func (c *funcContext) zeroValue(ty types.Type) ast.Expr {
switch t := ty.Underlying().(type) {
case *types.Basic:
switch {
case isBoolean(t):
return c.newConst(ty, exact.MakeBool(false))
case isNumeric(t):
return c.newConst(ty, exact.MakeInt64(0))
case isString(t):
return c.newConst(ty, exact.MakeString(""))
case t.Kind() == types.UnsafePointer:
// fall through to "nil"
case t.Kind() == types.UntypedNil:
panic("Zero value for untyped nil.")
default:
panic(fmt.Sprintf("Unhandled basic type: %v\n", t))
}
case *types.Array, *types.Struct:
return c.setType(&ast.CompositeLit{}, ty)
case *types.Chan, *types.Interface, *types.Map, *types.Signature, *types.Slice, *types.Pointer:
// fall through to "nil"
default:
panic(fmt.Sprintf("Unhandled type: %T\n", t))
}
id := c.newIdent("nil", ty)
c.p.Uses[id] = nilObj
return id
}
// zeroConst returns a new "zero" constant of the specified type,
// which must not be an array or struct type: the zero values of
// aggregates are well-defined but cannot be represented by Const.
//
func zeroConst(t types.Type) *Const {
switch t := t.(type) {
case *types.Basic:
switch {
case t.Info()&types.IsBoolean != 0:
return NewConst(exact.MakeBool(false), t)
case t.Info()&types.IsNumeric != 0:
return NewConst(exact.MakeInt64(0), t)
case t.Info()&types.IsString != 0:
return NewConst(exact.MakeString(""), t)
case t.Kind() == types.UnsafePointer:
fallthrough
case t.Kind() == types.UntypedNil:
return nilConst(t)
default:
panic(fmt.Sprint("zeroConst for unexpected type:", t))
}
case *types.Pointer, *types.Slice, *types.Interface, *types.Chan, *types.Map, *types.Signature:
return nilConst(t)
case *types.Named:
return NewConst(zeroConst(t.Underlying()).Value, t)
case *types.Array, *types.Struct, *types.Tuple:
panic(fmt.Sprint("zeroConst applied to aggregate:", t))
}
panic(fmt.Sprint("zeroConst: unexpected ", t))
}
func (p *importer) value() exact.Value {
switch kind := exact.Kind(p.int()); kind {
case falseTag:
return exact.MakeBool(false)
case trueTag:
return exact.MakeBool(true)
case int64Tag:
return exact.MakeInt64(p.int64())
case floatTag:
return p.float()
case fractionTag:
return p.fraction()
case complexTag:
re := p.fraction()
im := p.fraction()
return exact.BinaryOp(re, token.ADD, exact.MakeImag(im))
case stringTag:
return exact.MakeString(p.string())
default:
panic(fmt.Sprintf("unexpected value kind %d", kind))
}
}
func (check *Checker) comparison(x, y *operand, op token.Token) {
// spec: "In any comparison, the first operand must be assignable
// to the type of the second operand, or vice versa."
err := ""
if x.assignableTo(check.conf, y.typ) || y.assignableTo(check.conf, x.typ) {
defined := false
switch op {
case token.EQL, token.NEQ:
// spec: "The equality operators == and != apply to operands that are comparable."
defined = Comparable(x.typ) || x.isNil() && hasNil(y.typ) || y.isNil() && hasNil(x.typ)
case token.LSS, token.LEQ, token.GTR, token.GEQ:
// spec: The ordering operators <, <=, >, and >= apply to operands that are ordered."
defined = isOrdered(x.typ)
default:
unreachable()
}
if !defined {
typ := x.typ
if x.isNil() {
typ = y.typ
}
err = check.sprintf("operator %s not defined for %s", op, typ)
}
} else {
err = check.sprintf("mismatched types %s and %s", x.typ, y.typ)
}
if err != "" {
check.errorf(x.pos(), "cannot compare %s %s %s (%s)", x.expr, op, y.expr, err)
x.mode = invalid
return
}
if x.mode == constant && y.mode == constant {
x.val = exact.MakeBool(exact.Compare(x.val, op, y.val))
// The operands are never materialized; no need to update
// their types.
} else {
x.mode = value
// The operands have now their final types, which at run-
// time will be materialized. Update the expression trees.
// If the current types are untyped, the materialized type
// is the respective default type.
check.updateExprType(x.expr, defaultType(x.typ), true)
check.updateExprType(y.expr, defaultType(y.typ), true)
}
// spec: "Comparison operators compare two operands and yield
// an untyped boolean value."
x.typ = Typ[UntypedBool]
}
func (c *funcContext) translateStmt(stmt ast.Stmt, label *types.Label) {
c.SetPos(stmt.Pos())
stmt = filter.IncDecStmt(stmt, c.p.Info)
stmt = filter.Assign(stmt, c.p.Info)
switch s := stmt.(type) {
case *ast.BlockStmt:
c.translateStmtList(s.List)
case *ast.IfStmt:
if s.Init != nil {
c.translateStmt(s.Init, nil)
}
var caseClauses []ast.Stmt
ifStmt := s
for {
caseClauses = append(caseClauses, &ast.CaseClause{List: []ast.Expr{ifStmt.Cond}, Body: ifStmt.Body.List})
switch elseStmt := ifStmt.Else.(type) {
case *ast.IfStmt:
if elseStmt.Init != nil {
caseClauses = append(caseClauses, &ast.CaseClause{List: nil, Body: []ast.Stmt{elseStmt}})
break
}
ifStmt = elseStmt
continue
case *ast.BlockStmt:
caseClauses = append(caseClauses, &ast.CaseClause{List: nil, Body: elseStmt.List})
case *ast.EmptyStmt, nil:
// no else clause
default:
panic(fmt.Sprintf("Unhandled else: %T\n", elseStmt))
}
break
}
c.translateBranchingStmt(caseClauses, false, nil, nil, nil, c.Flattened[s])
case *ast.SwitchStmt:
if s.Init != nil {
c.translateStmt(s.Init, nil)
}
tag := s.Tag
if tag == nil {
tag = ast.NewIdent("true")
c.p.Types[tag] = types.TypeAndValue{Type: types.Typ[types.Bool], Value: exact.MakeBool(true)}
}
if c.p.Types[tag].Value == nil {
refVar := c.newVariable("_ref")
c.Printf("%s = %s;", refVar, c.translateExpr(tag))
tag = c.newIdent(refVar, c.p.Types[tag].Type)
}
translateCond := func(cond ast.Expr) *expression {
return c.translateExpr(&ast.BinaryExpr{
X: tag,
Op: token.EQL,
Y: cond,
})
}
c.translateBranchingStmt(s.Body.List, true, translateCond, nil, label, c.Flattened[s])
case *ast.TypeSwitchStmt:
if s.Init != nil {
c.translateStmt(s.Init, nil)
}
refVar := c.newVariable("_ref")
var expr ast.Expr
var printCaseBodyPrefix func(index int)
switch a := s.Assign.(type) {
case *ast.AssignStmt:
expr = a.Rhs[0].(*ast.TypeAssertExpr).X
printCaseBodyPrefix = func(index int) {
value := refVar
caseClause := s.Body.List[index].(*ast.CaseClause)
if len(caseClause.List) == 1 {
t := c.p.Types[caseClause.List[0]].Type
if _, isInterface := t.Underlying().(*types.Interface); !isInterface && !types.Identical(t, types.Typ[types.UntypedNil]) {
value += ".$val"
}
}
c.Printf("%s = %s;", c.objectName(c.p.Implicits[caseClause]), value)
}
case *ast.ExprStmt:
expr = a.X.(*ast.TypeAssertExpr).X
}
c.Printf("%s = %s;", refVar, c.translateExpr(expr))
translateCond := func(cond ast.Expr) *expression {
if types.Identical(c.p.Types[cond].Type, types.Typ[types.UntypedNil]) {
return c.formatExpr("%s === $ifaceNil", refVar)
}
return c.formatExpr("$assertType(%s, %s, true)[1]", refVar, c.typeName(c.p.Types[cond].Type))
}
c.translateBranchingStmt(s.Body.List, true, translateCond, printCaseBodyPrefix, label, c.Flattened[s])
case *ast.ForStmt:
if s.Init != nil {
c.translateStmt(s.Init, nil)
}
cond := func() string {
if s.Cond == nil {
return "true"
}
return c.translateExpr(s.Cond).String()
}
c.translateLoopingStmt(cond, s.Body, nil, func() {
if s.Post != nil {
c.translateStmt(s.Post, nil)
}
}, label, c.Flattened[s])
case *ast.RangeStmt:
refVar := c.newVariable("_ref")
c.Printf("%s = %s;", refVar, c.translateExpr(s.X))
switch t := c.p.Types[s.X].Type.Underlying().(type) {
case *types.Basic:
iVar := c.newVariable("_i")
c.Printf("%s = 0;", iVar)
runeVar := c.newVariable("_rune")
c.translateLoopingStmt(func() string { return iVar + " < " + refVar + ".length" }, s.Body, func() {
c.Printf("%s = $decodeRune(%s, %s);", runeVar, refVar, iVar)
if !isBlank(s.Key) {
c.Printf("%s", c.translateAssign(s.Key, iVar, types.Typ[types.Int], s.Tok == token.DEFINE))
}
if !isBlank(s.Value) {
c.Printf("%s", c.translateAssign(s.Value, runeVar+"[0]", types.Typ[types.Rune], s.Tok == token.DEFINE))
}
}, func() {
c.Printf("%s += %s[1];", iVar, runeVar)
}, label, c.Flattened[s])
case *types.Map:
iVar := c.newVariable("_i")
c.Printf("%s = 0;", iVar)
keysVar := c.newVariable("_keys")
c.Printf("%s = $keys(%s);", keysVar, refVar)
c.translateLoopingStmt(func() string { return iVar + " < " + keysVar + ".length" }, s.Body, func() {
entryVar := c.newVariable("_entry")
c.Printf("%s = %s[%s[%s]];", entryVar, refVar, keysVar, iVar)
c.translateStmt(&ast.IfStmt{
Cond: c.newIdent(entryVar+" === undefined", types.Typ[types.Bool]),
Body: &ast.BlockStmt{List: []ast.Stmt{&ast.BranchStmt{Tok: token.CONTINUE}}},
}, nil)
if !isBlank(s.Key) {
c.Printf("%s", c.translateAssign(s.Key, entryVar+".k", t.Key(), s.Tok == token.DEFINE))
}
if !isBlank(s.Value) {
c.Printf("%s", c.translateAssign(s.Value, entryVar+".v", t.Elem(), s.Tok == token.DEFINE))
}
}, func() {
c.Printf("%s++;", iVar)
}, label, c.Flattened[s])
case *types.Array, *types.Pointer, *types.Slice:
var length string
var elemType types.Type
switch t2 := t.(type) {
case *types.Array:
length = fmt.Sprintf("%d", t2.Len())
elemType = t2.Elem()
case *types.Pointer:
length = fmt.Sprintf("%d", t2.Elem().Underlying().(*types.Array).Len())
elemType = t2.Elem().Underlying().(*types.Array).Elem()
case *types.Slice:
length = refVar + ".$length"
elemType = t2.Elem()
}
iVar := c.newVariable("_i")
c.Printf("%s = 0;", iVar)
c.translateLoopingStmt(func() string { return iVar + " < " + length }, s.Body, func() {
if !isBlank(s.Key) {
c.Printf("%s", c.translateAssign(s.Key, iVar, types.Typ[types.Int], s.Tok == token.DEFINE))
}
if !isBlank(s.Value) {
c.Printf("%s", c.translateAssign(s.Value, c.translateImplicitConversion(c.setType(&ast.IndexExpr{
X: c.newIdent(refVar, t),
Index: c.newIdent(iVar, types.Typ[types.Int]),
}, elemType), elemType).String(), elemType, s.Tok == token.DEFINE))
}
}, func() {
c.Printf("%s++;", iVar)
}, label, c.Flattened[s])
case *types.Chan:
okVar := c.newIdent(c.newVariable("_ok"), types.Typ[types.Bool])
key := s.Key
tok := s.Tok
if key == nil {
key = ast.NewIdent("_")
tok = token.ASSIGN
}
forStmt := &ast.ForStmt{
Body: &ast.BlockStmt{
List: []ast.Stmt{
&ast.AssignStmt{
Lhs: []ast.Expr{
key,
okVar,
},
Rhs: []ast.Expr{
c.setType(&ast.UnaryExpr{X: c.newIdent(refVar, t), Op: token.ARROW}, types.NewTuple(types.NewVar(0, nil, "", t.Elem()), types.NewVar(0, nil, "", types.Typ[types.Bool]))),
},
Tok: tok,
},
&ast.IfStmt{
Cond: &ast.UnaryExpr{X: okVar, Op: token.NOT},
Body: &ast.BlockStmt{List: []ast.Stmt{&ast.BranchStmt{Tok: token.BREAK}}},
},
s.Body,
},
},
}
c.Flattened[forStmt] = true
c.translateStmt(forStmt, label)
default:
panic("")
}
case *ast.BranchStmt:
normalLabel := ""
blockingLabel := ""
data := c.flowDatas[nil]
if s.Label != nil {
normalLabel = " " + s.Label.Name
blockingLabel = " s" // use explicit label "s", because surrounding loop may not be flattened
data = c.flowDatas[c.p.Uses[s.Label].(*types.Label)]
}
switch s.Tok {
case token.BREAK:
c.PrintCond(data.endCase == 0, fmt.Sprintf("break%s;", normalLabel), fmt.Sprintf("$s = %d; continue%s;", data.endCase, blockingLabel))
case token.CONTINUE:
data.postStmt()
c.PrintCond(data.beginCase == 0, fmt.Sprintf("continue%s;", normalLabel), fmt.Sprintf("$s = %d; continue%s;", data.beginCase, blockingLabel))
case token.GOTO:
c.PrintCond(false, "goto "+s.Label.Name, fmt.Sprintf("$s = %d; continue;", c.labelCase(c.p.Uses[s.Label].(*types.Label))))
case token.FALLTHROUGH:
// handled in CaseClause
default:
panic("Unhandled branch statment: " + s.Tok.String())
}
case *ast.ReturnStmt:
results := s.Results
if c.resultNames != nil {
if len(s.Results) != 0 {
c.translateStmt(&ast.AssignStmt{
Lhs: c.resultNames,
Tok: token.ASSIGN,
Rhs: s.Results,
}, nil)
}
results = c.resultNames
}
c.Printf("return%s;", c.translateResults(results))
case *ast.DeferStmt:
isBuiltin := false
isJs := false
switch fun := s.Call.Fun.(type) {
case *ast.Ident:
var builtin *types.Builtin
builtin, isBuiltin = c.p.Uses[fun].(*types.Builtin)
if isBuiltin && builtin.Name() == "recover" {
c.Printf("$deferred.push([$recover, []]);")
return
}
case *ast.SelectorExpr:
isJs = typesutil.IsJsPackage(c.p.Uses[fun.Sel].Pkg())
}
sig := c.p.Types[s.Call.Fun].Type.Underlying().(*types.Signature)
args := c.translateArgs(sig, s.Call.Args, s.Call.Ellipsis.IsValid(), true)
if isBuiltin || isJs {
vars := make([]string, len(s.Call.Args))
callArgs := make([]ast.Expr, len(s.Call.Args))
for i, arg := range s.Call.Args {
v := c.newVariable("_arg")
vars[i] = v
callArgs[i] = c.newIdent(v, c.p.Types[arg].Type)
}
call := c.translateExpr(&ast.CallExpr{
Fun: s.Call.Fun,
Args: callArgs,
Ellipsis: s.Call.Ellipsis,
})
c.Printf("$deferred.push([function(%s) { %s; }, [%s]]);", strings.Join(vars, ", "), call, strings.Join(args, ", "))
return
}
c.Printf("$deferred.push([%s, [%s]]);", c.translateExpr(s.Call.Fun), strings.Join(args, ", "))
case *ast.AssignStmt:
if s.Tok != token.ASSIGN && s.Tok != token.DEFINE {
panic(s.Tok)
}
if s.Tok == token.DEFINE {
for _, lhs := range s.Lhs {
if !isBlank(lhs) {
obj := c.p.Defs[lhs.(*ast.Ident)]
if obj == nil {
obj = c.p.Uses[lhs.(*ast.Ident)]
}
c.setType(lhs, obj.Type())
}
}
}
switch {
case len(s.Lhs) == 1 && len(s.Rhs) == 1:
lhs := astutil.RemoveParens(s.Lhs[0])
if isBlank(lhs) {
if analysis.HasSideEffect(s.Rhs[0], c.p.Info.Info) {
c.Printf("%s;", c.translateExpr(s.Rhs[0]).String())
}
return
}
lhsType := c.p.Types[s.Lhs[0]].Type
c.Printf("%s", c.translateAssignOfExpr(lhs, s.Rhs[0], lhsType, s.Tok == token.DEFINE))
case len(s.Lhs) > 1 && len(s.Rhs) == 1:
tupleVar := c.newVariable("_tuple")
out := tupleVar + " = " + c.translateExpr(s.Rhs[0]).String() + ";"
tuple := c.p.Types[s.Rhs[0]].Type.(*types.Tuple)
for i, lhs := range s.Lhs {
lhs = astutil.RemoveParens(lhs)
if !isBlank(lhs) {
lhsType := c.p.Types[s.Lhs[i]].Type
out += " " + c.translateAssignOfExpr(lhs, c.newIdent(fmt.Sprintf("%s[%d]", tupleVar, i), tuple.At(i).Type()), lhsType, s.Tok == token.DEFINE)
}
}
c.Printf("%s", out)
case len(s.Lhs) == len(s.Rhs):
tmpVars := make([]string, len(s.Rhs))
var parts []string
for i, rhs := range s.Rhs {
tmpVars[i] = c.newVariable("_tmp")
if isBlank(astutil.RemoveParens(s.Lhs[i])) {
if analysis.HasSideEffect(rhs, c.p.Info.Info) {
c.Printf("%s;", c.translateExpr(rhs).String())
}
continue
}
lhsType := c.p.Types[s.Lhs[i]].Type
parts = append(parts, c.translateAssignOfExpr(c.newIdent(tmpVars[i], c.p.Types[s.Lhs[i]].Type), rhs, lhsType, true))
}
for i, lhs := range s.Lhs {
lhs = astutil.RemoveParens(lhs)
if !isBlank(lhs) {
t := c.p.Types[lhs].Type
parts = append(parts, c.translateAssignOfExpr(lhs, c.newIdent(tmpVars[i], t), t, s.Tok == token.DEFINE))
}
}
c.Printf("%s", strings.Join(parts, " "))
default:
panic("Invalid arity of AssignStmt.")
}
case *ast.DeclStmt:
decl := s.Decl.(*ast.GenDecl)
switch decl.Tok {
case token.VAR:
for _, spec := range s.Decl.(*ast.GenDecl).Specs {
valueSpec := spec.(*ast.ValueSpec)
lhs := make([]ast.Expr, len(valueSpec.Names))
for i, name := range valueSpec.Names {
lhs[i] = name
}
rhs := valueSpec.Values
isTuple := false
if len(rhs) == 1 {
_, isTuple = c.p.Types[rhs[0]].Type.(*types.Tuple)
}
for len(rhs) < len(lhs) && !isTuple {
rhs = append(rhs, nil)
}
c.translateStmt(&ast.AssignStmt{
Lhs: lhs,
Tok: token.DEFINE,
Rhs: rhs,
}, nil)
}
case token.TYPE:
for _, spec := range decl.Specs {
o := c.p.Defs[spec.(*ast.TypeSpec).Name].(*types.TypeName)
c.p.typeNames = append(c.p.typeNames, o)
c.p.objectNames[o] = c.newVariableWithLevel(o.Name(), true)
c.p.dependencies[o] = true
}
case token.CONST:
// skip, constants are inlined
}
case *ast.ExprStmt:
expr := c.translateExpr(s.X)
if expr != nil && expr.String() != "" {
c.Printf("%s;", expr)
}
case *ast.LabeledStmt:
label := c.p.Defs[s.Label].(*types.Label)
if c.GotoLabel[label] {
c.PrintCond(false, s.Label.Name+":", fmt.Sprintf("case %d:", c.labelCase(label)))
}
c.translateStmt(s.Stmt, label)
case *ast.GoStmt:
c.Printf("$go(%s, [%s]);", c.translateExpr(s.Call.Fun), strings.Join(c.translateArgs(c.p.Types[s.Call.Fun].Type.Underlying().(*types.Signature), s.Call.Args, s.Call.Ellipsis.IsValid(), false), ", "))
case *ast.SendStmt:
chanType := c.p.Types[s.Chan].Type.Underlying().(*types.Chan)
call := &ast.CallExpr{
Fun: c.newIdent("$send", types.NewSignature(nil, types.NewTuple(types.NewVar(0, nil, "", chanType), types.NewVar(0, nil, "", chanType.Elem())), nil, false)),
Args: []ast.Expr{s.Chan, s.Value},
}
c.Blocking[call] = true
c.translateStmt(&ast.ExprStmt{X: call}, label)
case *ast.SelectStmt:
var channels []string
var caseClauses []ast.Stmt
flattened := false
hasDefault := false
for i, s := range s.Body.List {
clause := s.(*ast.CommClause)
switch comm := clause.Comm.(type) {
case nil:
channels = append(channels, "[]")
hasDefault = true
case *ast.ExprStmt:
channels = append(channels, c.formatExpr("[%e]", astutil.RemoveParens(comm.X).(*ast.UnaryExpr).X).String())
case *ast.AssignStmt:
channels = append(channels, c.formatExpr("[%e]", astutil.RemoveParens(comm.Rhs[0]).(*ast.UnaryExpr).X).String())
case *ast.SendStmt:
channels = append(channels, c.formatExpr("[%e, %e]", comm.Chan, comm.Value).String())
default:
panic(fmt.Sprintf("unhandled: %T", comm))
}
indexLit := &ast.BasicLit{Kind: token.INT}
c.p.Types[indexLit] = types.TypeAndValue{Type: types.Typ[types.Int], Value: exact.MakeInt64(int64(i))}
caseClauses = append(caseClauses, &ast.CaseClause{
List: []ast.Expr{indexLit},
Body: clause.Body,
})
flattened = flattened || c.Flattened[clause]
}
selectCall := c.setType(&ast.CallExpr{
Fun: c.newIdent("$select", types.NewSignature(nil, types.NewTuple(types.NewVar(0, nil, "", types.NewInterface(nil, nil))), types.NewTuple(types.NewVar(0, nil, "", types.Typ[types.Int])), false)),
Args: []ast.Expr{c.newIdent(fmt.Sprintf("[%s]", strings.Join(channels, ", ")), types.NewInterface(nil, nil))},
}, types.Typ[types.Int])
c.Blocking[selectCall] = !hasDefault
selectionVar := c.newVariable("_selection")
c.Printf("%s = %s;", selectionVar, c.translateExpr(selectCall))
translateCond := func(cond ast.Expr) *expression {
return c.formatExpr("%s[0] === %e", selectionVar, cond)
}
printCaseBodyPrefix := func(index int) {
if assign, ok := s.Body.List[index].(*ast.CommClause).Comm.(*ast.AssignStmt); ok {
switch rhsType := c.p.Types[assign.Rhs[0]].Type.(type) {
case *types.Tuple:
c.translateStmt(&ast.AssignStmt{Lhs: assign.Lhs, Rhs: []ast.Expr{c.newIdent(selectionVar+"[1]", rhsType)}, Tok: assign.Tok}, nil)
default:
c.translateStmt(&ast.AssignStmt{Lhs: assign.Lhs, Rhs: []ast.Expr{c.newIdent(selectionVar+"[1][0]", rhsType)}, Tok: assign.Tok}, nil)
}
}
}
c.translateBranchingStmt(caseClauses, true, translateCond, printCaseBodyPrefix, label, flattened)
case *ast.EmptyStmt:
// skip
default:
panic(fmt.Sprintf("Unhandled statement: %T\n", s))
}
}
// stmt typechecks statement s.
func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
// statements cannot use iota in general
// (constant declarations set it explicitly)
assert(check.iota == nil)
// statements must end with the same top scope as they started with
if debug {
defer func(scope *Scope) {
// don't check if code is panicking
if p := recover(); p != nil {
panic(p)
}
assert(scope == check.scope)
}(check.scope)
}
inner := ctxt &^ fallthroughOk
switch s := s.(type) {
case *ast.BadStmt, *ast.EmptyStmt:
// ignore
case *ast.DeclStmt:
check.declStmt(s.Decl)
case *ast.LabeledStmt:
check.hasLabel = true
check.stmt(ctxt, s.Stmt)
case *ast.ExprStmt:
// spec: "With the exception of specific built-in functions,
// function and method calls and receive operations can appear
// in statement context. Such statements may be parenthesized."
var x operand
kind := check.rawExpr(&x, s.X, nil)
var msg string
switch x.mode {
default:
if kind == statement {
return
}
msg = "is not used"
case builtin:
msg = "must be called"
case typexpr:
msg = "is not an expression"
}
check.errorf(x.pos(), "%s %s", &x, msg)
case *ast.SendStmt:
var ch, x operand
check.expr(&ch, s.Chan)
check.expr(&x, s.Value)
if ch.mode == invalid || x.mode == invalid {
return
}
if tch, ok := ch.typ.Underlying().(*Chan); !ok || tch.dir == RecvOnly || !check.assignment(&x, tch.elem) {
if x.mode != invalid {
check.invalidOp(ch.pos(), "cannot send %s to channel %s", &x, &ch)
}
}
case *ast.IncDecStmt:
var op token.Token
switch s.Tok {
case token.INC:
op = token.ADD
case token.DEC:
op = token.SUB
default:
check.invalidAST(s.TokPos, "unknown inc/dec operation %s", s.Tok)
return
}
var x operand
Y := &ast.BasicLit{ValuePos: s.X.Pos(), Kind: token.INT, Value: "1"} // use x's position
check.binary(&x, s.X, Y, op)
if x.mode == invalid {
return
}
check.assignVar(s.X, &x)
case *ast.AssignStmt:
switch s.Tok {
case token.ASSIGN, token.DEFINE:
if len(s.Lhs) == 0 {
check.invalidAST(s.Pos(), "missing lhs in assignment")
return
}
if s.Tok == token.DEFINE {
check.shortVarDecl(s.TokPos, s.Lhs, s.Rhs)
} else {
// regular assignment
check.assignVars(s.Lhs, s.Rhs)
}
default:
// assignment operations
if len(s.Lhs) != 1 || len(s.Rhs) != 1 {
check.errorf(s.TokPos, "assignment operation %s requires single-valued expressions", s.Tok)
return
}
op := assignOp(s.Tok)
if op == token.ILLEGAL {
check.invalidAST(s.TokPos, "unknown assignment operation %s", s.Tok)
return
}
var x operand
check.binary(&x, s.Lhs[0], s.Rhs[0], op)
if x.mode == invalid {
return
}
check.assignVar(s.Lhs[0], &x)
}
case *ast.GoStmt:
check.suspendedCall("go", s.Call)
case *ast.DeferStmt:
check.suspendedCall("defer", s.Call)
case *ast.ReturnStmt:
res := check.sig.results
if res.Len() > 0 {
// function returns results
// (if one, say the first, result parameter is named, all of them are named)
if len(s.Results) == 0 && res.vars[0].name != "" {
// spec: "Implementation restriction: A compiler may disallow an empty expression
// list in a "return" statement if a different entity (constant, type, or variable)
// with the same name as a result parameter is in scope at the place of the return."
for _, obj := range res.vars {
if _, alt := check.scope.LookupParent(obj.name); alt != nil && alt != obj {
check.errorf(s.Pos(), "result parameter %s not in scope at return", obj.name)
check.errorf(alt.Pos(), "\tinner declaration of %s", obj)
// ok to continue
}
}
} else {
// return has results or result parameters are unnamed
check.initVars(res.vars, s.Results, s.Return)
}
} else if len(s.Results) > 0 {
check.error(s.Results[0].Pos(), "no result values expected")
check.use(s.Results...)
}
case *ast.BranchStmt:
if s.Label != nil {
check.hasLabel = true
return // checked in 2nd pass (check.labels)
}
switch s.Tok {
case token.BREAK:
if ctxt&breakOk == 0 {
check.error(s.Pos(), "break not in for, switch, or select statement")
}
case token.CONTINUE:
if ctxt&continueOk == 0 {
check.error(s.Pos(), "continue not in for statement")
}
case token.FALLTHROUGH:
if ctxt&fallthroughOk == 0 {
check.error(s.Pos(), "fallthrough statement out of place")
}
default:
check.invalidAST(s.Pos(), "branch statement: %s", s.Tok)
}
case *ast.BlockStmt:
check.openScope(s, "block")
defer check.closeScope()
check.stmtList(inner, s.List)
case *ast.IfStmt:
check.openScope(s, "if")
defer check.closeScope()
check.simpleStmt(s.Init)
var x operand
check.expr(&x, s.Cond)
if x.mode != invalid && !isBoolean(x.typ) {
check.error(s.Cond.Pos(), "non-boolean condition in if statement")
}
check.stmt(inner, s.Body)
if s.Else != nil {
check.stmt(inner, s.Else)
}
case *ast.SwitchStmt:
inner |= breakOk
check.openScope(s, "switch")
defer check.closeScope()
check.simpleStmt(s.Init)
var x operand
if s.Tag != nil {
check.expr(&x, s.Tag)
} else {
// spec: "A missing switch expression is
// equivalent to the boolean value true."
x.mode = constant
x.typ = Typ[Bool]
x.val = exact.MakeBool(true)
x.expr = &ast.Ident{NamePos: s.Body.Lbrace, Name: "true"}
}
check.multipleDefaults(s.Body.List)
for i, c := range s.Body.List {
clause, _ := c.(*ast.CaseClause)
if clause == nil {
check.invalidAST(c.Pos(), "incorrect expression switch case")
continue
}
if x.mode != invalid {
check.caseValues(x, clause.List)
}
check.openScope(clause, "case")
inner := inner
if i+1 < len(s.Body.List) {
inner |= fallthroughOk
}
check.stmtList(inner, clause.Body)
check.closeScope()
}
case *ast.TypeSwitchStmt:
inner |= breakOk
check.openScope(s, "type switch")
defer check.closeScope()
check.simpleStmt(s.Init)
// A type switch guard must be of the form:
//
// TypeSwitchGuard = [ identifier ":=" ] PrimaryExpr "." "(" "type" ")" .
//
// The parser is checking syntactic correctness;
// remaining syntactic errors are considered AST errors here.
// TODO(gri) better factoring of error handling (invalid ASTs)
//
var lhs *ast.Ident // lhs identifier or nil
var rhs ast.Expr
switch guard := s.Assign.(type) {
case *ast.ExprStmt:
rhs = guard.X
case *ast.AssignStmt:
if len(guard.Lhs) != 1 || guard.Tok != token.DEFINE || len(guard.Rhs) != 1 {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
lhs, _ = guard.Lhs[0].(*ast.Ident)
if lhs == nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
check.recordDef(lhs, nil) // lhs variable is implicitly declared in each cause clause
rhs = guard.Rhs[0]
default:
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
// rhs must be of the form: expr.(type) and expr must be an interface
expr, _ := rhs.(*ast.TypeAssertExpr)
if expr == nil || expr.Type != nil {
check.invalidAST(s.Pos(), "incorrect form of type switch guard")
return
}
var x operand
check.expr(&x, expr.X)
if x.mode == invalid {
return
}
xtyp, _ := x.typ.Underlying().(*Interface)
if xtyp == nil {
check.errorf(x.pos(), "%s is not an interface", &x)
return
}
check.multipleDefaults(s.Body.List)
var lhsVars []*Var // list of implicitly declared lhs variables
seen := make(map[Type]token.Pos) // map of seen types to positions
for _, s := range s.Body.List {
clause, _ := s.(*ast.CaseClause)
if clause == nil {
check.invalidAST(s.Pos(), "incorrect type switch case")
continue
}
// Check each type in this type switch case.
T := check.caseTypes(&x, xtyp, clause.List, seen)
check.openScope(clause, "case")
// If lhs exists, declare a corresponding variable in the case-local scope.
if lhs != nil {
// spec: "The TypeSwitchGuard may include a short variable declaration.
// When that form is used, the variable is declared at the beginning of
// the implicit block in each clause. In clauses with a case listing
// exactly one type, the variable has that type; otherwise, the variable
// has the type of the expression in the TypeSwitchGuard."
if len(clause.List) != 1 || T == nil {
T = x.typ
}
obj := NewVar(lhs.Pos(), check.pkg, lhs.Name, T)
check.declare(check.scope, nil, obj)
check.recordImplicit(clause, obj)
// For the "declared but not used" error, all lhs variables act as
// one; i.e., if any one of them is 'used', all of them are 'used'.
// Collect them for later analysis.
lhsVars = append(lhsVars, obj)
}
check.stmtList(inner, clause.Body)
check.closeScope()
}
// If lhs exists, we must have at least one lhs variable that was used.
if lhs != nil {
var used bool
for _, v := range lhsVars {
if v.used {
used = true
}
v.used = true // avoid usage error when checking entire function
}
if !used {
check.softErrorf(lhs.Pos(), "%s declared but not used", lhs.Name)
}
}
case *ast.SelectStmt:
inner |= breakOk
check.multipleDefaults(s.Body.List)
for _, s := range s.Body.List {
clause, _ := s.(*ast.CommClause)
if clause == nil {
continue // error reported before
}
// clause.Comm must be a SendStmt, RecvStmt, or default case
valid := false
var rhs ast.Expr // rhs of RecvStmt, or nil
switch s := clause.Comm.(type) {
case nil, *ast.SendStmt:
valid = true
case *ast.AssignStmt:
if len(s.Rhs) == 1 {
rhs = s.Rhs[0]
}
case *ast.ExprStmt:
rhs = s.X
}
// if present, rhs must be a receive operation
if rhs != nil {
if x, _ := unparen(rhs).(*ast.UnaryExpr); x != nil && x.Op == token.ARROW {
valid = true
}
}
if !valid {
check.error(clause.Comm.Pos(), "select case must be send or receive (possibly with assignment)")
continue
}
check.openScope(s, "case")
defer check.closeScope()
if clause.Comm != nil {
check.stmt(inner, clause.Comm)
}
check.stmtList(inner, clause.Body)
}
case *ast.ForStmt:
inner |= breakOk | continueOk
check.openScope(s, "for")
defer check.closeScope()
check.simpleStmt(s.Init)
if s.Cond != nil {
var x operand
check.expr(&x, s.Cond)
if x.mode != invalid && !isBoolean(x.typ) {
check.error(s.Cond.Pos(), "non-boolean condition in for statement")
}
}
check.simpleStmt(s.Post)
// spec: "The init statement may be a short variable
// declaration, but the post statement must not."
if s, _ := s.Post.(*ast.AssignStmt); s != nil && s.Tok == token.DEFINE {
check.softErrorf(s.Pos(), "cannot declare in post statement")
check.use(s.Lhs...) // avoid follow-up errors
}
check.stmt(inner, s.Body)
case *ast.RangeStmt:
inner |= breakOk | continueOk
check.openScope(s, "for")
defer check.closeScope()
// check expression to iterate over
decl := s.Tok == token.DEFINE
var x operand
check.expr(&x, s.X)
if x.mode == invalid {
// if we don't have a declaration, we can still check the loop's body
// (otherwise we can't because we are missing the declared variables)
if !decl {
check.stmt(inner, s.Body)
}
return
}
// determine key/value types
var key, val Type
switch typ := x.typ.Underlying().(type) {
case *Basic:
if isString(typ) {
key = Typ[Int]
val = UniverseRune // use 'rune' name
}
case *Array:
key = Typ[Int]
val = typ.elem
case *Slice:
key = Typ[Int]
val = typ.elem
case *Pointer:
if typ, _ := typ.base.Underlying().(*Array); typ != nil {
key = Typ[Int]
val = typ.elem
}
case *Map:
key = typ.key
val = typ.elem
case *Chan:
key = typ.elem
val = Typ[Invalid]
if typ.dir == SendOnly {
check.errorf(x.pos(), "cannot range over send-only channel %s", &x)
// ok to continue
}
if s.Value != nil {
check.errorf(s.Value.Pos(), "iteration over %s permits only one iteration variable", &x)
// ok to continue
}
}
if key == nil {
check.errorf(x.pos(), "cannot range over %s", &x)
// if we don't have a declaration, we can still check the loop's body
if !decl {
check.stmt(inner, s.Body)
}
return
}
// check assignment to/declaration of iteration variables
// (irregular assignment, cannot easily map to existing assignment checks)
// lhs expressions and initialization value (rhs) types
lhs := [2]ast.Expr{s.Key, s.Value}
rhs := [2]Type{key, val}
if decl {
// short variable declaration; variable scope starts after the range clause
// (the for loop opens a new scope, so variables on the lhs never redeclare
// previously declared variables)
var vars []*Var
for i, lhs := range lhs {
if lhs == nil {
continue
}
// determine lhs variable
var obj *Var
if ident, _ := lhs.(*ast.Ident); ident != nil {
// declare new variable
name := ident.Name
obj = NewVar(ident.Pos(), check.pkg, name, nil)
check.recordDef(ident, obj)
// _ variables don't count as new variables
if name != "_" {
vars = append(vars, obj)
}
} else {
check.errorf(lhs.Pos(), "cannot declare %s", lhs)
obj = NewVar(lhs.Pos(), check.pkg, "_", nil) // dummy variable
}
// initialize lhs variable
x.mode = value
x.expr = lhs // we don't have a better rhs expression to use here
x.typ = rhs[i]
check.initVar(obj, &x, false)
}
// declare variables
if len(vars) > 0 {
for _, obj := range vars {
check.declare(check.scope, nil /* recordDef already called */, obj)
}
} else {
check.error(s.TokPos, "no new variables on left side of :=")
}
} else {
// ordinary assignment
for i, lhs := range lhs {
if lhs == nil {
continue
}
x.mode = value
x.expr = lhs // we don't have a better rhs expression to use here
x.typ = rhs[i]
check.assignVar(lhs, &x)
}
}
check.stmt(inner, s.Body)
default:
check.error(s.Pos(), "invalid statement")
}
}
// ConstValue = string | "false" | "true" | ["-"] (int ["'"] | FloatOrComplex) .
// FloatOrComplex = float ["i" | ("+"|"-") float "i"] .
func (p *parser) parseConstValue() (val exact.Value, typ types.Type) {
switch p.tok {
case scanner.String:
str := p.parseString()
val = exact.MakeString(str)
typ = types.Typ[types.UntypedString]
return
case scanner.Ident:
b := false
switch p.lit {
case "false":
case "true":
b = true
default:
p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
}
p.next()
val = exact.MakeBool(b)
typ = types.Typ[types.UntypedBool]
return
}
sign := ""
if p.tok == '-' {
p.next()
sign = "-"
}
switch p.tok {
case scanner.Int:
val = exact.MakeFromLiteral(sign+p.lit, token.INT)
if val == nil {
p.error("could not parse integer literal")
}
p.next()
if p.tok == '\'' {
p.next()
typ = types.Typ[types.UntypedRune]
} else {
typ = types.Typ[types.UntypedInt]
}
case scanner.Float:
re := sign + p.lit
p.next()
var im string
switch p.tok {
case '+':
p.next()
im = p.expect(scanner.Float)
case '-':
p.next()
im = "-" + p.expect(scanner.Float)
case scanner.Ident:
// re is in fact the imaginary component. Expect "i" below.
im = re
re = "0"
default:
val = exact.MakeFromLiteral(re, token.FLOAT)
if val == nil {
p.error("could not parse float literal")
}
typ = types.Typ[types.UntypedFloat]
return
}
p.expectKeyword("i")
reval := exact.MakeFromLiteral(re, token.FLOAT)
if reval == nil {
p.error("could not parse real component of complex literal")
}
imval := exact.MakeFromLiteral(im+"i", token.IMAG)
if imval == nil {
p.error("could not parse imag component of complex literal")
}
val = exact.BinaryOp(reval, token.ADD, imval)
typ = types.Typ[types.UntypedComplex]
default:
p.errorf("expected const value, got %s (%q)", scanner.TokenString(p.tok), p.lit)
}
return
}
// Error has a nil package in its qualified name since it is in no package
res := NewVar(token.NoPos, nil, "", Typ[String])
sig := &Signature{results: NewTuple(res)}
err := NewFunc(token.NoPos, nil, "Error", sig)
typ := &Named{underlying: NewInterface([]*Func{err}, nil).Complete()}
sig.recv = NewVar(token.NoPos, nil, "", typ)
def(NewTypeName(token.NoPos, nil, "error", typ))
}
var predeclaredConsts = [...]struct {
name string
kind BasicKind
val exact.Value
}{
{"true", UntypedBool, exact.MakeBool(true)},
{"false", UntypedBool, exact.MakeBool(false)},
{"iota", UntypedInt, exact.MakeInt64(0)},
}
func defPredeclaredConsts() {
for _, c := range predeclaredConsts {
def(NewConst(token.NoPos, nil, c.name, Typ[c.kind], c.val))
}
}
func defPredeclaredNil() {
def(&Nil{object{name: "nil", typ: Typ[UntypedNil]}})
}
// A builtinId is the id of a builtin function.
// ConstDecl = "const" ExportedName [ Type ] "=" Literal .
// Literal = bool_lit | int_lit | float_lit | complex_lit | rune_lit | string_lit .
// bool_lit = "true" | "false" .
// complex_lit = "(" float_lit "+" float_lit "i" ")" .
// rune_lit = "(" int_lit "+" int_lit ")" .
// string_lit = `"` { unicode_char } `"` .
//
func (p *parser) parseConstDecl() {
p.expectKeyword("const")
pkg, name := p.parseExportedName()
var typ0 types.Type
if p.tok != '=' {
typ0 = p.parseType()
}
p.expect('=')
var typ types.Type
var val exact.Value
switch p.tok {
case scanner.Ident:
// bool_lit
if p.lit != "true" && p.lit != "false" {
p.error("expected true or false")
}
typ = types.Typ[types.UntypedBool]
val = exact.MakeBool(p.lit == "true")
p.next()
case '-', scanner.Int:
// int_lit
typ, val = p.parseNumber()
case '(':
// complex_lit or rune_lit
p.next()
if p.tok == scanner.Char {
p.next()
p.expect('+')
typ = types.Typ[types.UntypedRune]
_, val = p.parseNumber()
p.expect(')')
break
}
_, re := p.parseNumber()
p.expect('+')
_, im := p.parseNumber()
p.expectKeyword("i")
p.expect(')')
typ = types.Typ[types.UntypedComplex]
val = exact.BinaryOp(re, token.ADD, exact.MakeImag(im))
case scanner.Char:
// rune_lit
typ = types.Typ[types.UntypedRune]
val = exact.MakeFromLiteral(p.lit, token.CHAR)
p.next()
case scanner.String:
// string_lit
typ = types.Typ[types.UntypedString]
val = exact.MakeFromLiteral(p.lit, token.STRING)
p.next()
default:
p.errorf("expected literal got %s", scanner.TokenString(p.tok))
}
if typ0 == nil {
typ0 = typ
}
pkg.Scope().Insert(types.NewConst(token.NoPos, pkg, name, typ0, val))
}