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(coreType(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(coreType(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 // isTypeLit reports whether t is a type literal.
68 // This includes all non-defined types, but also basic types.
69 // isTypeLit may be called with types that are not fully set up.
70 func isTypeLit(t Type) bool {
72 case *Named, *TypeParam:
78 // isTyped reports whether t is typed; i.e., not an untyped
79 // constant or boolean. isTyped may be called with types that
80 // are not fully set up.
81 func isTyped(t Type) bool {
82 // isTyped is called with types that are not fully
83 // set up. Must not call under()!
85 return b == nil || b.info&IsUntyped == 0
88 // isUntyped(t) is the same as !isTyped(t).
89 func isUntyped(t Type) bool {
93 // IsInterface reports whether t is an interface type.
94 func IsInterface(t Type) bool {
95 _, ok := under(t).(*Interface)
99 // isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
100 func isNonTypeParamInterface(t Type) bool {
101 return !isTypeParam(t) && IsInterface(t)
104 // isTypeParam reports whether t is a type parameter.
105 func isTypeParam(t Type) bool {
106 _, ok := t.(*TypeParam)
110 // hasEmptyTypeset reports whether t is a type parameter with an empty type set.
111 // The function does not force the computation of the type set and so is safe to
112 // use anywhere, but it may report a false negative if the type set has not been
114 func hasEmptyTypeset(t Type) bool {
115 if tpar, _ := t.(*TypeParam); tpar != nil && tpar.bound != nil {
116 iface, _ := safeUnderlying(tpar.bound).(*Interface)
117 return iface != nil && iface.tset != nil && iface.tset.IsEmpty()
122 // isGeneric reports whether a type is a generic, uninstantiated type
123 // (generic signatures are not included).
124 // TODO(gri) should we include signatures or assert that they are not present?
125 func isGeneric(t Type) bool {
126 // A parameterized type is only generic if it doesn't have an instantiation already.
127 named, _ := t.(*Named)
128 return named != nil && named.obj != nil && named.inst == nil && named.TypeParams().Len() > 0
131 // Comparable reports whether values of type T are comparable.
132 func Comparable(T Type) bool {
133 return comparable(T, true, nil, nil)
136 // If dynamic is set, non-type parameter interfaces are always comparable.
137 // If reportf != nil, it may be used to report why T is not comparable.
138 func comparable(T Type, dynamic bool, seen map[Type]bool, reportf func(string, ...interface{})) bool {
143 seen = make(map[Type]bool)
147 switch t := under(T).(type) {
149 // assume invalid types to be comparable
150 // to avoid follow-up errors
151 return t.kind != UntypedNil
152 case *Pointer, *Chan:
155 for _, f := range t.fields {
156 if !comparable(f.typ, dynamic, seen, nil) {
158 reportf("struct containing %s cannot be compared", f.typ)
165 if !comparable(t.elem, dynamic, seen, nil) {
167 reportf("%s cannot be compared", t)
173 if dynamic && !isTypeParam(T) || t.typeSet().IsComparable(seen) {
177 if t.typeSet().IsEmpty() {
178 reportf("empty type set")
180 reportf("incomparable types in type set")
188 // hasNil reports whether type t includes the nil value.
189 func hasNil(t Type) bool {
190 switch u := under(t).(type) {
192 return u.kind == UnsafePointer
193 case *Slice, *Pointer, *Signature, *Map, *Chan:
196 return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool {
197 return u != nil && hasNil(u)
203 // An ifacePair is a node in a stack of interface type pairs compared for identity.
204 type ifacePair struct {
209 func (p *ifacePair) identical(q *ifacePair) bool {
210 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x
213 // A comparer is used to compare types.
214 type comparer struct {
215 ignoreTags bool // if set, identical ignores struct tags
216 ignoreInvalids bool // if set, identical treats an invalid type as identical to any type
219 // For changes to this code the corresponding changes should be made to unifier.nify.
220 func (c *comparer) identical(x, y Type, p *ifacePair) bool {
225 if c.ignoreInvalids && (x == Typ[Invalid] || y == Typ[Invalid]) {
229 switch x := x.(type) {
231 // Basic types are singletons except for the rune and byte
232 // aliases, thus we cannot solely rely on the x == y check
233 // above. See also comment in TypeName.IsAlias.
234 if y, ok := y.(*Basic); ok {
235 return x.kind == y.kind
239 // Two array types are identical if they have identical element types
240 // and the same array length.
241 if y, ok := y.(*Array); ok {
242 // If one or both array lengths are unknown (< 0) due to some error,
243 // assume they are the same to avoid spurious follow-on errors.
244 return (x.len < 0 || y.len < 0 || x.len == y.len) && c.identical(x.elem, y.elem, p)
248 // Two slice types are identical if they have identical element types.
249 if y, ok := y.(*Slice); ok {
250 return c.identical(x.elem, y.elem, p)
254 // Two struct types are identical if they have the same sequence of fields,
255 // and if corresponding fields have the same names, and identical types,
256 // and identical tags. Two embedded fields are considered to have the same
257 // name. Lower-case field names from different packages are always different.
258 if y, ok := y.(*Struct); ok {
259 if x.NumFields() == y.NumFields() {
260 for i, f := range x.fields {
262 if f.embedded != g.embedded ||
263 !c.ignoreTags && x.Tag(i) != y.Tag(i) ||
264 !f.sameId(g.pkg, g.name) ||
265 !c.identical(f.typ, g.typ, p) {
274 // Two pointer types are identical if they have identical base types.
275 if y, ok := y.(*Pointer); ok {
276 return c.identical(x.base, y.base, p)
280 // Two tuples types are identical if they have the same number of elements
281 // and corresponding elements have identical types.
282 if y, ok := y.(*Tuple); ok {
283 if x.Len() == y.Len() {
285 for i, v := range x.vars {
287 if !c.identical(v.typ, w.typ, p) {
297 y, _ := y.(*Signature)
302 // Two function types are identical if they have the same number of
303 // parameters and result values, corresponding parameter and result types
304 // are identical, and either both functions are variadic or neither is.
305 // Parameter and result names are not required to match, and type
306 // parameters are considered identical modulo renaming.
308 if x.TypeParams().Len() != y.TypeParams().Len() {
312 // In the case of generic signatures, we will substitute in yparams and
315 yresults := y.results
317 if x.TypeParams().Len() > 0 {
318 // We must ignore type parameter names when comparing x and y. The
319 // easiest way to do this is to substitute x's type parameters for y's.
320 xtparams := x.TypeParams().list()
321 ytparams := y.TypeParams().list()
324 for i := range xtparams {
325 targs = append(targs, x.TypeParams().At(i))
327 smap := makeSubstMap(ytparams, targs)
329 var check *Checker // ok to call subst on a nil *Checker
330 ctxt := NewContext() // need a non-nil Context for the substitution below
332 // Constraints must be pair-wise identical, after substitution.
333 for i, xtparam := range xtparams {
334 ybound := check.subst(nopos, ytparams[i].bound, smap, nil, ctxt)
335 if !c.identical(xtparam.bound, ybound, p) {
340 yparams = check.subst(nopos, y.params, smap, nil, ctxt).(*Tuple)
341 yresults = check.subst(nopos, y.results, smap, nil, ctxt).(*Tuple)
344 return x.variadic == y.variadic &&
345 c.identical(x.params, yparams, p) &&
346 c.identical(x.results, yresults, p)
349 if y, _ := y.(*Union); y != nil {
350 // TODO(rfindley): can this be reached during type checking? If so,
351 // consider passing a type set map.
352 unionSets := make(map[*Union]*_TypeSet)
353 xset := computeUnionTypeSet(nil, unionSets, nopos, x)
354 yset := computeUnionTypeSet(nil, unionSets, nopos, y)
355 return xset.terms.equal(yset.terms)
359 // Two interface types are identical if they describe the same type sets.
360 // With the existing implementation restriction, this simplifies to:
362 // Two interface types are identical if they have the same set of methods with
363 // the same names and identical function types, and if any type restrictions
364 // are the same. Lower-case method names from different packages are always
365 // different. The order of the methods is irrelevant.
366 if y, ok := y.(*Interface); ok {
369 if xset.comparable != yset.comparable {
372 if !xset.terms.equal(yset.terms) {
377 if len(a) == len(b) {
378 // Interface types are the only types where cycles can occur
379 // that are not "terminated" via named types; and such cycles
380 // can only be created via method parameter types that are
381 // anonymous interfaces (directly or indirectly) embedding
382 // the current interface. Example:
384 // type T interface {
388 // If two such (differently named) interfaces are compared,
389 // endless recursion occurs if the cycle is not detected.
391 // If x and y were compared before, they must be equal
392 // (if they were not, the recursion would have stopped);
393 // search the ifacePair stack for the same pair.
395 // This is a quadratic algorithm, but in practice these stacks
396 // are extremely short (bounded by the nesting depth of interface
397 // type declarations that recur via parameter types, an extremely
398 // rare occurrence). An alternative implementation might use a
399 // "visited" map, but that is probably less efficient overall.
400 q := &ifacePair{x, y, p}
403 return true // same pair was compared before
408 assertSortedMethods(a)
409 assertSortedMethods(b)
411 for i, f := range a {
413 if f.Id() != g.Id() || !c.identical(f.typ, g.typ, q) {
422 // Two map types are identical if they have identical key and value types.
423 if y, ok := y.(*Map); ok {
424 return c.identical(x.key, y.key, p) && c.identical(x.elem, y.elem, p)
428 // Two channel types are identical if they have identical value types
429 // and the same direction.
430 if y, ok := y.(*Chan); ok {
431 return x.dir == y.dir && c.identical(x.elem, y.elem, p)
435 // Two named types are identical if their type names originate
436 // in the same type declaration; if they are instantiated they
437 // must have identical type argument lists.
438 if y, ok := y.(*Named); ok {
439 // check type arguments before origins to match unifier
440 // (for correct source code we need to do all checks so
441 // order doesn't matter)
442 xargs := x.TypeArgs().list()
443 yargs := y.TypeArgs().list()
444 if len(xargs) != len(yargs) {
447 for i, xarg := range xargs {
448 if !Identical(xarg, yargs[i]) {
452 return identicalOrigin(x, y)
456 // nothing to do (x and y being equal is caught in the very beginning of this function)
459 // avoid a crash in case of nil type
468 // identicalOrigin reports whether x and y originated in the same declaration.
469 func identicalOrigin(x, y *Named) bool {
470 // TODO(gri) is this correct?
471 return x.Origin().obj == y.Origin().obj
474 // identicalInstance reports if two type instantiations are identical.
475 // Instantiations are identical if their origin and type arguments are
477 func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool {
478 if len(xargs) != len(yargs) {
482 for i, xa := range xargs {
483 if !Identical(xa, yargs[i]) {
488 return Identical(xorig, yorig)
491 // Default returns the default "typed" type for an "untyped" type;
492 // it returns the incoming type for all other types. The default type
493 // for untyped nil is untyped nil.
494 func Default(t Type) Type {
495 if t, ok := t.(*Basic); ok {
502 return universeRune // use 'rune' name
506 return Typ[Complex128]
514 // maxType returns the "largest" type that encompasses both x and y.
515 // If x and y are different untyped numeric types, the result is the type of x or y
516 // that appears later in this list: integer, rune, floating-point, complex.
517 // Otherwise, if x != y, the result is nil.
518 func maxType(x, y Type) Type {
519 // We only care about untyped types (for now), so == is good enough.
520 // TODO(gri) investigate generalizing this function to simplify code elsewhere
524 if isUntyped(x) && isUntyped(y) && isNumeric(x) && isNumeric(y) {
525 // untyped types are basic types
526 if x.(*Basic).kind > y.(*Basic).kind {