| // 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" |
| "fmt" |
| "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 |
| commaerr // like commaok, but second value is error, not boolean |
| cgofunc // operand is a cgo function |
| ) |
| |
| 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", |
| commaerr: "comma, error expression", |
| cgofunc: "cgo function", |
| } |
| |
| // 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>) |
| // |
| // commaerr <expr> (<untyped kind> <mode> ) |
| // commaerr <expr> ( <mode> of type <typ>) |
| // |
| // cgofunc <expr> (<untyped kind> <mode> ) |
| // cgofunc <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: |
| // should have a type, but be cautious (don't crash during printing) |
| if x.typ != nil { |
| 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) { |
| 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 |
| default: |
| unreachable() |
| } |
| |
| val := constant.MakeFromLiteral(lit, tok, 0) |
| if val.Kind() == constant.Unknown { |
| x.mode = invalid |
| x.typ = Typ[Invalid] |
| return |
| } |
| 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] |
| } |
| |
| // assignableTo reports whether x is assignable to a variable of type T. If the |
| // result is false and a non-nil reason is provided, it may be set to a more |
| // detailed explanation of the failure (result != ""). The check parameter may |
| // be nil if assignableTo is invoked through an exported API call, i.e., when |
| // all methods have been type-checked. |
| func (x *operand) assignableTo(check *Checker, T Type, reason *string) (bool, errorCode) { |
| if x.mode == invalid || T == Typ[Invalid] { |
| return true, 0 // avoid spurious errors |
| } |
| |
| V := x.typ |
| |
| // x's type is identical to T |
| if check.identical(V, T) { |
| return true, 0 |
| } |
| |
| Vu := V.Underlying() |
| Tu := T.Underlying() |
| |
| // x is an untyped value representable by a value of type T. |
| if isUntyped(Vu) { |
| if t, ok := Tu.(*Basic); ok && x.mode == constant_ { |
| return representableConst(x.val, check, t, nil), _IncompatibleAssign |
| } |
| return check.implicitType(x, Tu) != nil, _IncompatibleAssign |
| } |
| // Vu is typed |
| |
| // x's type V and T have identical underlying types and at least one of V or |
| // T is not a named type. |
| if check.identical(Vu, Tu) && (!isNamed(V) || !isNamed(T)) { |
| return true, 0 |
| } |
| |
| // T is an interface type and x implements T |
| if Ti, ok := Tu.(*Interface); ok { |
| if m, wrongType := check.missingMethod(V, Ti, true); m != nil /* Implements(V, Ti) */ { |
| if reason != nil { |
| if wrongType != nil { |
| if check.identical(m.typ, wrongType.typ) { |
| *reason = fmt.Sprintf("missing method %s (%s has pointer receiver)", m.name, m.name) |
| } else { |
| *reason = fmt.Sprintf("wrong type for method %s (have %s, want %s)", m.Name(), wrongType.typ, m.typ) |
| } |
| |
| } else { |
| *reason = "missing method " + m.Name() |
| } |
| } |
| return false, _InvalidIfaceAssign |
| } |
| return true, 0 |
| } |
| |
| // 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 && check.identical(Vc.elem, Tc.elem) { |
| if !isNamed(V) || !isNamed(T) { |
| return true, 0 |
| } else { |
| return false, _InvalidChanAssign |
| } |
| } |
| } |
| |
| return false, _IncompatibleAssign |
| } |