func (p *exporter) field(f *types.Var) {
	if !f.IsField() {
		log.Fatalf("gcimporter: field expected")
	}

	p.pos(f)
	p.fieldName(f)
	p.typ(f.Type())
}

func (b *Builder) addVariable(u types.Universe, useName *types.Name, in *tc.Var) *types.Type {
	name := tcVarNameToName(in.String())
	if useName != nil {
		name = *useName
	}
	out := u.Variable(name)
	out.Kind = types.DeclarationOf
	out.Underlying = b.walkType(u, nil, in.Type())
	return out
}

func (g *ObjcGen) genSetter(oName string, f *types.Var) {
	t := f.Type()

	g.Printf("- (void)set%s:(%s)v {\n", f.Name(), g.objcType(t))
	g.Indent()
	g.Printf("int32_t refnum = go_seq_go_to_refnum(self._ref);\n")
	g.genWrite("v", f.Type(), modeRetained)
	g.Printf("proxy%s_%s_%s_Set(refnum, _v);\n", g.pkgPrefix, oName, f.Name())
	g.genRelease("v", f.Type(), modeRetained)
	g.Outdent()
	g.Printf("}\n\n")
}

func (g *ObjcGen) genGetter(oName string, f *types.Var) {
	t := f.Type()
	g.Printf("- (%s)%s {\n", g.objcType(t), objcNameReplacer(lowerFirst(f.Name())))
	g.Indent()
	g.Printf("int32_t refnum = go_seq_go_to_refnum(self._ref);\n")
	g.Printf("%s r0 = ", g.cgoType(f.Type()))
	g.Printf("proxy%s_%s_%s_Get(refnum);\n", g.pkgPrefix, oName, f.Name())
	g.genRead("_r0", "r0", f.Type(), modeRetained)
	g.Printf("return _r0;\n")
	g.Outdent()
	g.Printf("}\n\n")
}

func (g *javaGen) genVar(o *types.Var) {
	if t := o.Type(); !g.isSupported(t) {
		g.Printf("// skipped variable %s with unsupported type: %T\n\n", o.Name(), t)
		return
	}
	jType := g.javaType(o.Type())

	// setter
	g.Printf("public static native void set%s(%s v);\n", o.Name(), jType)

	// getter
	g.Printf("public static native %s get%s();\n\n", jType, o.Name())
}

func (c *funcContext) varPtrName(o *types.Var) string {
	if isPkgLevel(o) && o.Exported() {
		return c.pkgVar(o.Pkg()) + "." + o.Name() + "$ptr"
	}

	name, ok := c.p.varPtrNames[o]
	if !ok {
		name = c.newVariableWithLevel(o.Name()+"$ptr", isPkgLevel(o))
		c.p.varPtrNames[o] = name
	}
	return name
}

func (p *exporter) field(f *types.Var) {
	// anonymous fields have "" name
	name := ""
	if !f.Anonymous() {
		name = f.Name()
	}

	// qualifiedName will always emit the field package for
	// anonymous fields because "" is not an exported name.
	p.qualifiedName(f.Pkg(), name)
	p.typ(f.Type())
}

// fieldName is like qualifiedName but it doesn't record the package
// for blank (_) or exported names.
func (p *exporter) fieldName(f *types.Var) {
	name := f.Name()

	// anonymous field with unexported base type name: use "?" as field name
	// (bname != "" per spec, but we are conservative in case of errors)
	if f.Anonymous() {
		base := f.Type()
		if ptr, ok := base.(*types.Pointer); ok {
			base = ptr.Elem()
		}
		if named, ok := base.(*types.Named); ok && !named.Obj().Exported() {
			name = "?"
		}
	}

	p.string(name)
	if name == "?" || name != "_" && !f.Exported() {
		p.pkg(f.Pkg(), false)
	}
}

func (g *goGen) genVar(o *types.Var) {
	// TODO(hyangah): non-struct pointer types (*int), struct type.

	v := fmt.Sprintf("%s.%s", g.pkg.Name(), o.Name())

	// var I int
	//
	// func var_setI(out, in *seq.Buffer)
	g.Printf("func var_set%s(out, in *seq.Buffer) {\n", o.Name())
	g.Indent()
	g.genRead("v", "in", o.Type())
	g.Printf("%s = v\n", v)
	g.Outdent()
	g.Printf("}\n")

	// func var_getI(out, in *seq.Buffer)
	g.Printf("func var_get%s(out, in *seq.Buffer) {\n", o.Name())
	g.Indent()
	g.genWrite(v, "out", o.Type())
	g.Outdent()
	g.Printf("}\n")
}

func checkVarValue(t *testing.T, prog *ssa.Program, pkg *ssa.Package, ref []ast.Node, obj *types.Var, expKind string, wantAddr bool) {
	// The prefix of all assertions messages.
	prefix := fmt.Sprintf("VarValue(%s @ L%d)",
		obj, prog.Fset.Position(ref[0].Pos()).Line)

	v, gotAddr := prog.VarValue(obj, pkg, ref)

	// Kind is the concrete type of the ssa Value.
	gotKind := "nil"
	if v != nil {
		gotKind = fmt.Sprintf("%T", v)[len("*ssa."):]
	}

	// fmt.Printf("%s = %v (kind %q; expect %q) wantAddr=%t gotAddr=%t\n", prefix, v, gotKind, expKind, wantAddr, gotAddr) // debugging

	// Check the kinds match.
	// "nil" indicates expected failure (e.g. optimized away).
	if expKind != gotKind {
		t.Errorf("%s concrete type == %s, want %s", prefix, gotKind, expKind)
	}

	// Check the types match.
	// If wantAddr, the expected type is the object's address.
	if v != nil {
		expType := obj.Type()
		if wantAddr {
			expType = types.NewPointer(expType)
			if !gotAddr {
				t.Errorf("%s: got value, want address", prefix)
			}
		} else if gotAddr {
			t.Errorf("%s: got address, want value", prefix)
		}
		if !types.Identical(v.Type(), expType) {
			t.Errorf("%s.Type() == %s, want %s", prefix, v.Type(), expType)
		}
	}
}

// VarValue returns the SSA Value that corresponds to a specific
// identifier denoting the source-level named variable obj.
//
// VarValue returns nil if a local variable was not found, perhaps
// because its package was not built, the debug information was not
// requested during SSA construction, or the value was optimized away.
//
// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
// and that ident must resolve to obj.
//
// pkg is the package enclosing the reference.  (A reference to a var
// always occurs within a function, so we need to know where to find it.)
//
// If the identifier is a field selector and its base expression is
// non-addressable, then VarValue returns the value of that field.
// For example:
//    func f() struct {x int}
//    f().x  // VarValue(x) returns a *Field instruction of type int
//
// All other identifiers denote addressable locations (variables).
// For them, VarValue may return either the variable's address or its
// value, even when the expression is evaluated only for its value; the
// situation is reported by isAddr, the second component of the result.
//
// If !isAddr, the returned value is the one associated with the
// specific identifier.  For example,
//       var x int    // VarValue(x) returns Const 0 here
//       x = 1        // VarValue(x) returns Const 1 here
//
// It is not specified whether the value or the address is returned in
// any particular case, as it may depend upon optimizations performed
// during SSA code generation, such as registerization, constant
// folding, avoidance of materialization of subexpressions, etc.
//
func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) (value Value, isAddr bool) {
	// All references to a var are local to some function, possibly init.
	fn := EnclosingFunction(pkg, ref)
	if fn == nil {
		return // e.g. def of struct field; SSA not built?
	}

	id := ref[0].(*ast.Ident)

	// Defining ident of a parameter?
	if id.Pos() == obj.Pos() {
		for _, param := range fn.Params {
			if param.Object() == obj {
				return param, false
			}
		}
	}

	// Other ident?
	for _, b := range fn.Blocks {
		for _, instr := range b.Instrs {
			if dr, ok := instr.(*DebugRef); ok {
				if dr.Pos() == id.Pos() {
					return dr.X, dr.IsAddr
				}
			}
		}
	}

	// Defining ident of package-level var?
	if v := prog.packageLevelValue(obj); v != nil {
		return v.(*Global), true
	}

	return // e.g. debug info not requested, or var optimized away
}

func (tr *Transformer) matchWildcard(xobj *types.Var, y ast.Expr) bool {
	name := xobj.Name()

	if tr.verbose {
		fmt.Fprintf(os.Stderr, "%s: wildcard %s -> %s?: ",
			tr.fset.Position(y.Pos()), name, astString(tr.fset, y))
	}

	// Check that y is assignable to the declared type of the param.
	yt := tr.info.TypeOf(y)
	if yt == nil {
		// y has no type.
		// Perhaps it is an *ast.Ellipsis in [...]T{}, or
		// an *ast.KeyValueExpr in T{k: v}.
		// Clearly these pseudo-expressions cannot match a
		// wildcard, but it would nice if we had a way to ignore
		// the difference between T{v} and T{k:v} for structs.
		return false
	}
	if !types.AssignableTo(yt, xobj.Type()) {
		if tr.verbose {
			fmt.Fprintf(os.Stderr, "%s not assignable to %s\n", yt, xobj.Type())
		}
		return false
	}

	// A wildcard matches any expression.
	// If it appears multiple times in the pattern, it must match
	// the same expression each time.
	if old, ok := tr.env[name]; ok {
		// found existing binding
		tr.allowWildcards = false
		r := tr.matchExpr(old, y)
		if tr.verbose {
			fmt.Fprintf(os.Stderr, "%t secondary match, primary was %s\n",
				r, astString(tr.fset, old))
		}
		tr.allowWildcards = true
		return r
	}

	if tr.verbose {
		fmt.Fprintf(os.Stderr, "primary match\n")
	}

	tr.env[name] = y // record binding
	return true
}

func (c *converter) convertVar(v *gotypes.Var) *types.Var {
	if v == nil {
		return nil
	}
	if v, ok := c.converted[v]; ok {
		return v.(*types.Var)
	}
	ret := types.NewVar(
		token.Pos(v.Pos()),
		c.ret,
		v.Name(),
		c.convertType(v.Type()),
	)
	c.converted[v] = ret
	return ret
}

func (g *objcGen) genSetter(desc string, f *types.Var) {
	t := f.Type()
	if isErrorType(t) {
		t = types.Typ[types.String]
	}
	s := &funcSummary{
		name:   "set" + f.Name(),
		ret:    "void",
		params: []paramInfo{{typ: t, name: "v"}},
	}

	g.Printf("- %s {\n", s.asMethod(g))
	g.Indent()
	g.genFunc(desc+"_DESCRIPTOR_", desc+"_FIELD_"+f.Name()+"_SET_", s, true)
	g.Outdent()
	g.Printf("}\n\n")
}

func (g *objcGen) genGetter(desc string, f *types.Var) {
	t := f.Type()
	if isErrorType(t) {
		t = types.Typ[types.String]
	}
	s := &funcSummary{
		name:      lowerFirst(f.Name()),
		ret:       g.objcType(t),
		retParams: []paramInfo{{typ: t, name: "ret_"}},
	}

	g.Printf("- %s {\n", s.asMethod(g))
	g.Indent()
	g.genFunc(desc+"_DESCRIPTOR_", desc+"_FIELD_"+f.Name()+"_GET_", s, true)
	g.Outdent()
	g.Printf("}\n\n")
}

func (g *objcGen) genVarM(o *types.Var) {
	varDesc := fmt.Sprintf("%q", g.pkg.Name()+"."+o.Name())
	objcType := g.objcType(o.Type())

	// setter
	s1 := &funcSummary{
		name:   g.namePrefix + "_set" + o.Name(),
		ret:    "void",
		params: []paramInfo{{typ: o.Type(), name: "v"}},
	}
	g.Printf("void %s(%s v) {\n", s1.name, objcType)
	g.Indent()
	g.genFunc(varDesc, "1", s1, false)
	g.Outdent()
	g.Printf("}\n\n")

	// getter
	s2 := &funcSummary{
		name:      g.namePrefix + o.Name(),
		ret:       objcType,
		retParams: []paramInfo{{typ: o.Type(), name: "ret"}},
	}
	g.Printf("%s %s() {\n", s2.ret, s2.name)
	g.Indent()
	g.genFunc(varDesc, "2", s2, false)
	g.Outdent()
	g.Printf("}\n\n")
}

// makeWrapper returns a synthetic method that delegates to the
// declared method denoted by meth.Obj(), first performing any
// necessary pointer indirections or field selections implied by meth.
//
// The resulting method's receiver type is meth.Recv().
//
// This function is versatile but quite subtle!  Consider the
// following axes of variation when making changes:
//   - optional receiver indirection
//   - optional implicit field selections
//   - meth.Obj() may denote a concrete or an interface method
//   - the result may be a thunk or a wrapper.
//
// EXCLUSIVE_LOCKS_REQUIRED(prog.methodsMu)
//
func makeWrapper(prog *Program, sel *types.Selection) *Function {
	obj := sel.Obj().(*types.Func)       // the declared function
	sig := sel.Type().(*types.Signature) // type of this wrapper

	var recv *types.Var // wrapper's receiver or thunk's params[0]
	name := obj.Name()
	var description string
	var start int // first regular param
	if sel.Kind() == types.MethodExpr {
		name += "$thunk"
		description = "thunk"
		recv = sig.Params().At(0)
		start = 1
	} else {
		description = "wrapper"
		recv = sig.Recv()
	}

	description = fmt.Sprintf("%s for %s", description, sel.Obj())
	if prog.mode&LogSource != 0 {
		defer logStack("make %s to (%s)", description, recv.Type())()
	}
	fn := &Function{
		name:      name,
		method:    sel,
		object:    obj,
		Signature: sig,
		Synthetic: description,
		Prog:      prog,
		pos:       obj.Pos(),
	}
	fn.startBody()
	fn.addSpilledParam(recv)
	createParams(fn, start)

	indices := sel.Index()

	var v Value = fn.Locals[0] // spilled receiver
	if isPointer(sel.Recv()) {
		v = emitLoad(fn, v)

		// For simple indirection wrappers, perform an informative nil-check:
		// "value method (T).f called using nil *T pointer"
		if len(indices) == 1 && !isPointer(recvType(obj)) {
			var c Call
			c.Call.Value = &Builtin{
				name: "ssa:wrapnilchk",
				sig: types.NewSignature(nil,
					types.NewTuple(anonVar(sel.Recv()), anonVar(tString), anonVar(tString)),
					types.NewTuple(anonVar(sel.Recv())), false),
			}
			c.Call.Args = []Value{
				v,
				stringConst(deref(sel.Recv()).String()),
				stringConst(sel.Obj().Name()),
			}
			c.setType(v.Type())
			v = fn.emit(&c)
		}
	}

	// Invariant: v is a pointer, either
	//   value of *A receiver param, or
	// address of  A spilled receiver.

	// We use pointer arithmetic (FieldAddr possibly followed by
	// Load) in preference to value extraction (Field possibly
	// preceded by Load).

	v = emitImplicitSelections(fn, v, indices[:len(indices)-1])

	// Invariant: v is a pointer, either
	//   value of implicit *C field, or
	// address of implicit  C field.

	var c Call
	if r := recvType(obj); !isInterface(r) { // concrete method
		if !isPointer(r) {
			v = emitLoad(fn, v)
		}
		c.Call.Value = prog.declaredFunc(obj)
		c.Call.Args = append(c.Call.Args, v)
	} else {
		c.Call.Method = obj
		c.Call.Value = emitLoad(fn, v)
//.........这里部分代码省略.........

func (g *ObjcGen) genVarM(o *types.Var) {
	if t := o.Type(); !g.isSupported(t) {
		g.Printf("// skipped variable %s with unsupported type: %T\n\n", o.Name(), t)
		return
	}
	objcType := g.objcType(o.Type())

	// setter
	g.Printf("+ (void) set%s:(%s)v {\n", o.Name(), objcType)
	g.Indent()
	g.genWrite("v", o.Type(), modeRetained)
	g.Printf("var_set%s_%s(_v);\n", g.pkgPrefix, o.Name())
	g.genRelease("v", o.Type(), modeRetained)
	g.Outdent()
	g.Printf("}\n\n")

	// getter
	g.Printf("+ (%s) %s {\n", objcType, objcNameReplacer(lowerFirst(o.Name())))
	g.Indent()
	g.Printf("%s r0 = ", g.cgoType(o.Type()))
	g.Printf("var_get%s_%s();\n", g.pkgPrefix, o.Name())
	g.genRead("_r0", "r0", o.Type(), modeRetained)
	g.Printf("return _r0;\n")
	g.Outdent()
	g.Printf("}\n\n")
}

// checkStructField checks that the field renaming will not cause
// conflicts at its declaration, or ambiguity or changes to any selection.
func (r *renamer) checkStructField(from *types.Var) {
	// Check that the struct declaration is free of field conflicts,
	// and field/method conflicts.

	// go/types offers no easy way to get from a field (or interface
	// method) to its declaring struct (or interface), so we must
	// ascend the AST.
	info, path, _ := r.iprog.PathEnclosingInterval(from.Pos(), from.Pos())
	// path matches this pattern:
	// [Ident SelectorExpr? StarExpr? Field FieldList StructType ParenExpr* ... File]

	// Ascend to FieldList.
	var i int
	for {
		if _, ok := path[i].(*ast.FieldList); ok {
			break
		}
		i++
	}
	i++
	tStruct := path[i].(*ast.StructType)
	i++
	// Ascend past parens (unlikely).
	for {
		_, ok := path[i].(*ast.ParenExpr)
		if !ok {
			break
		}
		i++
	}
	if spec, ok := path[i].(*ast.TypeSpec); ok {
		// This struct is also a named type.
		// We must check for direct (non-promoted) field/field
		// and method/field conflicts.
		named := info.Defs[spec.Name].Type()
		prev, indices, _ := types.LookupFieldOrMethod(named, true, info.Pkg, r.to)
		if len(indices) == 1 {
			r.errorf(from.Pos(), "renaming this field %q to %q",
				from.Name(), r.to)
			r.errorf(prev.Pos(), "\twould conflict with this %s",
				objectKind(prev))
			return // skip checkSelections to avoid redundant errors
		}
	} else {
		// This struct is not a named type.
		// We need only check for direct (non-promoted) field/field conflicts.
		T := info.Types[tStruct].Type.Underlying().(*types.Struct)
		for i := 0; i < T.NumFields(); i++ {
			if prev := T.Field(i); prev.Name() == r.to {
				r.errorf(from.Pos(), "renaming this field %q to %q",
					from.Name(), r.to)
				r.errorf(prev.Pos(), "\twould conflict with this field")
				return // skip checkSelections to avoid redundant errors
			}
		}
	}

	// Renaming an anonymous field requires renaming the type too. e.g.
	// 	print(s.T)       // if we rename T to U,
	// 	type T int       // this and
	// 	var s struct {T} // this must change too.
	if from.Anonymous() {
		if named, ok := from.Type().(*types.Named); ok {
			r.check(named.Obj())
		} else if named, ok := deref(from.Type()).(*types.Named); ok {
			r.check(named.Obj())
		}
	}

	// Check integrity of existing (field and method) selections.
	r.checkSelections(from)
}

func (g *javaGen) genVar(o *types.Var) {
	jType := g.javaType(o.Type())
	varDesc := fmt.Sprintf("%s.%s", g.pkg.Name(), o.Name())

	// setter
	g.Printf("public static void set%s(%s v) {\n", o.Name(), jType)
	g.Indent()
	g.Printf("Seq in = new Seq();\n")
	g.Printf("Seq out = new Seq();\n")
	g.Printf("in.write%s;\n", seqWrite(o.Type(), "v"))
	g.Printf("Seq.send(%q, 1, in, out);\n", varDesc)
	g.Outdent()
	g.Printf("}\n")
	g.Printf("\n")

	// getter
	g.Printf("public static %s get%s() {\n", jType, o.Name())
	g.Indent()
	g.Printf("Seq in = new Seq();\n")
	g.Printf("Seq out = new Seq();\n")
	g.Printf("Seq.send(%q, 2, in, out);\n", varDesc)
	g.Printf("%s ", jType)
	g.genRead("v", "out", o.Type())
	g.Printf("return v;\n")
	g.Outdent()
	g.Printf("}\n")
	g.Printf("\n")
}