1 // Copyright 2012 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // This file implements commonly used type predicates.
9 // isNamed reports whether typ has a name.
10 // isNamed may be called with types that are not fully set up.
11 func isNamed(typ Type) bool {
13 case *Basic, *Named, *TypeParam, *instance:
19 // isGeneric reports whether a type is a generic, uninstantiated type (generic
20 // signatures are not included).
21 func isGeneric(typ Type) bool {
22 // A parameterized type is only instantiated if it doesn't have an instantiation already.
23 named, _ := typ.(*Named)
24 return named != nil && named.obj != nil && named.TParams() != nil && named.targs == nil
27 func is(typ Type, what BasicInfo) bool {
28 switch t := optype(typ).(type) {
30 return t.info&what != 0
32 return t.underIs(func(t Type) bool { return is(t, what) })
37 func isBoolean(typ Type) bool { return is(typ, IsBoolean) }
38 func isInteger(typ Type) bool { return is(typ, IsInteger) }
39 func isUnsigned(typ Type) bool { return is(typ, IsUnsigned) }
40 func isFloat(typ Type) bool { return is(typ, IsFloat) }
41 func isComplex(typ Type) bool { return is(typ, IsComplex) }
42 func isNumeric(typ Type) bool { return is(typ, IsNumeric) }
43 func isString(typ Type) bool { return is(typ, IsString) }
45 // Note that if typ is a type parameter, isInteger(typ) || isFloat(typ) does not
46 // produce the expected result because a type list that contains both an integer
47 // and a floating-point type is neither (all) integers, nor (all) floats.
48 // Use isIntegerOrFloat instead.
49 func isIntegerOrFloat(typ Type) bool { return is(typ, IsInteger|IsFloat) }
51 // isNumericOrString is the equivalent of isIntegerOrFloat for isNumeric(typ) || isString(typ).
52 func isNumericOrString(typ Type) bool { return is(typ, IsNumeric|IsString) }
54 // isTyped reports whether typ is typed; i.e., not an untyped
55 // constant or boolean. isTyped may be called with types that
56 // are not fully set up.
57 func isTyped(typ Type) bool {
58 // isTyped is called with types that are not fully
59 // set up. Must not call Basic()!
60 // A *Named or *instance type is always typed, so
61 // we only need to check if we have a true *Basic
64 return t == nil || t.info&IsUntyped == 0
67 // isUntyped(typ) is the same as !isTyped(typ).
68 func isUntyped(typ Type) bool {
72 func isOrdered(typ Type) bool { return is(typ, IsOrdered) }
74 func isConstType(typ Type) bool {
75 // Type parameters are never const types.
76 t, _ := under(typ).(*Basic)
77 return t != nil && t.info&IsConstType != 0
80 // IsInterface reports whether typ is an interface type.
81 func IsInterface(typ Type) bool {
82 return asInterface(typ) != nil
85 // Comparable reports whether values of type T are comparable.
86 func Comparable(T Type) bool {
87 return comparable(T, nil)
90 func comparable(T Type, seen map[Type]bool) bool {
95 seen = make(map[Type]bool)
99 // If T is a type parameter not constrained by any type
100 // list (i.e., it's operational type is the top type),
101 // T is comparable if it has the == method. Otherwise,
102 // the operational type "wins". For instance
104 // interface{ comparable; type []byte }
106 // is not comparable because []byte is not comparable.
107 if t := asTypeParam(T); t != nil && optype(t) == theTop {
108 return t.Bound().IsComparable()
111 switch t := optype(T).(type) {
113 // assume invalid types to be comparable
114 // to avoid follow-up errors
115 return t.kind != UntypedNil
116 case *Pointer, *Interface, *Chan:
119 for _, f := range t.fields {
120 if !comparable(f.typ, seen) {
126 return comparable(t.elem, seen)
128 return t.underIs(func(t Type) bool {
129 return comparable(t, seen)
132 return t.Bound().IsComparable()
137 // hasNil reports whether a type includes the nil value.
138 func hasNil(typ Type) bool {
139 switch t := optype(typ).(type) {
141 return t.kind == UnsafePointer
142 case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan:
145 return t.underIs(hasNil)
150 // An ifacePair is a node in a stack of interface type pairs compared for identity.
151 type ifacePair struct {
156 func (p *ifacePair) identical(q *ifacePair) bool {
157 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
160 // For changes to this code the corresponding changes should be made to unifier.nify.
161 func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
162 // types must be expanded for comparison
170 switch x := x.(type) {
172 // Basic types are singletons except for the rune and byte
173 // aliases, thus we cannot solely rely on the x == y check
174 // above. See also comment in TypeName.IsAlias.
175 if y, ok := y.(*Basic); ok {
176 return x.kind == y.kind
180 // Two array types are identical if they have identical element types
181 // and the same array length.
182 if y, ok := y.(*Array); ok {
183 // If one or both array lengths are unknown (< 0) due to some error,
184 // assume they are the same to avoid spurious follow-on errors.
185 return (x.len < 0 || y.len < 0 || x.len == y.len) && identical(x.elem, y.elem, cmpTags, p)
189 // Two slice types are identical if they have identical element types.
190 if y, ok := y.(*Slice); ok {
191 return identical(x.elem, y.elem, cmpTags, p)
195 // Two struct types are identical if they have the same sequence of fields,
196 // and if corresponding fields have the same names, and identical types,
197 // and identical tags. Two embedded fields are considered to have the same
198 // name. Lower-case field names from different packages are always different.
199 if y, ok := y.(*Struct); ok {
200 if x.NumFields() == y.NumFields() {
201 for i, f := range x.fields {
203 if f.embedded != g.embedded ||
204 cmpTags && x.Tag(i) != y.Tag(i) ||
205 !f.sameId(g.pkg, g.name) ||
206 !identical(f.typ, g.typ, cmpTags, p) {
215 // Two pointer types are identical if they have identical base types.
216 if y, ok := y.(*Pointer); ok {
217 return identical(x.base, y.base, cmpTags, p)
221 // Two tuples types are identical if they have the same number of elements
222 // and corresponding elements have identical types.
223 if y, ok := y.(*Tuple); ok {
224 if x.Len() == y.Len() {
226 for i, v := range x.vars {
228 if !identical(v.typ, w.typ, cmpTags, p) {
238 // Two function types are identical if they have the same number of parameters
239 // and result values, corresponding parameter and result types are identical,
240 // and either both functions are variadic or neither is. Parameter and result
241 // names are not required to match.
242 // Generic functions must also have matching type parameter lists, but for the
244 if y, ok := y.(*Signature); ok {
245 return x.variadic == y.variadic &&
246 identicalTParams(x.tparams, y.tparams, cmpTags, p) &&
247 identical(x.params, y.params, cmpTags, p) &&
248 identical(x.results, y.results, cmpTags, p)
252 // Two union types are identical if they contain the same terms.
253 // The set (list) of types in a union type consists of unique
254 // types - each type appears exactly once. Thus, two union types
255 // must contain the same number of types to have chance of
257 if y, ok := y.(*Union); ok && x.NumTerms() == y.NumTerms() {
258 // Every type in x.types must be in y.types.
259 // Quadratic algorithm, but probably good enough for now.
260 // TODO(gri) we need a fast quick type ID/hash for all types.
262 for i, xt := range x.types {
263 for j, yt := range y.types {
264 if Identical(xt, yt) && x.tilde[i] == y.tilde[j] {
265 continue L // x is in y.types
268 return false // x is not in y.types
274 // Two interface types are identical if they have the same set of methods with
275 // the same names and identical function types. Lower-case method names from
276 // different packages are always different. The order of the methods is irrelevant.
277 if y, ok := y.(*Interface); ok {
278 a := x.typeSet().methods
279 b := y.typeSet().methods
280 if len(a) == len(b) {
281 // Interface types are the only types where cycles can occur
282 // that are not "terminated" via named types; and such cycles
283 // can only be created via method parameter types that are
284 // anonymous interfaces (directly or indirectly) embedding
285 // the current interface. Example:
287 // type T interface {
291 // If two such (differently named) interfaces are compared,
292 // endless recursion occurs if the cycle is not detected.
294 // If x and y were compared before, they must be equal
295 // (if they were not, the recursion would have stopped);
296 // search the ifacePair stack for the same pair.
298 // This is a quadratic algorithm, but in practice these stacks
299 // are extremely short (bounded by the nesting depth of interface
300 // type declarations that recur via parameter types, an extremely
301 // rare occurrence). An alternative implementation might use a
302 // "visited" map, but that is probably less efficient overall.
303 q := &ifacePair{x, y, p}
306 return true // same pair was compared before
311 assertSortedMethods(a)
312 assertSortedMethods(b)
314 for i, f := range a {
316 if f.Id() != g.Id() || !identical(f.typ, g.typ, cmpTags, q) {
325 // Two map types are identical if they have identical key and value types.
326 if y, ok := y.(*Map); ok {
327 return identical(x.key, y.key, cmpTags, p) && identical(x.elem, y.elem, cmpTags, p)
331 // Two channel types are identical if they have identical value types
332 // and the same direction.
333 if y, ok := y.(*Chan); ok {
334 return x.dir == y.dir && identical(x.elem, y.elem, cmpTags, p)
338 // Two named types are identical if their type names originate
339 // in the same type declaration.
340 if y, ok := y.(*Named); ok {
341 // TODO(gri) Why is x == y not sufficient? And if it is,
342 // we can just return false here because x == y
343 // is caught in the very beginning of this function.
344 return x.obj == y.obj
348 // nothing to do (x and y being equal is caught in the very beginning of this function)
351 // unreachable since types are expanded
354 // Either both types are theTop in which case the initial x == y check
355 // will have caught them. Otherwise they are not identical.
358 // avoid a crash in case of nil type
367 func identicalTParams(x, y []*TypeName, cmpTags bool, p *ifacePair) bool {
368 if len(x) != len(y) {
371 for i, x := range x {
373 if !identical(x.typ.(*TypeParam).bound, y.typ.(*TypeParam).bound, cmpTags, p) {
380 // Default returns the default "typed" type for an "untyped" type;
381 // it returns the incoming type for all other types. The default type
382 // for untyped nil is untyped nil.
384 func Default(typ Type) Type {
385 if t, ok := typ.(*Basic); ok {
392 return universeRune // use 'rune' name
396 return Typ[Complex128]