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. 4 5// This file implements commonly used type predicates. 6 7package types2 8 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. 12 13func isBoolean(t Type) bool { return isBasic(t, IsBoolean) } 14func isInteger(t Type) bool { return isBasic(t, IsInteger) } 15func isUnsigned(t Type) bool { return isBasic(t, IsUnsigned) } 16func isFloat(t Type) bool { return isBasic(t, IsFloat) } 17func isComplex(t Type) bool { return isBasic(t, IsComplex) } 18func isNumeric(t Type) bool { return isBasic(t, IsNumeric) } 19func isString(t Type) bool { return isBasic(t, IsString) } 20func isIntegerOrFloat(t Type) bool { return isBasic(t, IsInteger|IsFloat) } 21func isConstType(t Type) bool { return isBasic(t, IsConstType) } 22 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. 26func isBasic(t Type, info BasicInfo) bool { 27 u, _ := under(t).(*Basic) 28 return u != nil && u.info&info != 0 29} 30 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)). 36 37func allBoolean(t Type) bool { return allBasic(t, IsBoolean) } 38func allInteger(t Type) bool { return allBasic(t, IsInteger) } 39func allUnsigned(t Type) bool { return allBasic(t, IsUnsigned) } 40func allNumeric(t Type) bool { return allBasic(t, IsNumeric) } 41func allString(t Type) bool { return allBasic(t, IsString) } 42func allOrdered(t Type) bool { return allBasic(t, IsOrdered) } 43func allNumericOrString(t Type) bool { return allBasic(t, IsNumeric|IsString) } 44 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). 49func 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) }) 52 } 53 return isBasic(t, info) 54} 55 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. 59func hasName(t Type) bool { 60 switch t.(type) { 61 case *Basic, *Named, *TypeParam: 62 return true 63 } 64 return false 65} 66 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. 70func isTyped(t Type) bool { 71 // isTyped is called with types that are not fully 72 // set up. Must not call under()! 73 b, _ := t.(*Basic) 74 return b == nil || b.info&IsUntyped == 0 75} 76 77// isUntyped(t) is the same as !isTyped(t). 78func isUntyped(t Type) bool { 79 return !isTyped(t) 80} 81 82// IsInterface reports whether t is an interface type. 83func IsInterface(t Type) bool { 84 _, ok := under(t).(*Interface) 85 return ok 86} 87 88// isTypeParam reports whether t is a type parameter. 89func isTypeParam(t Type) bool { 90 _, ok := t.(*TypeParam) 91 return ok 92} 93 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? 97func 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 101} 102 103// Comparable reports whether values of type T are comparable. 104func Comparable(T Type) bool { 105 return comparable(T, nil) 106} 107 108func comparable(T Type, seen map[Type]bool) bool { 109 if seen[T] { 110 return true 111 } 112 if seen == nil { 113 seen = make(map[Type]bool) 114 } 115 seen[T] = true 116 117 switch t := under(T).(type) { 118 case *Basic: 119 // assume invalid types to be comparable 120 // to avoid follow-up errors 121 return t.kind != UntypedNil 122 case *Pointer, *Chan: 123 return true 124 case *Struct: 125 for _, f := range t.fields { 126 if !comparable(f.typ, seen) { 127 return false 128 } 129 } 130 return true 131 case *Array: 132 return comparable(t.elem, seen) 133 case *Interface: 134 return !isTypeParam(T) || t.IsComparable() 135 } 136 return false 137} 138 139// hasNil reports whether type t includes the nil value. 140func hasNil(t Type) bool { 141 switch u := under(t).(type) { 142 case *Basic: 143 return u.kind == UnsafePointer 144 case *Slice, *Pointer, *Signature, *Map, *Chan: 145 return true 146 case *Interface: 147 return !isTypeParam(t) || u.typeSet().underIs(func(u Type) bool { 148 return u != nil && hasNil(u) 149 }) 150 } 151 return false 152} 153 154// An ifacePair is a node in a stack of interface type pairs compared for identity. 155type ifacePair struct { 156 x, y *Interface 157 prev *ifacePair 158} 159 160func (p *ifacePair) identical(q *ifacePair) bool { 161 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x 162} 163 164// For changes to this code the corresponding changes should be made to unifier.nify. 165func identical(x, y Type, cmpTags bool, p *ifacePair) bool { 166 if x == y { 167 return true 168 } 169 170 switch x := x.(type) { 171 case *Basic: 172 // Basic types are singletons except for the rune and byte 173 // aliases, thus we cannot solely rely on the x == y check 174 // above. See also comment in TypeName.IsAlias. 175 if y, ok := y.(*Basic); ok { 176 return x.kind == y.kind 177 } 178 179 case *Array: 180 // Two array types are identical if they have identical element types 181 // and the same array length. 182 if y, ok := y.(*Array); ok { 183 // If one or both array lengths are unknown (< 0) due to some error, 184 // assume they are the same to avoid spurious follow-on errors. 185 return (x.len < 0 || y.len < 0 || x.len == y.len) && identical(x.elem, y.elem, cmpTags, p) 186 } 187 188 case *Slice: 189 // Two slice types are identical if they have identical element types. 190 if y, ok := y.(*Slice); ok { 191 return identical(x.elem, y.elem, cmpTags, p) 192 } 193 194 case *Struct: 195 // Two struct types are identical if they have the same sequence of fields, 196 // and if corresponding fields have the same names, and identical types, 197 // and identical tags. Two embedded fields are considered to have the same 198 // name. Lower-case field names from different packages are always different. 199 if y, ok := y.(*Struct); ok { 200 if x.NumFields() == y.NumFields() { 201 for i, f := range x.fields { 202 g := y.fields[i] 203 if f.embedded != g.embedded || 204 cmpTags && x.Tag(i) != y.Tag(i) || 205 !f.sameId(g.pkg, g.name) || 206 !identical(f.typ, g.typ, cmpTags, p) { 207 return false 208 } 209 } 210 return true 211 } 212 } 213 214 case *Pointer: 215 // Two pointer types are identical if they have identical base types. 216 if y, ok := y.(*Pointer); ok { 217 return identical(x.base, y.base, cmpTags, p) 218 } 219 220 case *Tuple: 221 // Two tuples types are identical if they have the same number of elements 222 // and corresponding elements have identical types. 223 if y, ok := y.(*Tuple); ok { 224 if x.Len() == y.Len() { 225 if x != nil { 226 for i, v := range x.vars { 227 w := y.vars[i] 228 if !identical(v.typ, w.typ, cmpTags, p) { 229 return false 230 } 231 } 232 } 233 return true 234 } 235 } 236 237 case *Signature: 238 y, _ := y.(*Signature) 239 if y == nil { 240 return false 241 } 242 243 // Two function types are identical if they have the same number of 244 // parameters and result values, corresponding parameter and result types 245 // are identical, and either both functions are variadic or neither is. 246 // Parameter and result names are not required to match, and type 247 // parameters are considered identical modulo renaming. 248 249 if x.TypeParams().Len() != y.TypeParams().Len() { 250 return false 251 } 252 253 // In the case of generic signatures, we will substitute in yparams and 254 // yresults. 255 yparams := y.params 256 yresults := y.results 257 258 if x.TypeParams().Len() > 0 { 259 // We must ignore type parameter names when comparing x and y. The 260 // easiest way to do this is to substitute x's type parameters for y's. 261 xtparams := x.TypeParams().list() 262 ytparams := y.TypeParams().list() 263 264 var targs []Type 265 for i := range xtparams { 266 targs = append(targs, x.TypeParams().At(i)) 267 } 268 smap := makeSubstMap(ytparams, targs) 269 270 var check *Checker // ok to call subst on a nil *Checker 271 272 // Constraints must be pair-wise identical, after substitution. 273 for i, xtparam := range xtparams { 274 ybound := check.subst(nopos, ytparams[i].bound, smap, nil) 275 if !identical(xtparam.bound, ybound, cmpTags, p) { 276 return false 277 } 278 } 279 280 yparams = check.subst(nopos, y.params, smap, nil).(*Tuple) 281 yresults = check.subst(nopos, y.results, smap, nil).(*Tuple) 282 } 283 284 return x.variadic == y.variadic && 285 identical(x.params, yparams, cmpTags, p) && 286 identical(x.results, yresults, cmpTags, p) 287 288 case *Union: 289 if y, _ := y.(*Union); y != nil { 290 xset := computeUnionTypeSet(nil, nopos, x) 291 yset := computeUnionTypeSet(nil, nopos, y) 292 return xset.terms.equal(yset.terms) 293 } 294 295 case *Interface: 296 // Two interface types are identical if they describe the same type sets. 297 // With the existing implementation restriction, this simplifies to: 298 // 299 // Two interface types are identical if they have the same set of methods with 300 // the same names and identical function types, and if any type restrictions 301 // are the same. Lower-case method names from different packages are always 302 // different. The order of the methods is irrelevant. 303 if y, ok := y.(*Interface); ok { 304 xset := x.typeSet() 305 yset := y.typeSet() 306 if !xset.terms.equal(yset.terms) { 307 return false 308 } 309 a := xset.methods 310 b := yset.methods 311 if len(a) == len(b) { 312 // Interface types are the only types where cycles can occur 313 // that are not "terminated" via named types; and such cycles 314 // can only be created via method parameter types that are 315 // anonymous interfaces (directly or indirectly) embedding 316 // the current interface. Example: 317 // 318 // type T interface { 319 // m() interface{T} 320 // } 321 // 322 // If two such (differently named) interfaces are compared, 323 // endless recursion occurs if the cycle is not detected. 324 // 325 // If x and y were compared before, they must be equal 326 // (if they were not, the recursion would have stopped); 327 // search the ifacePair stack for the same pair. 328 // 329 // This is a quadratic algorithm, but in practice these stacks 330 // are extremely short (bounded by the nesting depth of interface 331 // type declarations that recur via parameter types, an extremely 332 // rare occurrence). An alternative implementation might use a 333 // "visited" map, but that is probably less efficient overall. 334 q := &ifacePair{x, y, p} 335 for p != nil { 336 if p.identical(q) { 337 return true // same pair was compared before 338 } 339 p = p.prev 340 } 341 if debug { 342 assertSortedMethods(a) 343 assertSortedMethods(b) 344 } 345 for i, f := range a { 346 g := b[i] 347 if f.Id() != g.Id() || !identical(f.typ, g.typ, cmpTags, q) { 348 return false 349 } 350 } 351 return true 352 } 353 } 354 355 case *Map: 356 // Two map types are identical if they have identical key and value types. 357 if y, ok := y.(*Map); ok { 358 return identical(x.key, y.key, cmpTags, p) && identical(x.elem, y.elem, cmpTags, p) 359 } 360 361 case *Chan: 362 // Two channel types are identical if they have identical value types 363 // and the same direction. 364 if y, ok := y.(*Chan); ok { 365 return x.dir == y.dir && identical(x.elem, y.elem, cmpTags, p) 366 } 367 368 case *Named: 369 // Two named types are identical if their type names originate 370 // in the same type declaration. 371 if y, ok := y.(*Named); ok { 372 xargs := x.TypeArgs().list() 373 yargs := y.TypeArgs().list() 374 375 if len(xargs) != len(yargs) { 376 return false 377 } 378 379 if len(xargs) > 0 { 380 // Instances are identical if their original type and type arguments 381 // are identical. 382 if !Identical(x.orig, y.orig) { 383 return false 384 } 385 for i, xa := range xargs { 386 if !Identical(xa, yargs[i]) { 387 return false 388 } 389 } 390 return true 391 } 392 393 // TODO(gri) Why is x == y not sufficient? And if it is, 394 // we can just return false here because x == y 395 // is caught in the very beginning of this function. 396 return x.obj == y.obj 397 } 398 399 case *TypeParam: 400 // nothing to do (x and y being equal is caught in the very beginning of this function) 401 402 case nil: 403 // avoid a crash in case of nil type 404 405 default: 406 unreachable() 407 } 408 409 return false 410} 411 412// identicalInstance reports if two type instantiations are identical. 413// Instantiations are identical if their origin and type arguments are 414// identical. 415func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool { 416 if len(xargs) != len(yargs) { 417 return false 418 } 419 420 for i, xa := range xargs { 421 if !Identical(xa, yargs[i]) { 422 return false 423 } 424 } 425 426 return Identical(xorig, yorig) 427} 428 429// Default returns the default "typed" type for an "untyped" type; 430// it returns the incoming type for all other types. The default type 431// for untyped nil is untyped nil. 432func Default(t Type) Type { 433 if t, ok := t.(*Basic); ok { 434 switch t.kind { 435 case UntypedBool: 436 return Typ[Bool] 437 case UntypedInt: 438 return Typ[Int] 439 case UntypedRune: 440 return universeRune // use 'rune' name 441 case UntypedFloat: 442 return Typ[Float64] 443 case UntypedComplex: 444 return Typ[Complex128] 445 case UntypedString: 446 return Typ[String] 447 } 448 } 449 return t 450} 451