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 types 8 9import "sort" 10 11func isNamed(typ Type) bool { 12 if _, ok := typ.(*Basic); ok { 13 return ok 14 } 15 _, ok := typ.(*Named) 16 return ok 17} 18 19func isBoolean(typ Type) bool { 20 t, ok := typ.Underlying().(*Basic) 21 return ok && t.info&IsBoolean != 0 22} 23 24func isInteger(typ Type) bool { 25 t, ok := typ.Underlying().(*Basic) 26 return ok && t.info&IsInteger != 0 27} 28 29func isUnsigned(typ Type) bool { 30 t, ok := typ.Underlying().(*Basic) 31 return ok && t.info&IsUnsigned != 0 32} 33 34func isFloat(typ Type) bool { 35 t, ok := typ.Underlying().(*Basic) 36 return ok && t.info&IsFloat != 0 37} 38 39func isComplex(typ Type) bool { 40 t, ok := typ.Underlying().(*Basic) 41 return ok && t.info&IsComplex != 0 42} 43 44func isNumeric(typ Type) bool { 45 t, ok := typ.Underlying().(*Basic) 46 return ok && t.info&IsNumeric != 0 47} 48 49func isString(typ Type) bool { 50 t, ok := typ.Underlying().(*Basic) 51 return ok && t.info&IsString != 0 52} 53 54func isTyped(typ Type) bool { 55 t, ok := typ.Underlying().(*Basic) 56 return !ok || t.info&IsUntyped == 0 57} 58 59func isUntyped(typ Type) bool { 60 t, ok := typ.Underlying().(*Basic) 61 return ok && t.info&IsUntyped != 0 62} 63 64func isOrdered(typ Type) bool { 65 t, ok := typ.Underlying().(*Basic) 66 return ok && t.info&IsOrdered != 0 67} 68 69func isConstType(typ Type) bool { 70 t, ok := typ.Underlying().(*Basic) 71 return ok && t.info&IsConstType != 0 72} 73 74// IsInterface reports whether typ is an interface type. 75func IsInterface(typ Type) bool { 76 _, ok := typ.Underlying().(*Interface) 77 return ok 78} 79 80// Comparable reports whether values of type T are comparable. 81func Comparable(T Type) bool { 82 switch t := T.Underlying().(type) { 83 case *Basic: 84 // assume invalid types to be comparable 85 // to avoid follow-up errors 86 return t.kind != UntypedNil 87 case *Pointer, *Interface, *Chan: 88 return true 89 case *Struct: 90 for _, f := range t.fields { 91 if !Comparable(f.typ) { 92 return false 93 } 94 } 95 return true 96 case *Array: 97 return Comparable(t.elem) 98 } 99 return false 100} 101 102// hasNil reports whether a type includes the nil value. 103func hasNil(typ Type) bool { 104 switch t := typ.Underlying().(type) { 105 case *Basic: 106 return t.kind == UnsafePointer 107 case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan: 108 return true 109 } 110 return false 111} 112 113// Identical reports whether x and y are identical types. 114// Receivers of Signature types are ignored. 115func Identical(x, y Type) bool { 116 return identical(x, y, true, nil) 117} 118 119// IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored. 120// Receivers of Signature types are ignored. 121func IdenticalIgnoreTags(x, y Type) bool { 122 return identical(x, y, false, nil) 123} 124 125// An ifacePair is a node in a stack of interface type pairs compared for identity. 126type ifacePair struct { 127 x, y *Interface 128 prev *ifacePair 129} 130 131func (p *ifacePair) identical(q *ifacePair) bool { 132 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x 133} 134 135func identical(x, y Type, cmpTags bool, p *ifacePair) bool { 136 if x == y { 137 return true 138 } 139 140 switch x := x.(type) { 141 case *Basic: 142 // Basic types are singletons except for the rune and byte 143 // aliases, thus we cannot solely rely on the x == y check 144 // above. See also comment in TypeName.IsAlias. 145 if y, ok := y.(*Basic); ok { 146 return x.kind == y.kind 147 } 148 149 case *Array: 150 // Two array types are identical if they have identical element types 151 // and the same array length. 152 if y, ok := y.(*Array); ok { 153 // If one or both array lengths are unknown (< 0) due to some error, 154 // assume they are the same to avoid spurious follow-on errors. 155 return (x.len < 0 || y.len < 0 || x.len == y.len) && identical(x.elem, y.elem, cmpTags, p) 156 } 157 158 case *Slice: 159 // Two slice types are identical if they have identical element types. 160 if y, ok := y.(*Slice); ok { 161 return identical(x.elem, y.elem, cmpTags, p) 162 } 163 164 case *Struct: 165 // Two struct types are identical if they have the same sequence of fields, 166 // and if corresponding fields have the same names, and identical types, 167 // and identical tags. Two embedded fields are considered to have the same 168 // name. Lower-case field names from different packages are always different. 169 if y, ok := y.(*Struct); ok { 170 if x.NumFields() == y.NumFields() { 171 for i, f := range x.fields { 172 g := y.fields[i] 173 if f.embedded != g.embedded || 174 cmpTags && x.Tag(i) != y.Tag(i) || 175 !f.sameId(g.pkg, g.name) || 176 !identical(f.typ, g.typ, cmpTags, p) { 177 return false 178 } 179 } 180 return true 181 } 182 } 183 184 case *Pointer: 185 // Two pointer types are identical if they have identical base types. 186 if y, ok := y.(*Pointer); ok { 187 return identical(x.base, y.base, cmpTags, p) 188 } 189 190 case *Tuple: 191 // Two tuples types are identical if they have the same number of elements 192 // and corresponding elements have identical types. 193 if y, ok := y.(*Tuple); ok { 194 if x.Len() == y.Len() { 195 if x != nil { 196 for i, v := range x.vars { 197 w := y.vars[i] 198 if !identical(v.typ, w.typ, cmpTags, p) { 199 return false 200 } 201 } 202 } 203 return true 204 } 205 } 206 207 case *Signature: 208 // Two function types are identical if they have the same number of parameters 209 // and result values, corresponding parameter and result types are identical, 210 // and either both functions are variadic or neither is. Parameter and result 211 // names are not required to match. 212 if y, ok := y.(*Signature); ok { 213 return x.variadic == y.variadic && 214 identical(x.params, y.params, cmpTags, p) && 215 identical(x.results, y.results, cmpTags, p) 216 } 217 218 case *Interface: 219 // Two interface types are identical if they have the same set of methods with 220 // the same names and identical function types. Lower-case method names from 221 // different packages are always different. The order of the methods is irrelevant. 222 if y, ok := y.(*Interface); ok { 223 a := x.allMethods 224 b := y.allMethods 225 if len(a) == len(b) { 226 // Interface types are the only types where cycles can occur 227 // that are not "terminated" via named types; and such cycles 228 // can only be created via method parameter types that are 229 // anonymous interfaces (directly or indirectly) embedding 230 // the current interface. Example: 231 // 232 // type T interface { 233 // m() interface{T} 234 // } 235 // 236 // If two such (differently named) interfaces are compared, 237 // endless recursion occurs if the cycle is not detected. 238 // 239 // If x and y were compared before, they must be equal 240 // (if they were not, the recursion would have stopped); 241 // search the ifacePair stack for the same pair. 242 // 243 // This is a quadratic algorithm, but in practice these stacks 244 // are extremely short (bounded by the nesting depth of interface 245 // type declarations that recur via parameter types, an extremely 246 // rare occurrence). An alternative implementation might use a 247 // "visited" map, but that is probably less efficient overall. 248 q := &ifacePair{x, y, p} 249 for p != nil { 250 if p.identical(q) { 251 return true // same pair was compared before 252 } 253 p = p.prev 254 } 255 if debug { 256 assert(sort.IsSorted(byUniqueMethodName(a))) 257 assert(sort.IsSorted(byUniqueMethodName(b))) 258 } 259 for i, f := range a { 260 g := b[i] 261 if f.Id() != g.Id() || !identical(f.typ, g.typ, cmpTags, q) { 262 return false 263 } 264 } 265 return true 266 } 267 } 268 269 case *Map: 270 // Two map types are identical if they have identical key and value types. 271 if y, ok := y.(*Map); ok { 272 return identical(x.key, y.key, cmpTags, p) && identical(x.elem, y.elem, cmpTags, p) 273 } 274 275 case *Chan: 276 // Two channel types are identical if they have identical value types 277 // and the same direction. 278 if y, ok := y.(*Chan); ok { 279 return x.dir == y.dir && identical(x.elem, y.elem, cmpTags, p) 280 } 281 282 case *Named: 283 // Two named types are identical if their type names originate 284 // in the same type declaration. 285 if y, ok := y.(*Named); ok { 286 return x.obj == y.obj 287 } 288 289 case nil: 290 291 default: 292 unreachable() 293 } 294 295 return false 296} 297 298// Default returns the default "typed" type for an "untyped" type; 299// it returns the incoming type for all other types. The default type 300// for untyped nil is untyped nil. 301// 302func Default(typ Type) Type { 303 if t, ok := typ.(*Basic); ok { 304 switch t.kind { 305 case UntypedBool: 306 return Typ[Bool] 307 case UntypedInt: 308 return Typ[Int] 309 case UntypedRune: 310 return universeRune // use 'rune' name 311 case UntypedFloat: 312 return Typ[Float64] 313 case UntypedComplex: 314 return Typ[Complex128] 315 case UntypedString: 316 return Typ[String] 317 } 318 } 319 return typ 320} 321