// 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, true, nil) } // IdenticalIgnoreTags reports whether x and y are identical if tags are ignored. func IdenticalIgnoreTags(x, y Type) bool { return identical(x, y, false, 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, cmpTags bool, 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, cmpTags, 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, cmpTags, 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 || cmpTags && x.Tag(i) != y.Tag(i) || !f.sameId(g.pkg, g.name) || !identical(f.typ, g.typ, cmpTags, 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, cmpTags, 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, cmpTags, 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, cmpTags, p) && identical(x.results, y.results, cmpTags, 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, cmpTags, 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, cmpTags, p) && identical(x.elem, y.elem, cmpTags, 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, cmpTags, 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 } case nil: default: unreachable() } return false } // Default 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 Default(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 }