| // 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 commonly used type predicates. |
| |
| package types |
| |
| import "sort" |
| |
| func isNamed(typ Type) bool { |
| if _, ok := typ.(*Basic); ok { |
| return ok |
| } |
| _, ok := typ.(*Named) |
| return ok |
| } |
| |
| func isBoolean(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsBoolean != 0 |
| } |
| |
| func isInteger(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsInteger != 0 |
| } |
| |
| func isUnsigned(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsUnsigned != 0 |
| } |
| |
| func isFloat(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsFloat != 0 |
| } |
| |
| func isComplex(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsComplex != 0 |
| } |
| |
| func isNumeric(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsNumeric != 0 |
| } |
| |
| func isString(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsString != 0 |
| } |
| |
| func isTyped(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return !ok || t.info&IsUntyped == 0 |
| } |
| |
| func isUntyped(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsUntyped != 0 |
| } |
| |
| func isOrdered(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsOrdered != 0 |
| } |
| |
| func isConstType(typ Type) bool { |
| t, ok := typ.Underlying().(*Basic) |
| return ok && t.info&IsConstType != 0 |
| } |
| |
| // IsInterface reports whether typ is an interface type. |
| func IsInterface(typ Type) bool { |
| _, ok := typ.Underlying().(*Interface) |
| return ok |
| } |
| |
| // Comparable reports whether values of type T are comparable. |
| func Comparable(T Type) bool { |
| switch t := T.Underlying().(type) { |
| case *Basic: |
| // assume invalid types to be comparable |
| // to avoid follow-up errors |
| return t.kind != UntypedNil |
| case *Pointer, *Interface, *Chan: |
| return true |
| case *Struct: |
| for _, f := range t.fields { |
| if !Comparable(f.typ) { |
| return false |
| } |
| } |
| return true |
| case *Array: |
| return Comparable(t.elem) |
| } |
| return false |
| } |
| |
| // hasNil reports whether a type includes the nil value. |
| func hasNil(typ Type) bool { |
| switch t := typ.Underlying().(type) { |
| case *Basic: |
| return t.kind == UnsafePointer |
| case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan: |
| return true |
| } |
| return false |
| } |
| |
| // Identical reports whether x and y are identical. |
| func Identical(x, y Type) bool { |
| return identical(x, y, nil) |
| } |
| |
| // An ifacePair is a node in a stack of interface type pairs compared for identity. |
| type ifacePair struct { |
| x, y *Interface |
| prev *ifacePair |
| } |
| |
| func (p *ifacePair) identical(q *ifacePair) bool { |
| return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x |
| } |
| |
| func identical(x, y Type, p *ifacePair) bool { |
| if x == y { |
| return true |
| } |
| |
| switch x := x.(type) { |
| case *Basic: |
| // Basic types are singletons except for the rune and byte |
| // aliases, thus we cannot solely rely on the x == y check |
| // above. |
| if y, ok := y.(*Basic); ok { |
| return x.kind == y.kind |
| } |
| |
| case *Array: |
| // Two array types are identical if they have identical element types |
| // and the same array length. |
| if y, ok := y.(*Array); ok { |
| return x.len == y.len && identical(x.elem, y.elem, p) |
| } |
| |
| case *Slice: |
| // Two slice types are identical if they have identical element types. |
| if y, ok := y.(*Slice); ok { |
| return identical(x.elem, y.elem, p) |
| } |
| |
| case *Struct: |
| // Two struct types are identical if they have the same sequence of fields, |
| // and if corresponding fields have the same names, and identical types, |
| // and identical tags. Two anonymous fields are considered to have the same |
| // name. Lower-case field names from different packages are always different. |
| if y, ok := y.(*Struct); ok { |
| if x.NumFields() == y.NumFields() { |
| for i, f := range x.fields { |
| g := y.fields[i] |
| if f.anonymous != g.anonymous || |
| x.Tag(i) != y.Tag(i) || |
| !f.sameId(g.pkg, g.name) || |
| !identical(f.typ, g.typ, p) { |
| return false |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Pointer: |
| // Two pointer types are identical if they have identical base types. |
| if y, ok := y.(*Pointer); ok { |
| return identical(x.base, y.base, p) |
| } |
| |
| case *Tuple: |
| // Two tuples types are identical if they have the same number of elements |
| // and corresponding elements have identical types. |
| if y, ok := y.(*Tuple); ok { |
| if x.Len() == y.Len() { |
| if x != nil { |
| for i, v := range x.vars { |
| w := y.vars[i] |
| if !identical(v.typ, w.typ, p) { |
| return false |
| } |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Signature: |
| // Two function types are identical if they have the same number of parameters |
| // and result values, corresponding parameter and result types are identical, |
| // and either both functions are variadic or neither is. Parameter and result |
| // names are not required to match. |
| if y, ok := y.(*Signature); ok { |
| return x.variadic == y.variadic && |
| identical(x.params, y.params, p) && |
| identical(x.results, y.results, p) |
| } |
| |
| case *Interface: |
| // Two interface types are identical if they have the same set of methods with |
| // the same names and identical function types. Lower-case method names from |
| // different packages are always different. The order of the methods is irrelevant. |
| if y, ok := y.(*Interface); ok { |
| a := x.allMethods |
| b := y.allMethods |
| if len(a) == len(b) { |
| // Interface types are the only types where cycles can occur |
| // that are not "terminated" via named types; and such cycles |
| // can only be created via method parameter types that are |
| // anonymous interfaces (directly or indirectly) embedding |
| // the current interface. Example: |
| // |
| // type T interface { |
| // m() interface{T} |
| // } |
| // |
| // If two such (differently named) interfaces are compared, |
| // endless recursion occurs if the cycle is not detected. |
| // |
| // If x and y were compared before, they must be equal |
| // (if they were not, the recursion would have stopped); |
| // search the ifacePair stack for the same pair. |
| // |
| // This is a quadratic algorithm, but in practice these stacks |
| // are extremely short (bounded by the nesting depth of interface |
| // type declarations that recur via parameter types, an extremely |
| // rare occurrence). An alternative implementation might use a |
| // "visited" map, but that is probably less efficient overall. |
| q := &ifacePair{x, y, p} |
| for p != nil { |
| if p.identical(q) { |
| return true // same pair was compared before |
| } |
| p = p.prev |
| } |
| if debug { |
| assert(sort.IsSorted(byUniqueMethodName(a))) |
| assert(sort.IsSorted(byUniqueMethodName(b))) |
| } |
| for i, f := range a { |
| g := b[i] |
| if f.Id() != g.Id() || !identical(f.typ, g.typ, q) { |
| return false |
| } |
| } |
| return true |
| } |
| } |
| |
| case *Map: |
| // Two map types are identical if they have identical key and value types. |
| if y, ok := y.(*Map); ok { |
| return identical(x.key, y.key, p) && identical(x.elem, y.elem, p) |
| } |
| |
| case *Chan: |
| // Two channel types are identical if they have identical value types |
| // and the same direction. |
| if y, ok := y.(*Chan); ok { |
| return x.dir == y.dir && identical(x.elem, y.elem, p) |
| } |
| |
| case *Named: |
| // Two named types are identical if their type names originate |
| // in the same type declaration. |
| if y, ok := y.(*Named); ok { |
| return x.obj == y.obj |
| } |
| |
| default: |
| unreachable() |
| } |
| |
| return false |
| } |
| |
| // defaultType returns the default "typed" type for an "untyped" type; |
| // it returns the incoming type for all other types. The default type |
| // for untyped nil is untyped nil. |
| // |
| func defaultType(typ Type) Type { |
| if t, ok := typ.(*Basic); ok { |
| switch t.kind { |
| case UntypedBool: |
| return Typ[Bool] |
| case UntypedInt: |
| return Typ[Int] |
| case UntypedRune: |
| return universeRune // use 'rune' name |
| case UntypedFloat: |
| return Typ[Float64] |
| case UntypedComplex: |
| return Typ[Complex128] |
| case UntypedString: |
| return Typ[String] |
| } |
| } |
| return typ |
| } |