| // Copyright 2012 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. |
| |
| // This file implements typechecking of builtin function calls. |
| |
| package types |
| |
| import ( |
| "go/ast" |
| "go/constant" |
| "go/token" |
| ) |
| |
| // builtin type-checks a call to the built-in specified by id and |
| // reports whether 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(atPos(call.Ellipsis), |
| _InvalidDotDotDot, |
| "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(inNode(call, call.Rparen), _WrongArgCount, "%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, _InvalidAppend, "%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() { |
| if ok, _ := x.assignableTo(check, NewSlice(universeByte), nil); ok { |
| 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_ |
| if t.len >= 0 { |
| val = constant.MakeInt64(t.len) |
| } else { |
| val = constant.MakeUnknown() |
| } |
| } |
| |
| case *Slice, *Chan: |
| mode = value |
| |
| case *Map: |
| if id == _Len { |
| mode = value |
| } |
| } |
| |
| if mode == invalid && typ != Typ[Invalid] { |
| code := _InvalidCap |
| if id == _Len { |
| code = _InvalidLen |
| } |
| check.invalidArg(x, code, "%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, _InvalidClose, "%s is not a channel", x) |
| return |
| } |
| if c.dir == RecvOnly { |
| check.invalidArg(x, _InvalidClose, "%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 !check.identical(x.typ, y.typ) { |
| check.invalidArg(x, _InvalidComplex, "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, _InvalidComplex, "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, _InvalidCopy, "copy expects slice arguments; found %s and %s", x, &y) |
| return |
| } |
| |
| if !check.identical(dst, src) { |
| check.invalidArg(x, _InvalidCopy, "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, _InvalidDelete, "%s is not a map", x) |
| return |
| } |
| arg(x, 1) // k |
| if x.mode == invalid { |
| return |
| } |
| |
| if ok, code := x.assignableTo(check, m.key, nil); !ok { |
| check.invalidArg(x, code, "%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 always 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) { |
| code := _InvalidImag |
| if id == _Real { |
| code = _InvalidReal |
| } |
| check.invalidArg(x, code, "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, _InvalidMake, "cannot make %s; type must be slice, map, or channel", arg0) |
| return |
| } |
| if nargs < min || min+1 < nargs { |
| check.errorf(call, _WrongArgCount, "%v expects %d or %d arguments; found %d", call, min, min+1, nargs) |
| return |
| } |
| types := []Type{T} |
| var sizes []int64 // constant integer arguments, if any |
| for _, arg := range call.Args[1:] { |
| typ, size := check.index(arg, -1) // ok to continue with typ == Typ[Invalid] |
| types = append(types, typ) |
| if size >= 0 { |
| sizes = append(sizes, size) |
| } |
| } |
| if len(sizes) == 2 && sizes[0] > sizes[1] { |
| check.invalidArg(call.Args[1], _SwappedMakeArgs, "length and capacity swapped") |
| // safe to continue |
| } |
| x.mode = value |
| x.typ = T |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(x.typ, types...)) |
| } |
| |
| 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) |
| // record panic call if inside a function with result parameters |
| // (for use in Checker.isTerminating) |
| if check.sig != nil && check.sig.results.Len() > 0 { |
| // function has result parameters |
| p := check.isPanic |
| if p == nil { |
| // allocate lazily |
| p = make(map[*ast.CallExpr]bool) |
| check.isPanic = p |
| } |
| p[call] = true |
| } |
| |
| check.assignment(x, &emptyInterface, "argument to panic") |
| if x.mode == invalid { |
| return |
| } |
| |
| x.mode = novalue |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(nil, &emptyInterface)) |
| } |
| |
| 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 = &emptyInterface |
| 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, _BadOffsetofSyntax, "%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 := check.lookupFieldOrMethod(base, false, check.pkg, sel) |
| switch obj.(type) { |
| case nil: |
| check.invalidArg(x, _MissingFieldOrMethod, "%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, _InvalidOffsetof, "%s is a method value", arg0) |
| return |
| } |
| if indirect { |
| check.invalidArg(x, _InvalidOffsetof, "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, _Test, "%s is not a boolean constant", x) |
| return |
| } |
| if x.val.Kind() != constant.Bool { |
| check.errorf(x, _Test, "internal error: value of %s should be a boolean constant", x) |
| return |
| } |
| if !constant.BoolVal(x.val) { |
| check.errorf(call, _Test, "%v 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("%v: 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("%v: %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 |
| } |
| |
| // makeSig makes a signature for the given argument and result types. |
| // Default types are used for untyped arguments, and res may be nil. |
| func makeSig(res Type, args ...Type) *Signature { |
| list := make([]*Var, len(args)) |
| for i, param := range args { |
| list[i] = NewVar(token.NoPos, nil, "", Default(param)) |
| } |
| params := NewTuple(list...) |
| var result *Tuple |
| if res != nil { |
| assert(!isUntyped(res)) |
| result = NewTuple(NewVar(token.NoPos, nil, "", res)) |
| } |
| return &Signature{params: params, results: result} |
| } |
| |
| // implicitArrayDeref returns A if typ is of the form *A and A is an array; |
| // otherwise it returns typ. |
| // |
| func implicitArrayDeref(typ Type) Type { |
| if p, ok := typ.(*Pointer); ok { |
| if a, ok := p.base.Underlying().(*Array); ok { |
| return a |
| } |
| } |
| return typ |
| } |
| |
| // unparen returns e with any enclosing parentheses stripped. |
| func unparen(e ast.Expr) ast.Expr { |
| for { |
| p, ok := e.(*ast.ParenExpr) |
| if !ok { |
| return e |
| } |
| e = p.X |
| } |
| } |
