| // 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 types2 |
| |
| import ( |
| "cmd/compile/internal/syntax" |
| "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 *syntax.CallExpr, id builtinId) (_ bool) { |
| // append is the only built-in that permits the use of ... for the last argument |
| bin := predeclaredFuncs[id] |
| if call.HasDots && id != _Append { |
| //check.errorf(call.Ellipsis, invalidOp + "invalid use of ... with built-in %s", bin.name) |
| check.errorf(call, invalidOp+"invalid use of ... with built-in %s", bin.name) |
| check.use(call.ArgList...) |
| 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 exprList because exprList evaluates |
| // all arguments. |
| if id == _Len || id == _Cap { |
| defer func(b bool) { |
| check.hasCallOrRecv = b |
| }(check.hasCallOrRecv) |
| check.hasCallOrRecv = false |
| } |
| |
| // determine actual arguments |
| var arg func(*operand, int) // TODO(gri) remove use of arg getter in favor of using xlist directly |
| nargs := len(call.ArgList) |
| switch id { |
| default: |
| // make argument getter |
| xlist, _ := check.exprList(call.ArgList, false) |
| arg = func(x *operand, i int) { *x = *xlist[i] } |
| nargs = len(xlist) |
| // 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.errorf(call, invalidOp+"%s arguments for %v (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 := asSlice(S); s != nil { |
| T = s.elem |
| } else { |
| check.errorf(x, invalidArg+"%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.HasDots { |
| 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 |
| var xlist []*operand |
| // convert []operand to []*operand |
| for i := range alist { |
| xlist = append(xlist, &alist[i]) |
| } |
| for i := len(alist); i < nargs; i++ { |
| var x operand |
| arg(&x, i) |
| xlist = append(xlist, &x) |
| } |
| check.arguments(call, sig, nil, xlist) // discard result (we know the result type) |
| // 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 = arrayPtrDeref(under(x.typ)); 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 |
| } |
| |
| case *TypeParam: |
| if t.underIs(func(t Type) bool { |
| switch t := arrayPtrDeref(t).(type) { |
| case *Basic: |
| if isString(t) && id == _Len { |
| return true |
| } |
| case *Array, *Slice, *Chan: |
| return true |
| case *Map: |
| if id == _Len { |
| return true |
| } |
| } |
| return false |
| }) { |
| mode = value |
| } |
| } |
| |
| if mode == invalid && typ != Typ[Invalid] { |
| check.errorf(x, invalidArg+"%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) |
| if !underIs(x.typ, func(u Type) bool { |
| uch, _ := u.(*Chan) |
| if uch == nil { |
| check.errorf(x, invalidOp+"cannot close non-channel %s", x) |
| return false |
| } |
| if uch.dir == RecvOnly { |
| check.errorf(x, invalidOp+"cannot close receive-only channel %s", x) |
| return false |
| } |
| return true |
| }) { |
| return |
| } |
| x.mode = novalue |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(nil, x.typ)) |
| } |
| |
| 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.errorf(x, invalidOp+"%v (mismatched types %s and %s)", call, x.typ, y.typ) |
| return |
| } |
| |
| // the argument types must be of floating-point type |
| f := func(x Type) Type { |
| if t := asBasic(x); t != nil { |
| switch t.kind { |
| case Float32: |
| return Typ[Complex64] |
| case Float64: |
| return Typ[Complex128] |
| case UntypedFloat: |
| return Typ[UntypedComplex] |
| } |
| } |
| return nil |
| } |
| resTyp := check.applyTypeFunc(f, x.typ) |
| if resTyp == nil { |
| check.errorf(x, invalidArg+"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 |
| } |
| |
| 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 := asSlice(x.typ); t != nil { |
| dst = t.elem |
| } |
| |
| var y operand |
| arg(&y, 1) |
| if y.mode == invalid { |
| return |
| } |
| var src Type |
| switch t := under(y.typ).(type) { |
| case *Basic: |
| if isString(y.typ) { |
| src = universeByte |
| } |
| case *Slice: |
| src = t.elem |
| case *TypeParam: |
| check.error(x, "copy on generic operands not yet implemented") |
| } |
| |
| if dst == nil || src == nil { |
| check.errorf(x, invalidArg+"copy expects slice arguments; found %s and %s", x, &y) |
| return |
| } |
| |
| if !Identical(dst, src) { |
| check.errorf(x, invalidArg+"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(map_, key) |
| // map_ must be a map type or a type parameter describing map types. |
| // The key cannot be a type parameter for now. |
| map_ := x.typ |
| var key Type |
| if !underIs(map_, func(u Type) bool { |
| map_, _ := u.(*Map) |
| if map_ == nil { |
| check.errorf(x, invalidArg+"%s is not a map", x) |
| return false |
| } |
| if key != nil && !Identical(map_.key, key) { |
| check.errorf(x, invalidArg+"maps of %s must have identical key types", x) |
| return false |
| } |
| key = map_.key |
| return true |
| }) { |
| return |
| } |
| |
| arg(x, 1) // k |
| if x.mode == invalid { |
| return |
| } |
| |
| check.assignment(x, key, "argument to delete") |
| if x.mode == invalid { |
| return |
| } |
| |
| x.mode = novalue |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(nil, map_, 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 |
| f := func(x Type) Type { |
| if t := asBasic(x); t != nil { |
| switch t.kind { |
| case Complex64: |
| return Typ[Float32] |
| case Complex128: |
| return Typ[Float64] |
| case UntypedComplex: |
| return Typ[UntypedFloat] |
| } |
| } |
| return nil |
| } |
| resTyp := check.applyTypeFunc(f, x.typ) |
| if resTyp == nil { |
| check.errorf(x, invalidArg+"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 |
| } |
| |
| 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.ArgList[0] |
| T := check.varType(arg0) |
| if T == Typ[Invalid] { |
| return |
| } |
| |
| var min int // minimum number of arguments |
| switch optype(T).(type) { |
| case *Slice: |
| min = 2 |
| case *Map, *Chan: |
| min = 1 |
| case *top: |
| check.errorf(arg0, invalidArg+"cannot make %s; type parameter has no structural type", arg0) |
| return |
| default: |
| check.errorf(arg0, invalidArg+"cannot make %s; type must be slice, map, or channel", arg0) |
| return |
| } |
| if nargs < min || min+1 < nargs { |
| check.errorf(call, invalidOp+"%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.ArgList[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.error(call.ArgList[1], invalidArg+"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.varType(call.ArgList[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[*syntax.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 _Add: |
| // unsafe.Add(ptr unsafe.Pointer, len IntegerType) unsafe.Pointer |
| if !check.allowVersion(check.pkg, 1, 17) { |
| check.error(call.Fun, "unsafe.Add requires go1.17 or later") |
| return |
| } |
| |
| check.assignment(x, Typ[UnsafePointer], "argument to unsafe.Add") |
| if x.mode == invalid { |
| return |
| } |
| |
| var y operand |
| arg(&y, 1) |
| if !check.isValidIndex(&y, "length", true) { |
| return |
| } |
| |
| x.mode = value |
| x.typ = Typ[UnsafePointer] |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(x.typ, x.typ, y.typ)) |
| } |
| |
| case _Alignof: |
| // unsafe.Alignof(x T) uintptr |
| check.assignment(x, nil, "argument to unsafe.Alignof") |
| if x.mode == invalid { |
| return |
| } |
| |
| if hasVarSize(x.typ) { |
| x.mode = value |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], x.typ)) |
| } |
| } else { |
| x.mode = constant_ |
| x.val = constant.MakeInt64(check.conf.alignof(x.typ)) |
| // result is constant - no need to record signature |
| } |
| x.typ = Typ[Uintptr] |
| |
| case _Offsetof: |
| // unsafe.Offsetof(x T) uintptr, where x must be a selector |
| // (no argument evaluated yet) |
| arg0 := call.ArgList[0] |
| selx, _ := unparen(arg0).(*syntax.SelectorExpr) |
| if selx == nil { |
| check.errorf(arg0, invalidArg+"%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.Value |
| obj, index, indirect := LookupFieldOrMethod(base, false, check.pkg, sel) |
| switch obj.(type) { |
| case nil: |
| check.errorf(x, invalidArg+"%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.errorf(arg0, invalidArg+"%s is a method value", arg0) |
| return |
| } |
| if indirect { |
| check.errorf(x, invalidArg+"field %s is embedded via a pointer in %s", sel, base) |
| return |
| } |
| |
| // TODO(gri) Should we pass x.typ instead of base (and have indirect report if derefStructPtr indirected)? |
| check.recordSelection(selx, FieldVal, base, obj, index, false) |
| |
| // record the selector expression (was bug - issue #47895) |
| { |
| mode := value |
| if x.mode == variable || indirect { |
| mode = variable |
| } |
| check.record(&operand{mode, selx, obj.Type(), nil, 0}) |
| } |
| |
| // The field offset is considered a variable even if the field is declared before |
| // the part of the struct which is variable-sized. This makes both the rules |
| // simpler and also permits (or at least doesn't prevent) a compiler from re- |
| // arranging struct fields if it wanted to. |
| if hasVarSize(base) { |
| x.mode = value |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], obj.Type())) |
| } |
| } else { |
| x.mode = constant_ |
| x.val = constant.MakeInt64(check.conf.offsetof(base, index)) |
| // result is constant - no need to record signature |
| } |
| x.typ = Typ[Uintptr] |
| |
| case _Sizeof: |
| // unsafe.Sizeof(x T) uintptr |
| check.assignment(x, nil, "argument to unsafe.Sizeof") |
| if x.mode == invalid { |
| return |
| } |
| |
| if hasVarSize(x.typ) { |
| x.mode = value |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(Typ[Uintptr], x.typ)) |
| } |
| } else { |
| x.mode = constant_ |
| x.val = constant.MakeInt64(check.conf.sizeof(x.typ)) |
| // result is constant - no need to record signature |
| } |
| x.typ = Typ[Uintptr] |
| |
| case _Slice: |
| // unsafe.Slice(ptr *T, len IntegerType) []T |
| if !check.allowVersion(check.pkg, 1, 17) { |
| check.error(call.Fun, "unsafe.Slice requires go1.17 or later") |
| return |
| } |
| |
| typ := asPointer(x.typ) |
| if typ == nil { |
| check.errorf(x, invalidArg+"%s is not a pointer", x) |
| return |
| } |
| |
| var y operand |
| arg(&y, 1) |
| if !check.isValidIndex(&y, "length", false) { |
| return |
| } |
| |
| x.mode = value |
| x.typ = NewSlice(typ.base) |
| if check.Types != nil { |
| check.recordBuiltinType(call.Fun, makeSig(x.typ, typ, y.typ)) |
| } |
| |
| 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.errorf(x, invalidArg+"%s is not a boolean constant", x) |
| return |
| } |
| if x.val.Kind() != constant.Bool { |
| check.errorf(x, "internal error: value of %s should be a boolean constant", x) |
| return |
| } |
| if !constant.BoolVal(x.val) { |
| check.errorf(call, "%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", posFor(call)) |
| x.mode = novalue |
| break |
| } |
| var t operand |
| x1 := x |
| for _, arg := range call.ArgList { |
| check.rawExpr(x1, arg, nil) // permit trace for types, e.g.: new(trace(T)) |
| check.dump("%v: %s", posFor(x1), 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 |
| } |
| |
| // hasVarSize reports if the size of type t is variable due to type parameters. |
| func hasVarSize(t Type) bool { |
| switch t := under(t).(type) { |
| case *Array: |
| return hasVarSize(t.elem) |
| case *Struct: |
| for _, f := range t.fields { |
| if hasVarSize(f.typ) { |
| return true |
| } |
| } |
| case *TypeParam: |
| return true |
| case *Named, *Union, *top: |
| unreachable() |
| } |
| return false |
| } |
| |
| // applyTypeFunc applies f to x. If x is a type parameter, |
| // the result is a type parameter constrained by an new |
| // interface bound. The type bounds for that interface |
| // are computed by applying f to each of the type bounds |
| // of x. If any of these applications of f return nil, |
| // applyTypeFunc returns nil. |
| // If x is not a type parameter, the result is f(x). |
| func (check *Checker) applyTypeFunc(f func(Type) Type, x Type) Type { |
| if tp := asTypeParam(x); tp != nil { |
| // Test if t satisfies the requirements for the argument |
| // type and collect possible result types at the same time. |
| var terms []*Term |
| if !tp.iface().typeSet().is(func(t *term) bool { |
| if r := f(t.typ); r != nil { |
| terms = append(terms, NewTerm(t.tilde, r)) |
| return true |
| } |
| return false |
| }) { |
| return nil |
| } |
| |
| // TODO(gri) Would it be ok to return just the one type |
| // if len(rtypes) == 1? What about top-level |
| // uses of real() where the result is used to |
| // define type and initialize a variable? |
| |
| // Construct a suitable new type parameter for the sum type. The |
| // type param is placed in the current package so export/import |
| // works as expected. |
| tpar := NewTypeName(nopos, check.pkg, "<type parameter>", nil) |
| ptyp := check.NewTypeParam(tpar, NewInterfaceType(nil, []Type{NewUnion(terms)})) // assigns type to tpar as a side-effect |
| ptyp.index = tp.index |
| |
| return ptyp |
| } |
| |
| return f(x) |
| } |
| |
| // 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(nopos, nil, "", Default(param)) |
| } |
| params := NewTuple(list...) |
| var result *Tuple |
| if res != nil { |
| assert(!isUntyped(res)) |
| result = NewTuple(NewVar(nopos, nil, "", res)) |
| } |
| return &Signature{params: params, results: result} |
| } |
| |
| // arrayPtrDeref returns A if typ is of the form *A and A is an array; |
| // otherwise it returns typ. |
| func arrayPtrDeref(typ Type) Type { |
| if p, ok := typ.(*Pointer); ok { |
| if a := asArray(p.base); a != nil { |
| return a |
| } |
| } |
| return typ |
| } |
| |
| // unparen returns e with any enclosing parentheses stripped. |
| func unparen(e syntax.Expr) syntax.Expr { |
| for { |
| p, ok := e.(*syntax.ParenExpr) |
| if !ok { |
| return e |
| } |
| e = p.X |
| } |
| } |