thus assignable) operands
		{`package a0; var (x int; _ = x)`, `x`, `value, addressable, assignable`},
		{`package a1; var (p *int; _ = *p)`, `*p`, `value, addressable, assignable`},
		{`package a2; var (s []int; _ = s[0])`, `s[0]`, `value, addressable, assignable`},
		{`package a3; var (s struct{f int}; _ = s.f)`, `s.f`, `value, addressable, assignable`},
		{`package a4; var (a [10]int; _ = a[0])`, `a[0]`, `value, addressable, assignable`},
		{`package a5; func _(x int) { _ = x }`, `x`, `value, addressable, assignable`},
		{`package a6; func _()(x int) { _ = x; return }`, `x`, `value, addressable, assignable`},
		{`package a7; type T int; func (x T) _() { _ = x }`, `x`, `value, addressable, assignable`},
		// composite literals are not addressable

		// assignable but not addressable values
		{`package s0; var (m map[int]int; _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
		{`package s1; var (m map[int]int; _, _ = m[0])`, `m[0]`, `value, assignable, hasOk`},

		// hasOk expressions
		{`package k0; var (ch chan int; _ = <-ch)`, `<-ch`, `value, hasOk`},
		{`package k1; var (ch chan int; _, _ = <-ch)`, `<-ch`, `value, hasOk`},

		// missing entries
		// - package names are collected in the Uses map
		// - identifiers being declared are collected in the Defs map
		{`package m0; import "os"; func _() { _ = os.Stdout }`, `os`, `<missing>`},
		{`package m1; import p "os"; func _() { _ = p.Stdout }`, `p`, `<missing>`},
		{`package m2; const c = 0`, `c`, `<missing>`},
		{`package m3; type T int`, `T`, `<missing>`},
		{`package m4; var v int`, `v`, `<missing>`},
		{`package m5; func f() {}`, `f`, `<missing>`},
		{`package m6; func _(x int) {}`, `x`, `<missing>`},
		{`package m6; func _()(x int) { return }`, `x`, `<missing>`},
		{`package m6; type T int; func (x T) _() {}`, `x`, `<missing>`},
	}

	for _, test := range tests {
		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
		name := mustTypecheck(t, "PredicatesInfo", test.src, &info)

		// look for expression predicates
		got := "<missing>"
		for e, tv := range info.Types {
			//println(name, ExprString(e))
			if ExprString(e) == test.expr {
				got = predString(tv)
				break
			}
		}

		if got != test.pred {
			t.Errorf("package %s: got %s; want %s", name, got, test.pred)
		}
	}
}

func TestScopesInfo(t *testing.T) {
	var tests = []struct {
		src    string
		scopes []string // list of scope descriptors of the form kind:varlist
	}{
		{`package p0`, []string{
			"file:",
		}},
		{`package p1; import ( "fmt"; m "math"; _ "os" ); var ( _ = fmt.Println; _ = m.Pi )`, []string{
			"file:fmt m",
		}},
		{`package p2; func _() {}`, []string{
			"file:", "func:",
		}},
		{`package p3; func _(x, y int) {}`, []string{
			"file:", "func:x y",
		}},
		{`package p4; func _(x, y int) { x, z := 1, 2; _ = z }`, []string{
			"file:", "func:x y z", // redeclaration of x
		}},
		{`package p5; func _(x, y int) (u, _ int) { return }`, []string{
			"file:", "func:u x y",
		}},
		{`package p6; func _() { { var x int; _ = x } }`, []string{
			"file:", "func:", "block:x",
		}},
		{`package p7; func _() { if true {} }`, []string{
			"file:", "func:", "if:", "block:",
		}},
		{`package p8; func _() { if x := 0; x < 0 { y := x; _ = y } }`, []string{
			"file:", "func:", "if:x", "block:y",
		}},
		{`package p9; func _() { switch x := 0; x {} }`, []string{
			"file:", "func:", "switch:x",
		}},
		{`package p10; func _() { switch x := 0; x { case 1: y := x; _ = y; default: }}`, []string{
			"file:", "func:", "switch:x", "case:y", "case:",
		}},
		{`package p11; func _(t interface{}) { switch t.(type) {} }`, []string{
			"file:", "func:t", "type switch:",
		}},
		{`package p12; func _(t interface{}) { switch t := t; t.(type) {} }`, []string{
			"file:", "func:t", "type switch:t",
		}},
		{`package p13; func _(t interface{}) { switch x := t.(type) { case int: _ = x } }`, []string{
			"file:", "func:t", "type switch:", "case:x", // x implicitly declared
		}},
		{`package p14; func _() { select{} }`, []string{
			"file:", "func:",
		}},
		{`package p15; func _(c chan int) { select{ case <-c: } }`, []string{
			"file:", "func:c", "comm:",
		}},
		{`package p16; func _(c chan int) { select{ case i := <-c: x := i; _ = x} }`, []string{
			"file:", "func:c", "comm:i x",
		}},
		{`package p17; func _() { for{} }`, []string{
			"file:", "func:", "for:", "block:",
		}},
		{`package p18; func _(n int) { for i := 0; i < n; i++ { _ = i } }`, []string{
			"file:", "func:n", "for:i", "block:",
		}},
		{`package p19; func _(a []int) { for i := range a { _ = i} }`, []string{
			"file:", "func:a", "range:i", "block:",
		}},
		{`package p20; var s int; func _(a []int) { for i, x := range a { s += x; _ = i } }`, []string{
			"file:", "func:a", "range:i x", "block:",
		}},
	}

	for _, test := range tests {
		info := Info{Scopes: make(map[ast.Node]*Scope)}
		name := mustTypecheck(t, "ScopesInfo", test.src, &info)

		// number of scopes must match
		if len(info.Scopes) != len(test.scopes) {
			t.Errorf("package %s: got %d scopes; want %d", name, len(info.Scopes), len(test.scopes))
		}

		// scope descriptions must match
		for node, scope := range info.Scopes {
			kind := "<unknown node kind>"
			switch node.(type) {
			case *ast.File:
				kind = "file"
			case *ast.FuncType:
				kind = "func"
			case *ast.BlockStmt:
				kind = "block"
			case *ast.IfStmt:
				kind = "if"
			case *ast.SwitchStmt:
				kind = "switch"
			case *ast.TypeSwitchStmt:
				kind = "type switch"
			case *ast.CaseClause:
				kind = "case"
			case *ast.CommClause:
				kind = "comm"
			case *ast.ForStmt:
				kind = "for"
			case *ast.RangeStmt:
				kind = "range"
			}

			// look for matching scope description
			desc := kind + ":" + strings.Join(scope.Names(), " ")
			found := false
			for _, d := range test.scopes {
				if desc == d {
					found = true
					break
				}
			}
			if !found {
				t.Errorf("package %s: no matching scope found for %s", name, desc)
			}
		}
	}
}

func TestInitOrderInfo(t *testing.T) {
	var tests = []struct {
		src   string
		inits []string
	}{
		{`package p0; var (x = 1; y = x)`, []string{
			"x = 1", "y = x",
		}},
		{`package p1; var (a = 1; b = 2; c = 3)`, []string{
			"a = 1", "b = 2", "c = 3",
		}},
		{`package p2; var (a, b, c = 1, 2, 3)`, []string{
			"a = 1", "b = 2", "c = 3",
		}},
		{`package p3; var _ = f(); func f() int { return 1 }`, []string{
			"_ = f()", // blank var
		}},
		{`package p4; var (a = 0; x = y; y = z; z = 0)`, []string{
			"a = 0", "z = 0", "y = z", "x = y",
		}},
		{`package p5; var (a, _ = m[0]; m map[int]string)`, []string{
			"a, _ = m[0]", // blank var
		}},
		{`package p6; var a, b = f(); func f() (_, _ int) { return z, z }; var z = 0`, []string{
			"z = 0", "a, b = f()",
		}},
		{`package p7; var (a = func() int { return b }(); b = 1)`, []string{
			"b = 1", "a = (func() int literal)()",
		}},
		{`package p8; var (a, b = func() (_, _ int) { return c, c }(); c = 1)`, []string{
			"c = 1", "a, b = (func() (_, _ int) literal)()",
		}},
		{`package p9; type T struct{}; func (T) m() int { _ = y; return 0 }; var x, y = T.m, 1`, []string{
			"y = 1", "x = T.m",
		}},
		{`package p10; var (d = c + b; a = 0; b = 0; c = 0)`, []string{
			"a = 0", "b = 0", "c = 0", "d = c + b",
		}},
		{`package p11; var (a = e + c; b = d + c; c = 0; d = 0; e = 0)`, []string{
			"c = 0", "d = 0", "b = d + c", "e = 0", "a = e + c",
		}},
		// emit an initializer for n:1 initializations only once (not for each node
		// on the lhs which may appear in different order in the dependency graph)
		{`package p12; var (a = x; b = 0; x, y = m[0]; m map[int]int)`, []string{
			"b = 0", "x, y = m[0]", "a = x",
		}},
		// test case from spec section on package initialization
		{`package p12

		var (
			a = c + b
			b = f()
			c = f()
			d = 3
		)

		func f() int {
			d++
			return d
		}`, []string{
			"d = 3", "b = f()", "c = f()", "a = c + b",
		}},
		// test case for issue 7131
		{`package main

		var counter int
		func next() int { counter++; return counter }

		var _ = makeOrder()
		func makeOrder() []int { return []int{f, b, d, e, c, a} }

		var a       = next()
		var b, c    = next(), next()
		var d, e, f = next(), next(), next()
		`, []string{
			"a = next()", "b = next()", "c = next()", "d = next()", "e = next()", "f = next()", "_ = makeOrder()",
		}},
	}

	for _, test := range tests {
		info := Info{}
		name := mustTypecheck(t, "InitOrderInfo", test.src, &info)

		// number of initializers must match
		if len(info.InitOrder) != len(test.inits) {
			t.Errorf("package %s: got %d initializers; want %d", name, len(info.InitOrder), len(test.inits))
			continue
		}

		// initializers must match
		for i, want := range test.inits {
			got := info.InitOrder[i].String()
			if got != want {
				t.Errorf("package %s, init %d: got %s; want %s", name, i, got, want)
				continue
			}
		}
	}
}

func TestMultiFileInitOrder(t *testing.T) {
	fset := token.NewFileSet()
	mustParse := func(src string) *ast.File {
		f, err := parser.ParseFile(fset, "main", src, 0)
		if err != nil {
			t.Fatal(err)
		}
		return f
	}

	fileA := mustParse(`package main; var a = 1`)
	fileB := mustParse(`package main; var b = 2`)

	// The initialization order must not depend on the parse
	// order of the files, only on the presentation order to
	// the type-checker.
	for _, test := range []struct {
		files []*ast.File
		want  string
	}{
		{[]*ast.File{fileA, fileB}, "[a = 1 b = 2]"},
		{[]*ast.File{fileB, fileA}, "[b = 2 a = 1]"},
	} {
		var info Info
		if _, err := new(Config).Check("main", fset, test.files, &info); err != nil {
			t.Fatal(err)
		}
		if got := fmt.Sprint(info.InitOrder); got != test.want {
			t.Fatalf("got %s; want %s", got, test.want)
		}
	}
}

func TestFiles(t *testing.T) {
	var sources = []string{
		"package p; type T struct{}; func (T) m1() {}",
		"package p; func (T) m2() {}; var x interface{ m1(); m2() } = T{}",
		"package p; func (T) m3() {}; var y interface{ m1(); m2(); m3() } = T{}",
		"package p",
	}

	var conf Config
	fset := token.NewFileSet()
	pkg := NewPackage("p", "p")
	var info Info
	check := NewChecker(&conf, fset, pkg, &info)

	for i, src := range sources {
		filename := fmt.Sprintf("sources%d", i)
		f, err := parser.ParseFile(fset, filename, src, 0)
		if err != nil {
			t.Fatal(err)
		}
		if err := check.Files([]*ast.File{f}); err != nil {
			t.Error(err)
		}
	}

	// check InitOrder is [x y]
	var vars []string
	for _, init := range info.InitOrder {
		for _, v := range init.Lhs {
			vars = append(vars, v.Name())
		}
	}
	if got, want := fmt.Sprint(vars), "[x y]"; got != want {
		t.Errorf("InitOrder == %s, want %s", got, want)
	}
}

func TestSelection(t *testing.T) {
	selections := make(map[*ast.SelectorExpr]*Selection)

	fset := token.NewFileSet()
	conf := Config{
		Packages: make(map[string]*Package),
		Import: func(imports map[string]*Package, path string) (*Package, error) {
			return imports[path], nil
		},
	}
	makePkg := func(path, src string) {
		f, err := parser.ParseFile(fset, path+".go", src, 0)
		if err != nil {
			t.Fatal(err)
		}
		pkg, err := conf.Check(path, fset, []*ast.File{f}, &Info{Selections: selections})
		if err != nil {
			t.Fatal(err)
		}
		conf.Packages[path] = pkg
	}

	const libSrc = `
package lib
type T float64
const C T = 3
var V T
func F() {}
func (T) M() {}
`
	const mainSrc = `
package main
import "lib"

type A struct {
	*B
	C
}

type B struct {
	b int
}

func (B) f(int)

type C struct {
	c int
}

func (C) g()
func (*C) h()

func main() {
	// qualified identifiers
	var _ lib.T
        _ = lib.C
        _ = lib.F
        _ = lib.V
	_ = lib.T.M

	// fields
	_ = A{}.B
	_ = new(A).B

	_ = A{}.C
	_ = new(A).C

	_ = A{}.b
	_ = new(A).b

	_ = A{}.c
	_ = new(A).c

	// methods
        _ = A{}.f
        _ = new(A).f
        _ = A{}.g
        _ = new(A).g
        _ = new(A).h

        _ = B{}.f
        _ = new(B).f

        _ = C{}.g
        _ = new(C).g
        _ = new(C).h

	// method expressions
        _ = A.f
        _ = (*A).f
        _ = B.f
        _ = (*B).f
}`

	wantOut := map[string][2]string{
		"lib.T.M": {"method expr (lib.T) M(lib.T)", ".[0]"},

		"A{}.B":    {"field (main.A) B *main.B", ".[0]"},
		"new(A).B": {"field (*main.A) B *main.B", "->[0]"},
		"A{}.C":    {"field (main.A) C main.C", ".[1]"},
		"new(A).C": {"field (*main.A) C main.C", "->[1]"},
		"A{}.b":    {"field (main.A) b int", "->[0 0]"},
		"new(A).b": {"field (*main.A) b int", "->[0 0]"},
		"A{}.c":    {"field (main.A) c int", ".[1 0]"},
		"new(A).c": {"field (*main.A) c int", "->[1 0]"},

		"A{}.f":    {"method (main.A) f(int)", "->[0 0]"},
		"new(A).f": {"method (*main.A) f(int)", "->[0 0]"},
		"A{}.g":    {"method (main.A) g()", ".[1 0]"},
		"new(A).g": {"method (*main.A) g()", "->[1 0]"},
		"new(A).h": {"method (*main.A) h()", "->[1 1]"}, // TODO(gri) should this report .[1 1] ?
		"B{}.f":    {"method (main.B) f(int)", ".[0]"},
		"new(B).f": {"method (*main.B) f(int)", "->[0]"},
		"C{}.g":    {"method (main.C) g()", ".[0]"},
		"new(C).g": {"method (*main.C) g()", "->[0]"},
		"new(C).h": {"method (*main.C) h()", "->[1]"}, // TODO(gri) should this report .[1] ?

		"A.f":    {"method expr (main.A) f(main.A, int)", "->[0 0]"},
		"(*A).f": {"method expr (*main.A) f(*main.A, int)", "->[0 0]"},
		"B.f":    {"method expr (main.B) f(main.B, int)", ".[0]"},
		"(*B).f": {"method expr (*main.B) f(*main.B, int)", "->[0]"},
	}

	makePkg("lib", libSrc)
	makePkg("main", mainSrc)

	for e, sel := range selections {
		sel.String() // assertion: must not panic

		start := fset.Position(e.Pos()).Offset
		end := fset.Position(e.End()).Offset
		syntax := mainSrc[start:end] // (all SelectorExprs are in main, not lib)

		direct := "."
		if sel.Indirect() {
			direct = "->"
		}
		got := [2]string{
			sel.String(),
			fmt.Sprintf("%s%v", direct, sel.Index()),
		}
		want := wantOut[syntax]
		if want != got {
			t.Errorf("%s: got %q; want %q", syntax, got, want)
		}
		delete(wantOut, syntax)

		// We must explicitly assert properties of the
		// Signature's receiver since it doesn't participate
		// in Identical() or String().
		sig, _ := sel.Type().(*Signature)
		if sel.Kind() == MethodVal {
			got := sig.Recv().Type()
			want := sel.Recv()
			if !Identical(got, want) {
				t.Errorf("%s: Recv() = %s, want %s", got, want)
			}
		} else if sig != nil && sig.Recv() != nil {
			t.Error("%s: signature has receiver %s", sig, sig.Recv().Type())
		}
	}
	// Assert that all wantOut entries were used exactly once.
	for syntax := range wantOut {
		t.Errorf("no ast.Selection found with syntax %q", syntax)
	}
}

func TestIssue8518(t *testing.T) {
	fset := token.NewFileSet()
	conf := Config{
		Packages: make(map[string]*Package),
		Error:    func(err error) { t.Log(err) }, // don't exit after first error
		Import: func(imports map[string]*Package, path string) (*Package, error) {
			return imports[path], nil
		},
	}
	makePkg := func(path, src string) {
		f, err := parser.ParseFile(fset, path, src, 0)
		if err != nil {
			t.Fatal(err)
		}
		pkg, _ := conf.Check(path, fset, []*ast.File{f}, nil) // errors logged via conf.Error
		conf.Packages[path] = pkg
	}

	const libSrc = `
package a 
import "missing"
const C1 = foo
const C2 = missing.C
`

	const mainSrc = `
package main
import "a"
var _ = a.C1
var _ = a.C2
`

	makePkg("a", libSrc)
	makePkg("main", mainSrc) // don't crash when type-checking this package
}

func TestLookupFieldOrMethod(t *testing.T) {
	// Test cases assume a lookup of the form a.f or x.f, where a stands for an
	// addressable value, and x for a non-addressable value (even though a variable
	// for ease of test case writing).
	var tests = []struct {
		src      string
		found    bool
		index    []int
		indirect bool
	}{
		// field lookups
		{"var x T; type T struct{}", false, nil, false},
		{"var x T; type T struct{ f int }", true, []int{0}, false},
		{"var x T; type T struct{ a, b, f, c int }", true, []int{2}, false},

		// method lookups
		{"var a T; type T struct{}; func (T) f() {}", true, []int{0}, false},
		{"var a *T; type T struct{}; func (T) f() {}", true, []int{0}, true},
		{"var a T; type T struct{}; func (*T) f() {}", true, []int{0}, false},
		{"var a *T; type T struct{}; func (*T) f() {}", true, []int{0}, true}, // TODO(gri) should this report indirect = false?

		// collisions
		{"type ( E1 struct{ f int }; E2 struct{ f int }; x struct{ E1; *E2 })", false, []int{1, 0}, false},
		{"type ( E1 struct{ f int }; E2 struct{}; x struct{ E1; *E2 }); func (E2) f() {}", false, []int{1, 0}, false},

		// outside methodset
		// (*T).f method exists, but value of type T is not addressable
		{"var x T; type T struct{}; func (*T) f() {}", false, nil, true},
	}

	for _, test := range tests {
		pkg, err := pkgFor("test", "package p;"+test.src, nil)
		if err != nil {
			t.Errorf("%s: incorrect test case: %s", test.src, err)
			continue
		}

		obj := pkg.Scope().Lookup("a")
		if obj == nil {
			if obj = pkg.Scope().Lookup("x"); obj == nil {
				t.Errorf("%s: incorrect test case - no object a or x", test.src)
				continue
			}
		}

		f, index, indirect := LookupFieldOrMethod(obj.Type(), obj.Name() == "a", pkg, "f")
		if (f != nil) != test.found {
			if f == nil {
				t.Errorf("%s: got no object; want one", test.src)
			} else {
				t.Errorf("%s: got object = %v; want none", test.src, f)
			}
		}
		if !sameSlice(index, test.index) {
			t.Errorf("%s: got index = %v; want %v", test.src, index, test.index)
		}
		if indirect != test.indirect {
			t.Errorf("%s: got indirect = %v; want %v", test.src, indirect, test.indirect)
		}
	}
}

func sameSlice(a, b []int) bool {
	if len(a) != len(b) {
		return false
	}
	for i, x := range a {
		if x != b[i] {
			return false
		}
	}
	return true
}