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:
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.targs == nil && named.TParams() != nil
27 func is(typ Type, what BasicInfo) bool {
28 switch t := under(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 asBasic()!
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 switch t := under(T).(type) {
101 // assume invalid types to be comparable
102 // to avoid follow-up errors
103 return t.kind != UntypedNil
104 case *Pointer, *Interface, *Chan:
107 for _, f := range t.fields {
108 if !comparable(f.typ, seen) {
114 return comparable(t.elem, seen)
116 return t.Bound().IsComparable()
121 // hasNil reports whether a type includes the nil value.
122 func hasNil(typ Type) bool {
123 switch t := under(typ).(type) {
125 return t.kind == UnsafePointer
126 case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan:
129 return t.underIs(hasNil)
134 // An ifacePair is a node in a stack of interface type pairs compared for identity.
135 type ifacePair struct {
140 func (p *ifacePair) identical(q *ifacePair) bool {
141 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
144 // For changes to this code the corresponding changes should be made to unifier.nify.
145 func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
146 // types must be expanded for comparison
154 switch x := x.(type) {
156 // Basic types are singletons except for the rune and byte
157 // aliases, thus we cannot solely rely on the x == y check
158 // above. See also comment in TypeName.IsAlias.
159 if y, ok := y.(*Basic); ok {
160 return x.kind == y.kind
164 // Two array types are identical if they have identical element types
165 // and the same array length.
166 if y, ok := y.(*Array); ok {
167 // If one or both array lengths are unknown (< 0) due to some error,
168 // assume they are the same to avoid spurious follow-on errors.
169 return (x.len < 0 || y.len < 0 || x.len == y.len) && identical(x.elem, y.elem, cmpTags, p)
173 // Two slice types are identical if they have identical element types.
174 if y, ok := y.(*Slice); ok {
175 return identical(x.elem, y.elem, cmpTags, p)
179 // Two struct types are identical if they have the same sequence of fields,
180 // and if corresponding fields have the same names, and identical types,
181 // and identical tags. Two embedded fields are considered to have the same
182 // name. Lower-case field names from different packages are always different.
183 if y, ok := y.(*Struct); ok {
184 if x.NumFields() == y.NumFields() {
185 for i, f := range x.fields {
187 if f.embedded != g.embedded ||
188 cmpTags && x.Tag(i) != y.Tag(i) ||
189 !f.sameId(g.pkg, g.name) ||
190 !identical(f.typ, g.typ, cmpTags, p) {
199 // Two pointer types are identical if they have identical base types.
200 if y, ok := y.(*Pointer); ok {
201 return identical(x.base, y.base, cmpTags, p)
205 // Two tuples types are identical if they have the same number of elements
206 // and corresponding elements have identical types.
207 if y, ok := y.(*Tuple); ok {
208 if x.Len() == y.Len() {
210 for i, v := range x.vars {
212 if !identical(v.typ, w.typ, cmpTags, p) {
222 // Two function types are identical if they have the same number of parameters
223 // and result values, corresponding parameter and result types are identical,
224 // and either both functions are variadic or neither is. Parameter and result
225 // names are not required to match.
226 // Generic functions must also have matching type parameter lists, but for the
228 if y, ok := y.(*Signature); ok {
229 return x.variadic == y.variadic &&
230 identicalTParams(x.tparams, y.tparams, cmpTags, p) &&
231 identical(x.params, y.params, cmpTags, p) &&
232 identical(x.results, y.results, cmpTags, p)
236 // Two union types are identical if they contain the same terms.
237 // The set (list) of types in a union type consists of unique
238 // types - each type appears exactly once. Thus, two union types
239 // must contain the same number of types to have chance of
241 if y, ok := y.(*Union); ok && x.NumTerms() == y.NumTerms() {
242 // Every type in x.types must be in y.types.
243 // Quadratic algorithm, but probably good enough for now.
244 // TODO(gri) we need a fast quick type ID/hash for all types.
246 for i, xt := range x.types {
247 for j, yt := range y.types {
248 if Identical(xt, yt) && x.tilde[i] == y.tilde[j] {
249 continue L // x is in y.types
252 return false // x is not in y.types
258 // Two interface types are identical if they describe the same type sets.
259 // With the existing implementation restriction, this simplifies to:
261 // Two interface types are identical if they have the same set of methods with
262 // the same names and identical function types, and if any type restrictions
263 // are the same. Lower-case method names from different packages are always
264 // different. The order of the methods is irrelevant.
265 if y, ok := y.(*Interface); ok {
268 if !Identical(xset.types, yset.types) {
273 if len(a) == len(b) {
274 // Interface types are the only types where cycles can occur
275 // that are not "terminated" via named types; and such cycles
276 // can only be created via method parameter types that are
277 // anonymous interfaces (directly or indirectly) embedding
278 // the current interface. Example:
280 // type T interface {
284 // If two such (differently named) interfaces are compared,
285 // endless recursion occurs if the cycle is not detected.
287 // If x and y were compared before, they must be equal
288 // (if they were not, the recursion would have stopped);
289 // search the ifacePair stack for the same pair.
291 // This is a quadratic algorithm, but in practice these stacks
292 // are extremely short (bounded by the nesting depth of interface
293 // type declarations that recur via parameter types, an extremely
294 // rare occurrence). An alternative implementation might use a
295 // "visited" map, but that is probably less efficient overall.
296 q := &ifacePair{x, y, p}
299 return true // same pair was compared before
304 assertSortedMethods(a)
305 assertSortedMethods(b)
307 for i, f := range a {
309 if f.Id() != g.Id() || !identical(f.typ, g.typ, cmpTags, q) {
318 // Two map types are identical if they have identical key and value types.
319 if y, ok := y.(*Map); ok {
320 return identical(x.key, y.key, cmpTags, p) && identical(x.elem, y.elem, cmpTags, p)
324 // Two channel types are identical if they have identical value types
325 // and the same direction.
326 if y, ok := y.(*Chan); ok {
327 return x.dir == y.dir && identical(x.elem, y.elem, cmpTags, p)
331 // Two named types are identical if their type names originate
332 // in the same type declaration.
333 if y, ok := y.(*Named); ok {
334 // TODO(gri) Why is x == y not sufficient? And if it is,
335 // we can just return false here because x == y
336 // is caught in the very beginning of this function.
337 return x.obj == y.obj
341 // nothing to do (x and y being equal is caught in the very beginning of this function)
344 // unreachable since types are expanded
347 // Either both types are theTop in which case the initial x == y check
348 // will have caught them. Otherwise they are not identical.
351 // avoid a crash in case of nil type
360 func identicalTParams(x, y []*TypeName, cmpTags bool, p *ifacePair) bool {
361 if len(x) != len(y) {
364 for i, x := range x {
366 if !identical(x.typ.(*TypeParam).bound, y.typ.(*TypeParam).bound, cmpTags, p) {
373 // Default returns the default "typed" type for an "untyped" type;
374 // it returns the incoming type for all other types. The default type
375 // for untyped nil is untyped nil.
377 func Default(typ Type) Type {
378 if t, ok := typ.(*Basic); ok {
385 return universeRune // use 'rune' name
389 return Typ[Complex128]