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.is(func(typ Type) bool { return is(typ, 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 underlying type is the top type),
101 // T is comparable if it has the == method. Otherwise,
102 // the underlying 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 pred := func(t Type) bool {
129 return comparable(t, seen)
133 return t.Bound().IsComparable()
138 // hasNil reports whether a type includes the nil value.
139 func hasNil(typ Type) bool {
140 switch t := optype(typ).(type) {
142 return t.kind == UnsafePointer
143 case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan:
151 // identical reports whether x and y are identical types.
152 // Receivers of Signature types are ignored.
153 func (check *Checker) identical(x, y Type) bool {
154 return check.identical0(x, y, true, nil)
157 // identicalIgnoreTags reports whether x and y are identical types if tags are ignored.
158 // Receivers of Signature types are ignored.
159 func (check *Checker) identicalIgnoreTags(x, y Type) bool {
160 return check.identical0(x, y, false, nil)
163 // An ifacePair is a node in a stack of interface type pairs compared for identity.
164 type ifacePair struct {
169 func (p *ifacePair) identical(q *ifacePair) bool {
170 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
173 // For changes to this code the corresponding changes should be made to unifier.nify.
174 func (check *Checker) identical0(x, y Type, cmpTags bool, p *ifacePair) bool {
175 // types must be expanded for comparison
183 switch x := x.(type) {
185 // Basic types are singletons except for the rune and byte
186 // aliases, thus we cannot solely rely on the x == y check
187 // above. See also comment in TypeName.IsAlias.
188 if y, ok := y.(*Basic); ok {
189 return x.kind == y.kind
193 // Two array types are identical if they have identical element types
194 // and the same array length.
195 if y, ok := y.(*Array); ok {
196 // If one or both array lengths are unknown (< 0) due to some error,
197 // assume they are the same to avoid spurious follow-on errors.
198 return (x.len < 0 || y.len < 0 || x.len == y.len) && check.identical0(x.elem, y.elem, cmpTags, p)
202 // Two slice types are identical if they have identical element types.
203 if y, ok := y.(*Slice); ok {
204 return check.identical0(x.elem, y.elem, cmpTags, p)
208 // Two struct types are identical if they have the same sequence of fields,
209 // and if corresponding fields have the same names, and identical types,
210 // and identical tags. Two embedded fields are considered to have the same
211 // name. Lower-case field names from different packages are always different.
212 if y, ok := y.(*Struct); ok {
213 if x.NumFields() == y.NumFields() {
214 for i, f := range x.fields {
216 if f.embedded != g.embedded ||
217 cmpTags && x.Tag(i) != y.Tag(i) ||
218 !f.sameId(g.pkg, g.name) ||
219 !check.identical0(f.typ, g.typ, cmpTags, p) {
228 // Two pointer types are identical if they have identical base types.
229 if y, ok := y.(*Pointer); ok {
230 return check.identical0(x.base, y.base, cmpTags, p)
234 // Two tuples types are identical if they have the same number of elements
235 // and corresponding elements have identical types.
236 if y, ok := y.(*Tuple); ok {
237 if x.Len() == y.Len() {
239 for i, v := range x.vars {
241 if !check.identical0(v.typ, w.typ, cmpTags, p) {
251 // Two function types are identical if they have the same number of parameters
252 // and result values, corresponding parameter and result types are identical,
253 // and either both functions are variadic or neither is. Parameter and result
254 // names are not required to match.
255 // Generic functions must also have matching type parameter lists, but for the
257 if y, ok := y.(*Signature); ok {
258 return x.variadic == y.variadic &&
259 check.identicalTParams(x.tparams, y.tparams, cmpTags, p) &&
260 check.identical0(x.params, y.params, cmpTags, p) &&
261 check.identical0(x.results, y.results, cmpTags, p)
265 // Two sum types are identical if they contain the same types.
266 // (Sum types always consist of at least two types. Also, the
267 // the set (list) of types in a sum type consists of unique
268 // types - each type appears exactly once. Thus, two sum types
269 // must contain the same number of types to have chance of
271 if y, ok := y.(*Sum); ok && len(x.types) == len(y.types) {
272 // Every type in x.types must be in y.types.
273 // Quadratic algorithm, but probably good enough for now.
274 // TODO(gri) we need a fast quick type ID/hash for all types.
276 for _, x := range x.types {
277 for _, y := range y.types {
279 continue L // x is in y.types
282 return false // x is not in y.types
291 // Two interface types are identical if they have the same set of methods with
292 // the same names and identical function types. Lower-case method names from
293 // different packages are always different. The order of the methods is irrelevant.
294 if y, ok := y.(*Interface); ok {
295 // If identical0 is called (indirectly) via an external API entry point
296 // (such as Identical, IdenticalIgnoreTags, etc.), check is nil. But in
297 // that case, interfaces are expected to be complete and lazy completion
298 // here is not needed.
300 check.completeInterface(nopos, x)
301 check.completeInterface(nopos, y)
305 if len(a) == len(b) {
306 // Interface types are the only types where cycles can occur
307 // that are not "terminated" via named types; and such cycles
308 // can only be created via method parameter types that are
309 // anonymous interfaces (directly or indirectly) embedding
310 // the current interface. Example:
312 // type T interface {
316 // If two such (differently named) interfaces are compared,
317 // endless recursion occurs if the cycle is not detected.
319 // If x and y were compared before, they must be equal
320 // (if they were not, the recursion would have stopped);
321 // search the ifacePair stack for the same pair.
323 // This is a quadratic algorithm, but in practice these stacks
324 // are extremely short (bounded by the nesting depth of interface
325 // type declarations that recur via parameter types, an extremely
326 // rare occurrence). An alternative implementation might use a
327 // "visited" map, but that is probably less efficient overall.
328 q := &ifacePair{x, y, p}
331 return true // same pair was compared before
336 assertSortedMethods(a)
337 assertSortedMethods(b)
339 for i, f := range a {
341 if f.Id() != g.Id() || !check.identical0(f.typ, g.typ, cmpTags, q) {
350 // Two map types are identical if they have identical key and value types.
351 if y, ok := y.(*Map); ok {
352 return check.identical0(x.key, y.key, cmpTags, p) && check.identical0(x.elem, y.elem, cmpTags, p)
356 // Two channel types are identical if they have identical value types
357 // and the same direction.
358 if y, ok := y.(*Chan); ok {
359 return x.dir == y.dir && check.identical0(x.elem, y.elem, cmpTags, p)
363 // Two named types are identical if their type names originate
364 // in the same type declaration.
365 if y, ok := y.(*Named); ok {
366 // TODO(gri) Why is x == y not sufficient? And if it is,
367 // we can just return false here because x == y
368 // is caught in the very beginning of this function.
369 return x.obj == y.obj
373 // nothing to do (x and y being equal is caught in the very beginning of this function)
376 // unreachable since types are expanded
379 // Either both types are theBottom, or both are theTop in which
380 // case the initial x == y check will have caught them. Otherwise
381 // they are not identical.
384 // avoid a crash in case of nil type
393 func (check *Checker) identicalTParams(x, y []*TypeName, cmpTags bool, p *ifacePair) bool {
394 if len(x) != len(y) {
397 for i, x := range x {
399 if !check.identical0(x.typ.(*TypeParam).bound, y.typ.(*TypeParam).bound, cmpTags, p) {
406 // Default returns the default "typed" type for an "untyped" type;
407 // it returns the incoming type for all other types. The default type
408 // for untyped nil is untyped nil.
410 func Default(typ Type) Type {
411 if t, ok := typ.(*Basic); ok {
418 return universeRune // use 'rune' name
422 return Typ[Complex128]