| // 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 defines operands and associated operations. |
| |
| package types |
| |
| import ( |
| "bytes" |
| "go/ast" |
| "go/constant" |
| "go/token" |
| ) |
| |
| // An operandMode specifies the (addressing) mode of an operand. |
| type operandMode byte |
| |
| const ( |
| invalid operandMode = iota // operand is invalid |
| novalue // operand represents no value (result of a function call w/o result) |
| builtin // operand is a built-in function |
| typexpr // operand is a type |
| constant_ // operand is a constant; the operand's typ is a Basic type |
| variable // operand is an addressable variable |
| mapindex // operand is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment) |
| value // operand is a computed value |
| commaok // like value, but operand may be used in a comma,ok expression |
| ) |
| |
| var operandModeString = [...]string{ |
| invalid: "invalid operand", |
| novalue: "no value", |
| builtin: "built-in", |
| typexpr: "type", |
| constant_: "constant", |
| variable: "variable", |
| mapindex: "map index expression", |
| value: "value", |
| commaok: "comma, ok expression", |
| } |
| |
| // An operand represents an intermediate value during type checking. |
| // Operands have an (addressing) mode, the expression evaluating to |
| // the operand, the operand's type, a value for constants, and an id |
| // for built-in functions. |
| // The zero value of operand is a ready to use invalid operand. |
| // |
| type operand struct { |
| mode operandMode |
| expr ast.Expr |
| typ Type |
| val constant.Value |
| id builtinId |
| } |
| |
| // pos returns the position of the expression corresponding to x. |
| // If x is invalid the position is token.NoPos. |
| // |
| func (x *operand) pos() token.Pos { |
| // x.expr may not be set if x is invalid |
| if x.expr == nil { |
| return token.NoPos |
| } |
| return x.expr.Pos() |
| } |
| |
| // Operand string formats |
| // (not all "untyped" cases can appear due to the type system, |
| // but they fall out naturally here) |
| // |
| // mode format |
| // |
| // invalid <expr> ( <mode> ) |
| // novalue <expr> ( <mode> ) |
| // builtin <expr> ( <mode> ) |
| // typexpr <expr> ( <mode> ) |
| // |
| // constant <expr> (<untyped kind> <mode> ) |
| // constant <expr> ( <mode> of type <typ>) |
| // constant <expr> (<untyped kind> <mode> <val> ) |
| // constant <expr> ( <mode> <val> of type <typ>) |
| // |
| // variable <expr> (<untyped kind> <mode> ) |
| // variable <expr> ( <mode> of type <typ>) |
| // |
| // mapindex <expr> (<untyped kind> <mode> ) |
| // mapindex <expr> ( <mode> of type <typ>) |
| // |
| // value <expr> (<untyped kind> <mode> ) |
| // value <expr> ( <mode> of type <typ>) |
| // |
| // commaok <expr> (<untyped kind> <mode> ) |
| // commaok <expr> ( <mode> of type <typ>) |
| // |
| func operandString(x *operand, qf Qualifier) string { |
| var buf bytes.Buffer |
| |
| var expr string |
| if x.expr != nil { |
| expr = ExprString(x.expr) |
| } else { |
| switch x.mode { |
| case builtin: |
| expr = predeclaredFuncs[x.id].name |
| case typexpr: |
| expr = TypeString(x.typ, qf) |
| case constant_: |
| expr = x.val.String() |
| } |
| } |
| |
| // <expr> ( |
| if expr != "" { |
| buf.WriteString(expr) |
| buf.WriteString(" (") |
| } |
| |
| // <untyped kind> |
| hasType := false |
| switch x.mode { |
| case invalid, novalue, builtin, typexpr: |
| // no type |
| default: |
| // has type |
| if isUntyped(x.typ) { |
| buf.WriteString(x.typ.(*Basic).name) |
| buf.WriteByte(' ') |
| break |
| } |
| hasType = true |
| } |
| |
| // <mode> |
| buf.WriteString(operandModeString[x.mode]) |
| |
| // <val> |
| if x.mode == constant_ { |
| if s := x.val.String(); s != expr { |
| buf.WriteByte(' ') |
| buf.WriteString(s) |
| } |
| } |
| |
| // <typ> |
| if hasType { |
| if x.typ != Typ[Invalid] { |
| buf.WriteString(" of type ") |
| WriteType(&buf, x.typ, qf) |
| } else { |
| buf.WriteString(" with invalid type") |
| } |
| } |
| |
| // ) |
| if expr != "" { |
| buf.WriteByte(')') |
| } |
| |
| return buf.String() |
| } |
| |
| func (x *operand) String() string { |
| return operandString(x, nil) |
| } |
| |
| // setConst sets x to the untyped constant for literal lit. |
| func (x *operand) setConst(tok token.Token, lit string) { |
| val := constant.MakeFromLiteral(lit, tok, 0) |
| if val == nil { |
| // TODO(gri) Should we make it an unknown constant instead? |
| x.mode = invalid |
| return |
| } |
| |
| var kind BasicKind |
| switch tok { |
| case token.INT: |
| kind = UntypedInt |
| case token.FLOAT: |
| kind = UntypedFloat |
| case token.IMAG: |
| kind = UntypedComplex |
| case token.CHAR: |
| kind = UntypedRune |
| case token.STRING: |
| kind = UntypedString |
| } |
| |
| x.mode = constant_ |
| x.typ = Typ[kind] |
| x.val = val |
| } |
| |
| // isNil reports whether x is the nil value. |
| func (x *operand) isNil() bool { |
| return x.mode == value && x.typ == Typ[UntypedNil] |
| } |
| |
| // TODO(gri) The functions operand.assignableTo, checker.convertUntyped, |
| // checker.representable, and checker.assignment are |
| // overlapping in functionality. Need to simplify and clean up. |
| |
| // assignableTo reports whether x is assignable to a variable of type T. |
| func (x *operand) assignableTo(conf *Config, T Type) bool { |
| if x.mode == invalid || T == Typ[Invalid] { |
| return true // avoid spurious errors |
| } |
| |
| V := x.typ |
| |
| // x's type is identical to T |
| if Identical(V, T) { |
| return true |
| } |
| |
| Vu := V.Underlying() |
| Tu := T.Underlying() |
| |
| // T is an interface type and x implements T |
| // (Do this check first as it might succeed early.) |
| if Ti, ok := Tu.(*Interface); ok { |
| if Implements(x.typ, Ti) { |
| return true |
| } |
| } |
| |
| // x's type V and T have identical underlying types |
| // and at least one of V or T is not a named type |
| if Identical(Vu, Tu) && (!isNamed(V) || !isNamed(T)) { |
| return true |
| } |
| |
| // x is a bidirectional channel value, T is a channel |
| // type, x's type V and T have identical element types, |
| // and at least one of V or T is not a named type |
| if Vc, ok := Vu.(*Chan); ok && Vc.dir == SendRecv { |
| if Tc, ok := Tu.(*Chan); ok && Identical(Vc.elem, Tc.elem) { |
| return !isNamed(V) || !isNamed(T) |
| } |
| } |
| |
| // x is the predeclared identifier nil and T is a pointer, |
| // function, slice, map, channel, or interface type |
| if x.isNil() { |
| switch t := Tu.(type) { |
| case *Basic: |
| if t.kind == UnsafePointer { |
| return true |
| } |
| case *Pointer, *Signature, *Slice, *Map, *Chan, *Interface: |
| return true |
| } |
| return false |
| } |
| |
| // x is an untyped constant representable by a value of type T |
| // TODO(gri) This is borrowing from checker.convertUntyped and |
| // checker.representable. Need to clean up. |
| if isUntyped(Vu) { |
| switch t := Tu.(type) { |
| case *Basic: |
| if x.mode == constant_ { |
| return representableConst(x.val, conf, t.kind, nil) |
| } |
| // The result of a comparison is an untyped boolean, |
| // but may not be a constant. |
| if Vb, _ := Vu.(*Basic); Vb != nil { |
| return Vb.kind == UntypedBool && isBoolean(Tu) |
| } |
| case *Interface: |
| return x.isNil() || t.Empty() |
| case *Pointer, *Signature, *Slice, *Map, *Chan: |
| return x.isNil() |
| } |
| } |
| |
| return false |
| } |
| |
| // isInteger reports whether x is value of integer type |
| // or an untyped constant representable as an integer. |
| func (x *operand) isInteger() bool { |
| return x.mode == invalid || |
| isInteger(x.typ) || |
| isUntyped(x.typ) && x.mode == constant_ && representableConst(x.val, nil, UntypedInt, nil) // no *Config required for UntypedInt |
| } |