golang predicates 代码
文件路径：/src/cmd/compile/internal/types2/predicates.go
/ 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 types2
/ The isX predicates below report whether t is an X.
/ If t is a type parameter the result is false; i.e.,
/ these predicates don't look inside a type parameter.
func isBoolean(t Type) bool { return isBasic(t, IsBoolean) }
func isInteger(t Type) bool { return isBasic(t, IsInteger) }
func isUnsigned(t Type) bool { return isBasic(t, IsUnsigned) }
func isFloat(t Type) bool { return isBasic(t, IsFloat) }
func isComplex(t Type) bool { return isBasic(t, IsComplex) }
func isNumeric(t Type) bool { return isBasic(t, IsNumeric) }
func isString(t Type) bool { return isBasic(t, IsString) }
func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) }
func isConstType(t Type) bool { return isBasic(t, IsConstType) }
/ isBasic reports whether under(t) is a basic type with the specified info.
/ If t is a type parameter the result is false; i.e.,
/ isBasic does not look inside a type parameter.
func isBasic(t Type, info BasicInfo) bool {
u, _ := under(t).(*Basic)
return u != nil && u.info&info != 0
}
/ The allX predicates below report whether t is an X.
/ If t is a type parameter the result is true if isX is true
/ for all specified types of the type parameter's type set.
/ allX is an optimized version of isX(coreType(t)) (which
/ is the same as underIs(t, isX)).
func allBoolean(t Type) bool { return allBasic(t, IsBoolean) }
func allInteger(t Type) bool { return allBasic(t, IsInteger) }
func allUnsigned(t Type) bool { return allBasic(t, IsUnsigned) }
func allNumeric(t Type) bool { return allBasic(t, IsNumeric) }
func allString(t Type) bool { return allBasic(t, IsString) }
func allOrdered(t Type) bool { return allBasic(t, IsOrdered) }
func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) }
/ allBasic reports whether under(t) is a basic type with the specified info.
/ If t is a type parameter, the result is true if isBasic(t, info) is true
/ for all specific types of the type parameter's type set.
/ allBasic(t, info) is an optimized version of isBasic(coreType(t), info).
func allBasic(t Type, info BasicInfo) bool {
if tpar, _ := t.(*TypeParam); tpar != nil {
return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) })
}
return isBasic(t, info)
}
/ hasName reports whether t has a name. This includes
/ predeclared types, defined types, and type parameters.
/ hasName may be called with types that are not fully set up.
func hasName(t Type) bool {
switch t.(type) {
case *Basic, *Named, *TypeParam:
return true
}
return false
}
/ isTyped reports whether t is typed; i.e., not an untyped
/ constant or boolean. isTyped may be called with types that
/ are not fully set up.
func isTyped(t Type) bool {
/ isTyped is called with types that are not fully
/ set up. Must not call under()!
b, _ := t.(*Basic)
return b == nil || b.info&IsUntyped == 0
}
/ isUntyped(t) is the same as !isTyped(t).
func isUntyped(t Type) bool {
return !isTyped(t)
}
/ IsInterface reports whether t is an interface type.
func IsInterface(t Type) bool {
_, ok := under(t).(*Interface)
return ok
}
/ isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
func isNonTypeParamInterface(t Type) bool {
return !isTypeParam(t) && IsInterface(t)
}
/ isTypeParam reports whether t is a type parameter.
func isTypeParam(t Type) bool {
_, ok := t.(*TypeParam)
return ok
}
/ isGeneric reports whether a type is a generic, uninstantiated type
/ (generic signatures are not included).
/ TODO(gri) should we include signatures or assert that they are not present?
func isGeneric(t Type) bool {
/ A parameterized type is only generic if it doesn't have an instantiation already.
named, _ := t.(*Named)
return named != nil && named.obj != nil && named.inst == nil && named.TypeParams().Len() > 0
}
/ Comparable reports whether values of type T are comparable.
func Comparable(T Type) bool {
return comparable(T, true, nil, nil)
}
/ If dynamic is set, non-type parameter interfaces are always comparable.
/ If reportf != nil, it may be used to report why T is not comparable.
func comparable(T Type, dynamic bool, seen map[Type]bool, reportf func(string, ...interface{})) bool {
if seen[T] {
return true
}
if seen == nil {
seen = make(map[Type]bool)
}
seen[T] = true
switch t := under(T).(type) {
case *Basic:
/ assume invalid types to be comparable
/ to avoid follow-up errors
return t.kind != UntypedNil
case *Pointer, *Chan:
return true
case *Struct:
for _, f := range t.fields {
if !comparable(f.typ, dynamic, seen, nil) {
if reportf != nil {
reportf("struct containing %s cannot be compared", f.typ)
}
return false
}
}
return true
case *Array:
if !comparable(t.elem, dynamic, seen, nil) {
if reportf != nil {
reportf("%s cannot be compared", t)
}
return false
}
return true
case *Interface:
if dynamic && !isTypeParam(T) || t.typeSet().IsComparable(seen) {
return true
}
if reportf != nil {
if t.typeSet().IsEmpty() {
reportf("empty type set")
} else {
reportf("incomparable types in type set")
}
}
/ fallthrough
}
return false
}
/ hasNil reports whether type t includes the nil value.
func hasNil(t Type) bool {
switch u := under(t).(type) {
case *Basic:
return u.kind == UnsafePointer
case *Slice, *Pointer, *Signature, *Map, *Chan:
return true
case *Interface:
return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool {
return u != nil && hasNil(u)
})
}
return false
}
/ 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
}
/ For changes to this code the corresponding changes should be made to unifier.nify.
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. See also comment in TypeName.IsAlias.
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 {
/ If one or both array lengths are unknown (< 0) due to some error,
/ assume they are the same to avoid spurious follow-on errors.
return (x.len < 0 || y.len < 0 || 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 embedded 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.embedded != g.embedded ||
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:
y, _ := y.(*Signature)
if y == nil {
return false
}
/ 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, and type
/ parameters are considered identical modulo renaming.
if x.TypeParams().Len() != y.TypeParams().Len() {
return false
}
/ In the case of generic signatures, we will substitute in yparams and
/ yresults.
yparams := y.params
yresults := y.results
if x.TypeParams().Len() > 0 {
/ We must ignore type parameter names when comparing x and y. The
/ easiest way to do this is to substitute x's type parameters for y's.
xtparams := x.TypeParams().list()
ytparams := y.TypeParams().list()
var targs []Type
for i := range xtparams {
targs = append(targs, x.TypeParams().At(i))
}
smap := makeSubstMap(ytparams, targs)
var check *Checker / ok to call subst on a nil *Checker
ctxt := NewContext() / need a non-nil Context for the substitution below
/ Constraints must be pair-wise identical, after substitution.
for i, xtparam := range xtparams {
ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt)
if !identical(xtparam.bound, ybound, cmpTags, p) {
return false
}
}
yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple)
yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple)
}
return x.variadic == y.variadic &&
identical(x.params, yparams, cmpTags, p) &&
identical(x.results, yresults, cmpTags, p)
case *Union:
if y, _ := y.(*Union); y != nil {
/ TODO(rfindley): can this be reached during type checking? If so,
/ consider passing a type set map.
unionSets := make(map[*Union]*_TypeSet)
xset := computeUnionTypeSet(nil, unionSets, nopos, x)
yset := computeUnionTypeSet(nil, unionSets, nopos, y)
return xset.terms.equal(yset.terms)
}
case *Interface:
/ Two interface types are identical if they describe the same type sets.
/ With the existing implementation restriction, this simplifies to:
/
/ Two interface types are identical if they have the same set of methods with
/ the same names and identical function types, and if any type restrictions
/ are the same. Lower-case method names from different packages are always
/ different. The order of the methods is irrelevant.
if y, ok := y.(*Interface); ok {
xset := x.typeSet()
yset := y.typeSet()
if xset.comparable != yset.comparable {
return false
}
if !xset.terms.equal(yset.terms) {
return false
}
a := xset.methods
b := yset.methods
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 {
assertSortedMethods(a)
assertSortedMethods(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 {
xargs := x.TypeArgs().list()
yargs := y.TypeArgs().list()
if len(xargs) != len(yargs) {
return false
}
if len(xargs) > 0 {
/ Instances are identical if their original type and type arguments
/ are identical.
if !Identical(x.Origin(), y.Origin()) {
return false
}
for i, xa := range xargs {
if !Identical(xa, yargs[i]) {
return false
}
}
return true
}
/ TODO(gri) Why is x == y not sufficient? And if it is,
/ we can just return false here because x == y
/ is caught in the very beginning of this function.
return x.obj == y.obj
}
case *TypeParam:
/ nothing to do (x and y being equal is caught in the very beginning of this function)
case nil:
/ avoid a crash in case of nil type
default:
unreachable()
}
return false
}
/ identicalInstance reports if two type instantiations are identical.
/ Instantiations are identical if their origin and type arguments are
/ identical.
func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool {
if len(xargs) != len(yargs) {
return false
}
for i, xa := range xargs {
if !Identical(xa, yargs[i]) {
return false
}
}
return Identical(xorig, yorig)
}
/ 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(t Type) Type {
if t, ok := t.(*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 t
}