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 // isValid reports whether t is a valid type.
10 func isValid(t Type) bool { return t != Typ[Invalid] }
12 // The isX predicates below report whether t is an X.
13 // If t is a type parameter the result is false; i.e.,
14 // these predicates don't look inside a type parameter.
16 func isBoolean(t Type) bool { return isBasic(t, IsBoolean) }
17 func isInteger(t Type) bool { return isBasic(t, IsInteger) }
18 func isUnsigned(t Type) bool { return isBasic(t, IsUnsigned) }
19 func isFloat(t Type) bool { return isBasic(t, IsFloat) }
20 func isComplex(t Type) bool { return isBasic(t, IsComplex) }
21 func isNumeric(t Type) bool { return isBasic(t, IsNumeric) }
22 func isString(t Type) bool { return isBasic(t, IsString) }
23 func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) }
24 func isConstType(t Type) bool { return isBasic(t, IsConstType) }
26 // isBasic reports whether under(t) is a basic type with the specified info.
27 // If t is a type parameter the result is false; i.e.,
28 // isBasic does not look inside a type parameter.
29 func isBasic(t Type, info BasicInfo) bool {
30 u, _ := under(t).(*Basic)
31 return u != nil && u.info&info != 0
34 // The allX predicates below report whether t is an X.
35 // If t is a type parameter the result is true if isX is true
36 // for all specified types of the type parameter's type set.
37 // allX is an optimized version of isX(coreType(t)) (which
38 // is the same as underIs(t, isX)).
40 func allBoolean(t Type) bool { return allBasic(t, IsBoolean) }
41 func allInteger(t Type) bool { return allBasic(t, IsInteger) }
42 func allUnsigned(t Type) bool { return allBasic(t, IsUnsigned) }
43 func allNumeric(t Type) bool { return allBasic(t, IsNumeric) }
44 func allString(t Type) bool { return allBasic(t, IsString) }
45 func allOrdered(t Type) bool { return allBasic(t, IsOrdered) }
46 func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) }
48 // allBasic reports whether under(t) is a basic type with the specified info.
49 // If t is a type parameter, the result is true if isBasic(t, info) is true
50 // for all specific types of the type parameter's type set.
51 // allBasic(t, info) is an optimized version of isBasic(coreType(t), info).
52 func allBasic(t Type, info BasicInfo) bool {
53 if tpar, _ := t.(*TypeParam); tpar != nil {
54 return tpar.is(func(t *term) bool { return t != nil && isBasic(t.typ, info) })
56 return isBasic(t, info)
59 // hasName reports whether t has a name. This includes
60 // predeclared types, defined types, and type parameters.
61 // hasName may be called with types that are not fully set up.
62 func hasName(t Type) bool {
64 case *Basic, *Named, *TypeParam:
70 // isTypeLit reports whether t is a type literal.
71 // This includes all non-defined types, but also basic types.
72 // isTypeLit may be called with types that are not fully set up.
73 func isTypeLit(t Type) bool {
75 case *Named, *TypeParam:
81 // isTyped reports whether t is typed; i.e., not an untyped
82 // constant or boolean. isTyped may be called with types that
83 // are not fully set up.
84 func isTyped(t Type) bool {
85 // isTyped is called with types that are not fully
86 // set up. Must not call under()!
88 return b == nil || b.info&IsUntyped == 0
91 // isUntyped(t) is the same as !isTyped(t).
92 func isUntyped(t Type) bool {
96 // IsInterface reports whether t is an interface type.
97 func IsInterface(t Type) bool {
98 _, ok := under(t).(*Interface)
102 // isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
103 func isNonTypeParamInterface(t Type) bool {
104 return !isTypeParam(t) && IsInterface(t)
107 // isTypeParam reports whether t is a type parameter.
108 func isTypeParam(t Type) bool {
109 _, ok := t.(*TypeParam)
113 // hasEmptyTypeset reports whether t is a type parameter with an empty type set.
114 // The function does not force the computation of the type set and so is safe to
115 // use anywhere, but it may report a false negative if the type set has not been
117 func hasEmptyTypeset(t Type) bool {
118 if tpar, _ := t.(*TypeParam); tpar != nil && tpar.bound != nil {
119 iface, _ := safeUnderlying(tpar.bound).(*Interface)
120 return iface != nil && iface.tset != nil && iface.tset.IsEmpty()
125 // isGeneric reports whether a type is a generic, uninstantiated type
126 // (generic signatures are not included).
127 // TODO(gri) should we include signatures or assert that they are not present?
128 func isGeneric(t Type) bool {
129 // A parameterized type is only generic if it doesn't have an instantiation already.
131 return named != nil && named.obj != nil && named.inst == nil && named.TypeParams().Len() > 0
134 // Comparable reports whether values of type T are comparable.
135 func Comparable(T Type) bool {
136 return comparable(T, true, nil, nil)
139 // If dynamic is set, non-type parameter interfaces are always comparable.
140 // If reportf != nil, it may be used to report why T is not comparable.
141 func comparable(T Type, dynamic bool, seen map[Type]bool, reportf func(string, ...interface{})) bool {
146 seen = make(map[Type]bool)
150 switch t := under(T).(type) {
152 // assume invalid types to be comparable
153 // to avoid follow-up errors
154 return t.kind != UntypedNil
155 case *Pointer, *Chan:
158 for _, f := range t.fields {
159 if !comparable(f.typ, dynamic, seen, nil) {
161 reportf("struct containing %s cannot be compared", f.typ)
168 if !comparable(t.elem, dynamic, seen, nil) {
170 reportf("%s cannot be compared", t)
176 if dynamic && !isTypeParam(T) || t.typeSet().IsComparable(seen) {
180 if t.typeSet().IsEmpty() {
181 reportf("empty type set")
183 reportf("incomparable types in type set")
191 // hasNil reports whether type t includes the nil value.
192 func hasNil(t Type) bool {
193 switch u := under(t).(type) {
195 return u.kind == UnsafePointer
196 case *Slice, *Pointer, *Signature, *Map, *Chan:
199 return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool {
200 return u != nil && hasNil(u)
206 // An ifacePair is a node in a stack of interface type pairs compared for identity.
207 type ifacePair struct {
212 func (p *ifacePair) identical(q *ifacePair) bool {
213 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
216 // A comparer is used to compare types.
217 type comparer struct {
218 ignoreTags bool // if set, identical ignores struct tags
219 ignoreInvalids bool // if set, identical treats an invalid type as identical to any type
222 // For changes to this code the corresponding changes should be made to unifier.nify.
223 func (c *comparer) identical(x, y Type, p *ifacePair) bool {
228 if c.ignoreInvalids && (!isValid(x) || !isValid(y)) {
232 switch x := x.(type) {
234 // Basic types are singletons except for the rune and byte
235 // aliases, thus we cannot solely rely on the x == y check
236 // above. See also comment in TypeName.IsAlias.
237 if y, ok := y.(*Basic); ok {
238 return x.kind == y.kind
242 // Two array types are identical if they have identical element types
243 // and the same array length.
244 if y, ok := y.(*Array); ok {
245 // If one or both array lengths are unknown (< 0) due to some error,
246 // assume they are the same to avoid spurious follow-on errors.
247 return (x.len < 0 || y.len < 0 || x.len == y.len) && c.identical(x.elem, y.elem, p)
251 // Two slice types are identical if they have identical element types.
252 if y, ok := y.(*Slice); ok {
253 return c.identical(x.elem, y.elem, p)
257 // Two struct types are identical if they have the same sequence of fields,
258 // and if corresponding fields have the same names, and identical types,
259 // and identical tags. Two embedded fields are considered to have the same
260 // name. Lower-case field names from different packages are always different.
261 if y, ok := y.(*Struct); ok {
262 if x.NumFields() == y.NumFields() {
263 for i, f := range x.fields {
265 if f.embedded != g.embedded ||
266 !c.ignoreTags && x.Tag(i) != y.Tag(i) ||
267 !f.sameId(g.pkg, g.name) ||
268 !c.identical(f.typ, g.typ, p) {
277 // Two pointer types are identical if they have identical base types.
278 if y, ok := y.(*Pointer); ok {
279 return c.identical(x.base, y.base, p)
283 // Two tuples types are identical if they have the same number of elements
284 // and corresponding elements have identical types.
285 if y, ok := y.(*Tuple); ok {
286 if x.Len() == y.Len() {
288 for i, v := range x.vars {
290 if !c.identical(v.typ, w.typ, p) {
300 y, _ := y.(*Signature)
305 // Two function types are identical if they have the same number of
306 // parameters and result values, corresponding parameter and result types
307 // are identical, and either both functions are variadic or neither is.
308 // Parameter and result names are not required to match, and type
309 // parameters are considered identical modulo renaming.
311 if x.TypeParams().Len() != y.TypeParams().Len() {
315 // In the case of generic signatures, we will substitute in yparams and
318 yresults := y.results
320 if x.TypeParams().Len() > 0 {
321 // We must ignore type parameter names when comparing x and y. The
322 // easiest way to do this is to substitute x's type parameters for y's.
323 xtparams := x.TypeParams().list()
324 ytparams := y.TypeParams().list()
327 for i := range xtparams {
328 targs = append(targs, x.TypeParams().At(i))
330 smap := makeSubstMap(ytparams, targs)
332 var check *Checker // ok to call subst on a nil *Checker
333 ctxt := NewContext() // need a non-nil Context for the substitution below
335 // Constraints must be pair-wise identical, after substitution.
336 for i, xtparam := range xtparams {
337 ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt)
338 if !c.identical(xtparam.bound, ybound, p) {
343 yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple)
344 yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple)
347 return x.variadic == y.variadic &&
348 c.identical(x.params, yparams, p) &&
349 c.identical(x.results, yresults, p)
352 if y, _ := y.(*Union); y != nil {
353 // TODO(rfindley): can this be reached during type checking? If so,
354 // consider passing a type set map.
355 unionSets := make(map[*Union]*_TypeSet)
356 xset := computeUnionTypeSet(nil, unionSets, nopos, x)
357 yset := computeUnionTypeSet(nil, unionSets, nopos, y)
358 return xset.terms.equal(yset.terms)
362 // Two interface types are identical if they describe the same type sets.
363 // With the existing implementation restriction, this simplifies to:
365 // Two interface types are identical if they have the same set of methods with
366 // the same names and identical function types, and if any type restrictions
367 // are the same. Lower-case method names from different packages are always
368 // different. The order of the methods is irrelevant.
369 if y, ok := y.(*Interface); ok {
372 if xset.comparable != yset.comparable {
375 if !xset.terms.equal(yset.terms) {
380 if len(a) == len(b) {
381 // Interface types are the only types where cycles can occur
382 // that are not "terminated" via named types; and such cycles
383 // can only be created via method parameter types that are
384 // anonymous interfaces (directly or indirectly) embedding
385 // the current interface. Example:
387 // type T interface {
391 // If two such (differently named) interfaces are compared,
392 // endless recursion occurs if the cycle is not detected.
394 // If x and y were compared before, they must be equal
395 // (if they were not, the recursion would have stopped);
396 // search the ifacePair stack for the same pair.
398 // This is a quadratic algorithm, but in practice these stacks
399 // are extremely short (bounded by the nesting depth of interface
400 // type declarations that recur via parameter types, an extremely
401 // rare occurrence). An alternative implementation might use a
402 // "visited" map, but that is probably less efficient overall.
403 q := &ifacePair{x, y, p}
406 return true // same pair was compared before
411 assertSortedMethods(a)
412 assertSortedMethods(b)
414 for i, f := range a {
416 if f.Id() != g.Id() || !c.identical(f.typ, g.typ, q) {
425 // Two map types are identical if they have identical key and value types.
426 if y, ok := y.(*Map); ok {
427 return c.identical(x.key, y.key, p) && c.identical(x.elem, y.elem, p)
431 // Two channel types are identical if they have identical value types
432 // and the same direction.
433 if y, ok := y.(*Chan); ok {
434 return x.dir == y.dir && c.identical(x.elem, y.elem, p)
438 // Two named types are identical if their type names originate
439 // in the same type declaration; if they are instantiated they
440 // must have identical type argument lists.
441 if y := asNamed(y); y != nil {
442 // check type arguments before origins to match unifier
443 // (for correct source code we need to do all checks so
444 // order doesn't matter)
445 xargs := x.TypeArgs().list()
446 yargs := y.TypeArgs().list()
447 if len(xargs) != len(yargs) {
450 for i, xarg := range xargs {
451 if !Identical(xarg, yargs[i]) {
455 return identicalOrigin(x, y)
459 // nothing to do (x and y being equal is caught in the very beginning of this function)
462 // avoid a crash in case of nil type
471 // identicalOrigin reports whether x and y originated in the same declaration.
472 func identicalOrigin(x, y *Named) bool {
473 // TODO(gri) is this correct?
474 return x.Origin().obj == y.Origin().obj
477 // identicalInstance reports if two type instantiations are identical.
478 // Instantiations are identical if their origin and type arguments are
480 func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool {
481 if len(xargs) != len(yargs) {
485 for i, xa := range xargs {
486 if !Identical(xa, yargs[i]) {
491 return Identical(xorig, yorig)
494 // Default returns the default "typed" type for an "untyped" type;
495 // it returns the incoming type for all other types. The default type
496 // for untyped nil is untyped nil.
497 func Default(t Type) Type {
498 if t, ok := t.(*Basic); ok {
505 return universeRune // use 'rune' name
509 return Typ[Complex128]
517 // maxType returns the "largest" type that encompasses both x and y.
518 // If x and y are different untyped numeric types, the result is the type of x or y
519 // that appears later in this list: integer, rune, floating-point, complex.
520 // Otherwise, if x != y, the result is nil.
521 func maxType(x, y Type) Type {
522 // We only care about untyped types (for now), so == is good enough.
523 // TODO(gri) investigate generalizing this function to simplify code elsewhere
527 if isUntyped(x) && isUntyped(y) && isNumeric(x) && isNumeric(y) {
528 // untyped types are basic types
529 if x.(*Basic).kind > y.(*Basic).kind {