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 // The isX predicates below report whether t is an X.
10 // If t is a type parameter the result is false; i.e.,
11 // these predicates don't look inside a type parameter.
13 func isBoolean(t Type) bool { return isBasic(t, IsBoolean) }
14 func isInteger(t Type) bool { return isBasic(t, IsInteger) }
15 func isUnsigned(t Type) bool { return isBasic(t, IsUnsigned) }
16 func isFloat(t Type) bool { return isBasic(t, IsFloat) }
17 func isComplex(t Type) bool { return isBasic(t, IsComplex) }
18 func isNumeric(t Type) bool { return isBasic(t, IsNumeric) }
19 func isString(t Type) bool { return isBasic(t, IsString) }
20 func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) }
21 func isConstType(t Type) bool { return isBasic(t, IsConstType) }
23 // isBasic reports whether under(t) is a basic type with the specified info.
24 // If t is a type parameter the result is false; i.e.,
25 // isBasic does not look inside a type parameter.
26 func isBasic(t Type, info BasicInfo) bool {
27 u, _ := under(t).(*Basic)
28 return u != nil && u.info&info != 0
31 // The allX predicates below report whether t is an X.
32 // If t is a type parameter the result is true if isX is true
33 // for all specified types of the type parameter's type set.
34 // allX is an optimized version of isX(structuralType(t)) (which
35 // is the same as underIs(t, isX)).
37 func allBoolean(t Type) bool { return allBasic(t, IsBoolean) }
38 func allInteger(t Type) bool { return allBasic(t, IsInteger) }
39 func allUnsigned(t Type) bool { return allBasic(t, IsUnsigned) }
40 func allNumeric(t Type) bool { return allBasic(t, IsNumeric) }
41 func allString(t Type) bool { return allBasic(t, IsString) }
42 func allOrdered(t Type) bool { return allBasic(t, IsOrdered) }
43 func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) }
45 // allBasic reports whether under(t) is a basic type with the specified info.
46 // If t is a type parameter, the result is true if isBasic(t, info) is true
47 // for all specific types of the type parameter's type set.
48 // allBasic(t, info) is an optimized version of isBasic(structuralType(t), info).
49 func allBasic(t Type, info BasicInfo) bool {
50 if tpar, _ := t.(*TypeParam); tpar != nil {
51 return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) })
53 return isBasic(t, info)
56 // hasName reports whether t has a name. This includes
57 // predeclared types, defined types, and type parameters.
58 // hasName may be called with types that are not fully set up.
59 func hasName(t Type) bool {
61 case *Basic, *Named, *TypeParam:
67 // isTyped reports whether t is typed; i.e., not an untyped
68 // constant or boolean. isTyped may be called with types that
69 // are not fully set up.
70 func isTyped(t Type) bool {
71 // isTyped is called with types that are not fully
72 // set up. Must not call under()!
74 return b == nil || b.info&IsUntyped == 0
77 // isUntyped(t) is the same as !isTyped(t).
78 func isUntyped(t Type) bool {
82 // IsInterface reports whether t is an interface type.
83 func IsInterface(t Type) bool {
84 _, ok := under(t).(*Interface)
88 // isTypeParam reports whether t is a type parameter.
89 func isTypeParam(t Type) bool {
90 _, ok := t.(*TypeParam)
94 // isGeneric reports whether a type is a generic, uninstantiated type
95 // (generic signatures are not included).
96 // TODO(gri) should we include signatures or assert that they are not present?
97 func isGeneric(t Type) bool {
98 // A parameterized type is only generic if it doesn't have an instantiation already.
99 named, _ := t.(*Named)
100 return named != nil && named.obj != nil && named.targs == nil && named.TypeParams() != nil
103 // Comparable reports whether values of type T are comparable.
104 func Comparable(T Type) bool {
105 return comparable(T, nil, nil)
108 // If reportf != nil, it may be used to report why T is not comparable.
109 func comparable(T Type, seen map[Type]bool, reportf func(string, ...interface{})) bool {
114 seen = make(map[Type]bool)
118 switch t := under(T).(type) {
120 // assume invalid types to be comparable
121 // to avoid follow-up errors
122 return t.kind != UntypedNil
123 case *Pointer, *Chan:
126 for _, f := range t.fields {
127 if !comparable(f.typ, seen, nil) {
129 reportf("struct containing %s cannot be compared", f.typ)
136 if !comparable(t.elem, seen, nil) {
138 reportf("%s cannot be compared", t)
144 return !isTypeParam(T) || t.typeSet().IsComparable(seen)
149 // hasNil reports whether type t includes the nil value.
150 func hasNil(t Type) bool {
151 switch u := under(t).(type) {
153 return u.kind == UnsafePointer
154 case *Slice, *Pointer, *Signature, *Map, *Chan:
157 return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool {
158 return u != nil && hasNil(u)
164 // An ifacePair is a node in a stack of interface type pairs compared for identity.
165 type ifacePair struct {
170 func (p *ifacePair) identical(q *ifacePair) bool {
171 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
174 // For changes to this code the corresponding changes should be made to unifier.nify.
175 func identical(x, y Type, cmpTags bool, p *ifacePair) bool {
180 switch x := x.(type) {
182 // Basic types are singletons except for the rune and byte
183 // aliases, thus we cannot solely rely on the x == y check
184 // above. See also comment in TypeName.IsAlias.
185 if y, ok := y.(*Basic); ok {
186 return x.kind == y.kind
190 // Two array types are identical if they have identical element types
191 // and the same array length.
192 if y, ok := y.(*Array); ok {
193 // If one or both array lengths are unknown (< 0) due to some error,
194 // assume they are the same to avoid spurious follow-on errors.
195 return (x.len < 0 || y.len < 0 || x.len == y.len) && identical(x.elem, y.elem, cmpTags, p)
199 // Two slice types are identical if they have identical element types.
200 if y, ok := y.(*Slice); ok {
201 return identical(x.elem, y.elem, cmpTags, p)
205 // Two struct types are identical if they have the same sequence of fields,
206 // and if corresponding fields have the same names, and identical types,
207 // and identical tags. Two embedded fields are considered to have the same
208 // name. Lower-case field names from different packages are always different.
209 if y, ok := y.(*Struct); ok {
210 if x.NumFields() == y.NumFields() {
211 for i, f := range x.fields {
213 if f.embedded != g.embedded ||
214 cmpTags && x.Tag(i) != y.Tag(i) ||
215 !f.sameId(g.pkg, g.name) ||
216 !identical(f.typ, g.typ, cmpTags, p) {
225 // Two pointer types are identical if they have identical base types.
226 if y, ok := y.(*Pointer); ok {
227 return identical(x.base, y.base, cmpTags, p)
231 // Two tuples types are identical if they have the same number of elements
232 // and corresponding elements have identical types.
233 if y, ok := y.(*Tuple); ok {
234 if x.Len() == y.Len() {
236 for i, v := range x.vars {
238 if !identical(v.typ, w.typ, cmpTags, p) {
248 y, _ := y.(*Signature)
253 // Two function types are identical if they have the same number of
254 // parameters and result values, corresponding parameter and result types
255 // are identical, and either both functions are variadic or neither is.
256 // Parameter and result names are not required to match, and type
257 // parameters are considered identical modulo renaming.
259 if x.TypeParams().Len() != y.TypeParams().Len() {
263 // In the case of generic signatures, we will substitute in yparams and
266 yresults := y.results
268 if x.TypeParams().Len() > 0 {
269 // We must ignore type parameter names when comparing x and y. The
270 // easiest way to do this is to substitute x's type parameters for y's.
271 xtparams := x.TypeParams().list()
272 ytparams := y.TypeParams().list()
275 for i := range xtparams {
276 targs = append(targs, x.TypeParams().At(i))
278 smap := makeSubstMap(ytparams, targs)
280 var check *Checker // ok to call subst on a nil *Checker
282 // Constraints must be pair-wise identical, after substitution.
283 for i, xtparam := range xtparams {
284 ybound := check.subst(nopos, ytparams[i].bound, smap, nil)
285 if !identical(xtparam.bound, ybound, cmpTags, p) {
290 yparams = check.subst(nopos, y.params, smap, nil).(*Tuple)
291 yresults = check.subst(nopos, y.results, smap, nil).(*Tuple)
294 return x.variadic == y.variadic &&
295 identical(x.params, yparams, cmpTags, p) &&
296 identical(x.results, yresults, cmpTags, p)
299 if y, _ := y.(*Union); y != nil {
300 // TODO(rfindley): can this be reached during type checking? If so,
301 // consider passing a type set map.
302 unionSets := make(map[*Union]*_TypeSet)
303 xset := computeUnionTypeSet(nil, unionSets, nopos, x)
304 yset := computeUnionTypeSet(nil, unionSets, nopos, y)
305 return xset.terms.equal(yset.terms)
309 // Two interface types are identical if they describe the same type sets.
310 // With the existing implementation restriction, this simplifies to:
312 // Two interface types are identical if they have the same set of methods with
313 // the same names and identical function types, and if any type restrictions
314 // are the same. Lower-case method names from different packages are always
315 // different. The order of the methods is irrelevant.
316 if y, ok := y.(*Interface); ok {
319 if xset.comparable != yset.comparable {
322 if !xset.terms.equal(yset.terms) {
327 if len(a) == len(b) {
328 // Interface types are the only types where cycles can occur
329 // that are not "terminated" via named types; and such cycles
330 // can only be created via method parameter types that are
331 // anonymous interfaces (directly or indirectly) embedding
332 // the current interface. Example:
334 // type T interface {
338 // If two such (differently named) interfaces are compared,
339 // endless recursion occurs if the cycle is not detected.
341 // If x and y were compared before, they must be equal
342 // (if they were not, the recursion would have stopped);
343 // search the ifacePair stack for the same pair.
345 // This is a quadratic algorithm, but in practice these stacks
346 // are extremely short (bounded by the nesting depth of interface
347 // type declarations that recur via parameter types, an extremely
348 // rare occurrence). An alternative implementation might use a
349 // "visited" map, but that is probably less efficient overall.
350 q := &ifacePair{x, y, p}
353 return true // same pair was compared before
358 assertSortedMethods(a)
359 assertSortedMethods(b)
361 for i, f := range a {
363 if f.Id() != g.Id() || !identical(f.typ, g.typ, cmpTags, q) {
372 // Two map types are identical if they have identical key and value types.
373 if y, ok := y.(*Map); ok {
374 return identical(x.key, y.key, cmpTags, p) && identical(x.elem, y.elem, cmpTags, p)
378 // Two channel types are identical if they have identical value types
379 // and the same direction.
380 if y, ok := y.(*Chan); ok {
381 return x.dir == y.dir && identical(x.elem, y.elem, cmpTags, p)
385 // Two named types are identical if their type names originate
386 // in the same type declaration.
387 if y, ok := y.(*Named); ok {
388 xargs := x.TypeArgs().list()
389 yargs := y.TypeArgs().list()
391 if len(xargs) != len(yargs) {
396 // Instances are identical if their original type and type arguments
398 if !Identical(x.orig, y.orig) {
401 for i, xa := range xargs {
402 if !Identical(xa, yargs[i]) {
409 // TODO(gri) Why is x == y not sufficient? And if it is,
410 // we can just return false here because x == y
411 // is caught in the very beginning of this function.
412 return x.obj == y.obj
416 // nothing to do (x and y being equal is caught in the very beginning of this function)
419 // avoid a crash in case of nil type
428 // identicalInstance reports if two type instantiations are identical.
429 // Instantiations are identical if their origin and type arguments are
431 func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool {
432 if len(xargs) != len(yargs) {
436 for i, xa := range xargs {
437 if !Identical(xa, yargs[i]) {
442 return Identical(xorig, yorig)
445 // Default returns the default "typed" type for an "untyped" type;
446 // it returns the incoming type for all other types. The default type
447 // for untyped nil is untyped nil.
448 func Default(t Type) Type {
449 if t, ok := t.(*Basic); ok {
456 return universeRune // use 'rune' name
460 return Typ[Complex128]