// collectObjects collects all file and package objects and inserts them
// into their respective scopes. It also performs imports and associates
// methods with receiver base type names.
func (check *Checker) collectObjects() {
pkg := check.pkg
// pkgImports is the set of packages already imported by any package file seen
// so far. Used to avoid duplicate entries in pkg.imports. Allocate and populate
// it (pkg.imports may not be empty if we are checking test files incrementally).
var pkgImports = make(map[*Package]bool)
for _, imp := range pkg.imports {
pkgImports[imp] = true
}
// srcDir is the directory used by the Importer to look up packages.
// The typechecker itself doesn't need this information so it is not
// explicitly provided. Instead, we extract it from position info of
// the source files as needed.
// This is the only place where the type-checker (just the importer)
// needs to know the actual source location of a file.
// TODO(gri) can we come up with a better API instead?
var srcDir string
if len(check.files) > 0 {
// FileName may be "" (typically for tests) in which case
// we get "." as the srcDir which is what we would want.
srcDir = dir(check.fset.Position(check.files[0].Name.Pos()).Filename)
}
for fileNo, file := range check.files {
// The package identifier denotes the current package,
// but there is no corresponding package object.
check.recordDef(file.Name, nil)
// Use the actual source file extent rather than *ast.File extent since the
// latter doesn't include comments which appear at the start or end of the file.
// Be conservative and use the *ast.File extent if we don't have a *token.File.
pos, end := file.Pos(), file.End()
if f := check.fset.File(file.Pos()); f != nil {
pos, end = token.Pos(f.Base()), token.Pos(f.Base()+f.Size())
}
fileScope := NewScope(check.pkg.scope, pos, end, check.filename(fileNo))
check.recordScope(file, fileScope)
for _, decl := range file.Decls {
switch d := decl.(type) {
case *ast.BadDecl:
// ignore
case *ast.GenDecl:
var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
for iota, spec := range d.Specs {
switch s := spec.(type) {
case *ast.ImportSpec:
// import package
var imp *Package
path, err := validatedImportPath(s.Path.Value)
if err != nil {
check.errorf(s.Path.Pos(), "invalid import path (%s)", err)
continue
}
if path == "C" && check.conf.FakeImportC {
// TODO(gri) shouldn't create a new one each time
imp = NewPackage("C", "C")
imp.fake = true
} else {
// ordinary import
if importer := check.conf.Importer; importer == nil {
err = fmt.Errorf("Config.Importer not installed")
} else if importerFrom, ok := importer.(ImporterFrom); ok {
imp, err = importerFrom.ImportFrom(path, srcDir, 0)
if imp == nil && err == nil {
err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, pkg.path)
}
} else {
imp, err = importer.Import(path)
if imp == nil && err == nil {
err = fmt.Errorf("Config.Importer.Import(%s) returned nil but no error", path)
}
}
if err != nil {
check.errorf(s.Path.Pos(), "could not import %s (%s)", path, err)
continue
}
}
// add package to list of explicit imports
// (this functionality is provided as a convenience
// for clients; it is not needed for type-checking)
if !pkgImports[imp] {
pkgImports[imp] = true
if imp != Unsafe {
pkg.imports = append(pkg.imports, imp)
}
}
// local name overrides imported package name
name := imp.name
if s.Name != nil {
name = s.Name.Name
if path == "C" {
// match cmd/compile (not prescribed by spec)
check.errorf(s.Name.Pos(), `cannot rename import "C"`)
continue
}
if name == "init" {
check.errorf(s.Name.Pos(), "cannot declare init - must be func")
continue
}
}
obj := NewPkgName(s.Pos(), pkg, name, imp)
if s.Name != nil {
// in a dot-import, the dot represents the package
check.recordDef(s.Name, obj)
} else {
check.recordImplicit(s, obj)
}
if path == "C" {
// match cmd/compile (not prescribed by spec)
obj.used = true
}
// add import to file scope
if name == "." {
// merge imported scope with file scope
for _, obj := range imp.scope.elems {
// A package scope may contain non-exported objects,
// do not import them!
if obj.Exported() {
// TODO(gri) When we import a package, we create
// a new local package object. We should do the
// same for each dot-imported object. That way
// they can have correct position information.
// (We must not modify their existing position
// information because the same package - found
// via Config.Packages - may be dot-imported in
// another package!)
check.declare(fileScope, nil, obj, token.NoPos)
check.recordImplicit(s, obj)
}
}
// add position to set of dot-import positions for this file
// (this is only needed for "imported but not used" errors)
check.addUnusedDotImport(fileScope, imp, s.Pos())
} else {
// declare imported package object in file scope
check.declare(fileScope, nil, obj, token.NoPos)
}
case *ast.ValueSpec:
switch d.Tok {
case token.CONST:
// determine which initialization expressions to use
switch {
case s.Type != nil || len(s.Values.List) > 0:
last = s
case last == nil:
last = new(ast.ValueSpec) // make sure last exists
}
// declare all constants
for i, name := range s.Names.List {
obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(iota)))
var init ast.Expr
if last.Values != nil && i < len(last.Values.List) {
init = last.Values.List[i]
}
d := &declInfo{file: fileScope, typ: last.Type, init: init}
check.declarePkgObj(name, obj, d)
}
check.arityMatch(s, last)
case token.VAR:
lhsLen := len(s.Names.List)
if s.Names.EntangledPos > 0 {
lhsLen--
}
lhs := make([]*Var, lhsLen)
// If there's exactly one rhs initializer, use
// the same declInfo d1 for all lhs variables
// so that each lhs variable depends on the same
// rhs initializer (n:1 var declaration).
var d1 *declInfo
if len(s.Values.List) == 1 {
// The lhs elements are only set up after the for loop below,
// but that's ok because declareVar only collects the declInfo
// for a later phase.
d1 = &declInfo{file: fileScope, lhs: lhs, typ: s.Type, init: s.Values.List[0]}
}
// declare all variables
for i, name := range s.Names.List {
obj := NewVar(name.Pos(), pkg, name.Name, nil)
d := d1
if d == nil {
// individual assignments
var init ast.Expr
if i < len(s.Values.List) {
init = s.Values.List[i]
}
d = &declInfo{file: fileScope, typ: s.Type, init: init}
}
if s.Names.EntangledPos > 0 && i == s.Names.EntangledPos-1 {
d.entangledLhs = obj
} else {
lhs[i] = obj
}
check.declarePkgObj(name, obj, d)
}
check.arityMatch(s, nil)
default:
check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
}
case *ast.TypeSpec:
obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
check.declarePkgObj(s.Name, obj, &declInfo{file: fileScope, typ: s.Type})
default:
check.invalidAST(s.Pos(), "unknown ast.Spec node %T", s)
}
}
case *ast.FuncDecl:
name := d.Name.Name
obj := NewFunc(d.Name.Pos(), pkg, name, nil)
if d.Recv == nil {
// regular function
if name == "init" {
// don't declare init functions in the package scope - they are invisible
obj.parent = pkg.scope
check.recordDef(d.Name, obj)
// init functions must have a body
if d.Body == nil {
check.softErrorf(obj.pos, "missing function body")
}
} else {
check.declare(pkg.scope, d.Name, obj, token.NoPos)
}
} else {
// method
check.recordDef(d.Name, obj)
// Associate method with receiver base type name, if possible.
// Ignore methods that have an invalid receiver, or a blank _
// receiver name. They will be type-checked later, with regular
// functions.
if list := d.Recv.List; len(list) > 0 {
typ := list[0].Type
if opt, _ := typ.(*ast.OptionalType); opt != nil {
typ = opt.Elt
}
if ptr, _ := typ.(*ast.StarExpr); ptr != nil {
typ = ptr.X
}
if base, _ := typ.(*ast.Ident); base != nil && base.Name != "_" {
check.assocMethod(base.Name, obj)
}
}
}
info := &declInfo{file: fileScope, fdecl: d}
check.objMap[obj] = info
obj.setOrder(uint32(len(check.objMap)))
default:
check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
}
}
}
// verify that objects in package and file scopes have different names
for _, scope := range check.pkg.scope.children /* file scopes */ {
for _, obj := range scope.elems {
if alt := pkg.scope.Lookup(obj.Name()); alt != nil {
if pkg, ok := obj.(*PkgName); ok {
check.errorf(alt.Pos(), "%s already declared through import of %s", alt.Name(), pkg.Imported())
check.reportAltDecl(pkg)
} else {
check.errorf(alt.Pos(), "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
// TODO(gri) dot-imported objects don't have a position; reportAltDecl won't print anything
check.reportAltDecl(obj)
}
}
}
}
}
func (check *Checker) declStmt(decl ast.Decl) {
pkg := check.pkg
switch d := decl.(type) {
case *ast.BadDecl:
// ignore
case *ast.GenDecl:
var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
for iota, spec := range d.Specs {
switch s := spec.(type) {
case *ast.ValueSpec:
switch d.Tok {
case token.CONST:
// determine which init exprs to use
switch {
case s.Type != nil || len(s.Values.List) > 0:
last = s
case last == nil:
last = new(ast.ValueSpec) // make sure last exists
}
// declare all constants
lhs := make([]*Const, len(s.Names.List))
for i, name := range s.Names.List {
obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(iota)))
lhs[i] = obj
var init ast.Expr
if last.Values != nil && i < len(last.Values.List) {
init = last.Values.List[i]
}
check.constDecl(obj, last.Type, init)
}
check.arityMatch(s, last)
// spec: "The scope of a constant or variable identifier declared
// inside a function begins at the end of the ConstSpec or VarSpec
// (ShortVarDecl for short variable declarations) and ends at the
// end of the innermost containing block."
scopePos := s.End()
for i, name := range s.Names.List {
check.declare(check.scope, name, lhs[i], scopePos)
}
case token.VAR:
lhs0 := make([]*Var, 0, len(s.Names.List))
var entangledLhs *Var
for i, name := range s.Names.List {
v := NewVar(name.Pos(), pkg, name.Name, nil)
if s.Names.EntangledPos > 0 && i == s.Names.EntangledPos-1 {
entangledLhs = v
} else {
lhs0 = append(lhs0, v)
}
}
// initialize all variables
for i, obj := range lhs0 {
var lhs []*Var
var init ast.Expr
switch len(s.Values.List) {
case len(s.Names.List):
// lhs and rhs match
init = s.Values.List[i]
case 1:
// rhs is expected to be a multi-valued expression
lhs = lhs0
init = s.Values.List[0]
default:
if i < len(s.Values.List) {
init = s.Values.List[i]
}
}
check.varDecl(obj, lhs, entangledLhs, s.Type, init)
if len(s.Values.List) == 1 {
// If we have a single lhs variable we are done either way.
// If we have a single rhs expression, it must be a multi-
// valued expression, in which case handling the first lhs
// variable will cause all lhs variables to have a type
// assigned, and we are done as well.
if debug {
for _, obj := range lhs0 {
assert(obj.typ != nil)
}
}
break
}
}
check.arityMatch(s, nil)
// declare all variables
// (only at this point are the variable scopes (parents) set)
scopePos := s.End() // see constant declarations
for i, name := range s.Names.List {
var v *Var
if s.Names.EntangledPos > 0 && i == s.Names.EntangledPos-1 {
v = entangledLhs
} else {
v = lhs0[i]
}
// see constant declarations
check.declare(check.scope, name, v, scopePos)
}
default:
check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
}
case *ast.TypeSpec:
obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
// spec: "The scope of a type identifier declared inside a function
// begins at the identifier in the TypeSpec and ends at the end of
// the innermost containing block."
scopePos := s.Name.Pos()
check.declare(check.scope, s.Name, obj, scopePos)
check.typeDecl(obj, s.Type, nil, nil)
default:
check.invalidAST(s.Pos(), "const, type, or var declaration expected")
}
}
default:
check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
}
}
// builtin type-checks a call to the built-in specified by id and
// returns true if the call is valid, with *x holding the result;
// but x.expr is not set. If the call is invalid, the result is
// false, and *x is undefined.
//
func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ bool) {
// append is the only built-in that permits the use of ... for the last argument
bin := predeclaredFuncs[id]
if call.Ellipsis.IsValid() && id != _Append {
check.invalidOp(call.Ellipsis, "invalid use of ... with built-in %s", bin.name)
check.use(call.Args...)
return
}
// For len(x) and cap(x) we need to know if x contains any function calls or
// receive operations. Save/restore current setting and set hasCallOrRecv to
// false for the evaluation of x so that we can check it afterwards.
// Note: We must do this _before_ calling unpack because unpack evaluates the
// first argument before we even call arg(x, 0)!
if id == _Len || id == _Cap {
defer func(b bool) {
check.hasCallOrRecv = b
}(check.hasCallOrRecv)
check.hasCallOrRecv = false
}
// determine actual arguments
var arg getter
nargs := len(call.Args)
switch id {
default:
// make argument getter
arg, nargs, _ = unpack(func(x *operand, i int) { check.multiExpr(x, call.Args[i]) }, nargs, false)
if arg == nil {
return
}
// evaluate first argument, if present
if nargs > 0 {
arg(x, 0)
if x.mode == invalid {
return
}
}
case _Make, _New, _Offsetof, _Trace:
// arguments require special handling
}
// check argument count
{
msg := ""
if nargs < bin.nargs {
msg = "not enough"
} else if !bin.variadic && nargs > bin.nargs {
msg = "too many"
}
if msg != "" {
check.invalidOp(call.Rparen, "%s arguments for %s (expected %d, found %d)", msg, call, bin.nargs, nargs)
return
}
}
switch id {
case _Append:
// append(s S, x ...T) S, where T is the element type of S
// spec: "The variadic function append appends zero or more values x to s of type
// S, which must be a slice type, and returns the resulting slice, also of type S.
// The values x are passed to a parameter of type ...T where T is the element type
// of S and the respective parameter passing rules apply."
S := x.typ
var T Type
if s, _ := S.Underlying().(*Slice); s != nil {
T = s.elem
} else {
check.invalidArg(x.pos(), "%s is not a slice", x)
return
}
// remember arguments that have been evaluated already
alist := []operand{*x}
// spec: "As a special case, append also accepts a first argument assignable
// to type []byte with a second argument of string type followed by ... .
// This form appends the bytes of the string.
if nargs == 2 && call.Ellipsis.IsValid() && x.assignableTo(check.conf, NewSlice(universeByte), nil) {
arg(x, 1)
if x.mode == invalid {
return
}
if isString(x.typ) {
if check.Types != nil {
sig := makeSig(S, S, x.typ)
sig.variadic = true
check.recordBuiltinType(call.Fun, sig)
}
x.mode = value
x.typ = S
break
}
alist = append(alist, *x)
// fallthrough
}
// check general case by creating custom signature
sig := makeSig(S, S, NewSlice(T)) // []T required for variadic signature
sig.variadic = true
check.arguments(x, call, sig, func(x *operand, i int) {
// only evaluate arguments that have not been evaluated before
if i < len(alist) {
*x = alist[i]
return
}
arg(x, i)
}, nargs)
// ok to continue even if check.arguments reported errors
x.mode = value
x.typ = S
if check.Types != nil {
check.recordBuiltinType(call.Fun, sig)
}
case _Cap, _Len:
// cap(x)
// len(x)
mode := invalid
var typ Type
var val constant.Value
switch typ = implicitArrayDeref(x.typ.Underlying()); t := typ.(type) {
case *Basic:
if isString(t) && id == _Len {
if x.mode == constant_ {
mode = constant_
val = constant.MakeInt64(int64(len(constant.StringVal(x.val))))
} else {
mode = value
}
}
case *Array:
mode = value
// spec: "The expressions len(s) and cap(s) are constants
// if the type of s is an array or pointer to an array and
// the expression s does not contain channel receives or
// function calls; in this case s is not evaluated."
if !check.hasCallOrRecv {
mode = constant_
val = constant.MakeInt64(t.len)
}
case *Slice, *Chan:
mode = value
case *Map:
if id == _Len {
mode = value
}
}
if mode == invalid {
check.invalidArg(x.pos(), "%s for %s", x, bin.name)
return
}
x.mode = mode
x.typ = Typ[Int]
x.val = val
if check.Types != nil && mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(x.typ, typ))
}
case _Close:
// close(c)
c, _ := x.typ.Underlying().(*Chan)
if c == nil {
check.invalidArg(x.pos(), "%s is not a channel", x)
return
}
if c.dir == RecvOnly {
check.invalidArg(x.pos(), "%s must not be a receive-only channel", x)
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, c))
}
case _Complex:
// complex(x, y floatT) complexT
var y operand
arg(&y, 1)
if y.mode == invalid {
return
}
// convert or check untyped arguments
d := 0
if isUntyped(x.typ) {
d |= 1
}
if isUntyped(y.typ) {
d |= 2
}
switch d {
case 0:
// x and y are typed => nothing to do
case 1:
// only x is untyped => convert to type of y
check.convertUntyped(x, y.typ)
case 2:
// only y is untyped => convert to type of x
check.convertUntyped(&y, x.typ)
case 3:
// x and y are untyped =>
// 1) if both are constants, convert them to untyped
// floating-point numbers if possible,
// 2) if one of them is not constant (possible because
// it contains a shift that is yet untyped), convert
// both of them to float64 since they must have the
// same type to succeed (this will result in an error
// because shifts of floats are not permitted)
if x.mode == constant_ && y.mode == constant_ {
toFloat := func(x *operand) {
if isNumeric(x.typ) && constant.Sign(constant.Imag(x.val)) == 0 {
x.typ = Typ[UntypedFloat]
}
}
toFloat(x)
toFloat(&y)
} else {
check.convertUntyped(x, Typ[Float64])
check.convertUntyped(&y, Typ[Float64])
// x and y should be invalid now, but be conservative
// and check below
}
}
if x.mode == invalid || y.mode == invalid {
return
}
// both argument types must be identical
if !Identical(x.typ, y.typ) {
check.invalidArg(x.pos(), "mismatched types %s and %s", x.typ, y.typ)
return
}
// the argument types must be of floating-point type
if !isFloat(x.typ) {
check.invalidArg(x.pos(), "arguments have type %s, expected floating-point", x.typ)
return
}
// if both arguments are constants, the result is a constant
if x.mode == constant_ && y.mode == constant_ {
x.val = constant.BinaryOp(constant.ToFloat(x.val), token.ADD, constant.MakeImag(constant.ToFloat(y.val)))
} else {
x.mode = value
}
// determine result type
var res BasicKind
switch x.typ.Underlying().(*Basic).kind {
case Float32:
res = Complex64
case Float64:
res = Complex128
case UntypedFloat:
res = UntypedComplex
default:
unreachable()
}
resTyp := Typ[res]
if check.Types != nil && x.mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(resTyp, x.typ, x.typ))
}
x.typ = resTyp
case _Copy:
// copy(x, y []T) int
var dst Type
if t, _ := x.typ.Underlying().(*Slice); t != nil {
dst = t.elem
}
var y operand
arg(&y, 1)
if y.mode == invalid {
return
}
var src Type
switch t := y.typ.Underlying().(type) {
case *Basic:
if isString(y.typ) {
src = universeByte
}
case *Slice:
src = t.elem
}
if dst == nil || src == nil {
check.invalidArg(x.pos(), "copy expects slice arguments; found %s and %s", x, &y)
return
}
if !Identical(dst, src) {
check.invalidArg(x.pos(), "arguments to copy %s and %s have different element types %s and %s", x, &y, dst, src)
return
}
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(Typ[Int], x.typ, y.typ))
}
x.mode = value
x.typ = Typ[Int]
case _Delete:
// delete(m, k)
m, _ := x.typ.Underlying().(*Map)
if m == nil {
check.invalidArg(x.pos(), "%s is not a map", x)
return
}
arg(x, 1) // k
if x.mode == invalid {
return
}
if !x.assignableTo(check.conf, m.key, nil) {
check.invalidArg(x.pos(), "%s is not assignable to %s", x, m.key)
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, m, m.key))
}
case _Imag, _Real:
// imag(complexT) floatT
// real(complexT) floatT
// convert or check untyped argument
if isUntyped(x.typ) {
if x.mode == constant_ {
// an untyped constant number can alway be considered
// as a complex constant
if isNumeric(x.typ) {
x.typ = Typ[UntypedComplex]
}
} else {
// an untyped non-constant argument may appear if
// it contains a (yet untyped non-constant) shift
// expression: convert it to complex128 which will
// result in an error (shift of complex value)
check.convertUntyped(x, Typ[Complex128])
// x should be invalid now, but be conservative and check
if x.mode == invalid {
return
}
}
}
// the argument must be of complex type
if !isComplex(x.typ) {
check.invalidArg(x.pos(), "argument has type %s, expected complex type", x.typ)
return
}
// if the argument is a constant, the result is a constant
if x.mode == constant_ {
if id == _Real {
x.val = constant.Real(x.val)
} else {
x.val = constant.Imag(x.val)
}
} else {
x.mode = value
}
// determine result type
var res BasicKind
switch x.typ.Underlying().(*Basic).kind {
case Complex64:
res = Float32
case Complex128:
res = Float64
case UntypedComplex:
res = UntypedFloat
default:
unreachable()
}
resTyp := Typ[res]
if check.Types != nil && x.mode != constant_ {
check.recordBuiltinType(call.Fun, makeSig(resTyp, x.typ))
}
x.typ = resTyp
case _Make:
// make(T, n)
// make(T, n, m)
// (no argument evaluated yet)
arg0 := call.Args[0]
T := check.typ(arg0)
if T == Typ[Invalid] {
return
}
var min int // minimum number of arguments
switch T.Underlying().(type) {
case *Slice:
min = 2
case *Map, *Chan:
min = 1
default:
check.invalidArg(arg0.Pos(), "cannot make %s; type must be slice, map, or channel", arg0)
return
}
if nargs < min || min+1 < nargs {
check.errorf(call.Pos(), "%s expects %d or %d arguments; found %d", call, min, min+1, nargs)
return
}
var sizes []int64 // constant integer arguments, if any
for _, arg := range call.Args[1:] {
if s, ok := check.index(arg, -1); ok && s >= 0 {
sizes = append(sizes, s)
}
}
if len(sizes) == 2 && sizes[0] > sizes[1] {
check.invalidArg(call.Args[1].Pos(), "length and capacity swapped")
// safe to continue
}
x.mode = value
x.typ = T
if check.Types != nil {
params := [...]Type{T, Typ[Int], Typ[Int]}
check.recordBuiltinType(call.Fun, makeSig(x.typ, params[:1+len(sizes)]...))
}
case _New:
// new(T)
// (no argument evaluated yet)
T := check.typ(call.Args[0])
if T == Typ[Invalid] {
return
}
x.mode = value
x.typ = &Pointer{base: T}
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ, T))
}
case _Panic:
// panic(x)
T := new(Interface)
check.assignment(x, T, "argument to panic")
if x.mode == invalid {
return
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, T))
}
case _Print, _Println:
// print(x, y, ...)
// println(x, y, ...)
var params []Type
if nargs > 0 {
params = make([]Type, nargs)
for i := 0; i < nargs; i++ {
if i > 0 {
arg(x, i) // first argument already evaluated
}
check.assignment(x, nil, "argument to "+predeclaredFuncs[id].name)
if x.mode == invalid {
// TODO(gri) "use" all arguments?
return
}
params[i] = x.typ
}
}
x.mode = novalue
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(nil, params...))
}
case _Recover:
// recover() interface{}
x.mode = value
x.typ = NewOptional(new(Interface))
if check.Types != nil {
check.recordBuiltinType(call.Fun, makeSig(x.typ))
}
case _Alignof:
// unsafe.Alignof(x T) uintptr
check.assignment(x, nil, "argument to unsafe.Alignof")
if x.mode == invalid {
return
}
x.mode = constant_
x.val = constant.MakeInt64(check.conf.alignof(x.typ))
x.typ = Typ[Uintptr]
// result is constant - no need to record signature
case _Offsetof:
// unsafe.Offsetof(x T) uintptr, where x must be a selector
// (no argument evaluated yet)
arg0 := call.Args[0]
selx, _ := unparen(arg0).(*ast.SelectorExpr)
if selx == nil {
check.invalidArg(arg0.Pos(), "%s is not a selector expression", arg0)
check.use(arg0)
return
}
check.expr(x, selx.X)
if x.mode == invalid {
return
}
base := derefStructPtr(x.typ)
sel := selx.Sel.Name
obj, index, indirect := LookupFieldOrMethod(base, false, check.pkg, sel)
switch obj.(type) {
case nil:
check.invalidArg(x.pos(), "%s has no single field %s", base, sel)
return
case *Func:
// TODO(gri) Using derefStructPtr may result in methods being found
// that don't actually exist. An error either way, but the error
// message is confusing. See: https://play.golang.org/p/al75v23kUy ,
// but go/types reports: "invalid argument: x.m is a method value".
check.invalidArg(arg0.Pos(), "%s is a method value", arg0)
return
}
if indirect {
check.invalidArg(x.pos(), "field %s is embedded via a pointer in %s", sel, base)
return
}
// TODO(gri) Should we pass x.typ instead of base (and indirect report if derefStructPtr indirected)?
check.recordSelection(selx, FieldVal, base, obj, index, false)
offs := check.conf.offsetof(base, index)
x.mode = constant_
x.val = constant.MakeInt64(offs)
x.typ = Typ[Uintptr]
// result is constant - no need to record signature
case _Sizeof:
// unsafe.Sizeof(x T) uintptr
check.assignment(x, nil, "argument to unsafe.Sizeof")
if x.mode == invalid {
return
}
x.mode = constant_
x.val = constant.MakeInt64(check.conf.sizeof(x.typ))
x.typ = Typ[Uintptr]
// result is constant - no need to record signature
case _Assert:
// assert(pred) causes a typechecker error if pred is false.
// The result of assert is the value of pred if there is no error.
// Note: assert is only available in self-test mode.
if x.mode != constant_ || !isBoolean(x.typ) {
check.invalidArg(x.pos(), "%s is not a boolean constant", x)
return
}
if x.val.Kind() != constant.Bool {
check.errorf(x.pos(), "internal error: value of %s should be a boolean constant", x)
return
}
if !constant.BoolVal(x.val) {
check.errorf(call.Pos(), "%s failed", call)
// compile-time assertion failure - safe to continue
}
// result is constant - no need to record signature
case _Trace:
// trace(x, y, z, ...) dumps the positions, expressions, and
// values of its arguments. The result of trace is the value
// of the first argument.
// Note: trace is only available in self-test mode.
// (no argument evaluated yet)
if nargs == 0 {
check.dump("%s: trace() without arguments", call.Pos())
x.mode = novalue
break
}
var t operand
x1 := x
for _, arg := range call.Args {
check.rawExpr(x1, arg, nil) // permit trace for types, e.g.: new(trace(T))
check.dump("%s: %s", x1.pos(), x1)
x1 = &t // use incoming x only for first argument
}
// trace is only available in test mode - no need to record signature
default:
unreachable()
}
return true
}
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 constant.Value
}{
{"true", UntypedBool, constant.MakeBool(true)},
{"false", UntypedBool, constant.MakeBool(false)},
{"iota", UntypedInt, constant.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.
type builtinId int