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 return comparable(T, nil) 83} 84 85func comparable(T Type, seen map[Type]bool) bool { 86 if seen[T] { 87 return true 88 } 89 if seen == nil { 90 seen = make(map[Type]bool) 91 } 92 seen[T] = true 93 94 switch t := T.Underlying().(type) { 95 case *Basic: 96 // assume invalid types to be comparable 97 // to avoid follow-up errors 98 return t.kind != UntypedNil 99 case *Pointer, *Interface, *Chan: 100 return true 101 case *Struct: 102 for _, f := range t.fields { 103 if !comparable(f.typ, seen) { 104 return false 105 } 106 } 107 return true 108 case *Array: 109 return comparable(t.elem, seen) 110 } 111 return false 112} 113 114// hasNil reports whether a type includes the nil value. 115func hasNil(typ Type) bool { 116 switch t := typ.Underlying().(type) { 117 case *Basic: 118 return t.kind == UnsafePointer 119 case *Slice, *Pointer, *Signature, *Interface, *Map, *Chan: 120 return true 121 } 122 return false 123} 124 125// identical reports whether x and y are identical types. 126// Receivers of Signature types are ignored. 127func (check *Checker) identical(x, y Type) bool { 128 return check.identical0(x, y, true, nil) 129} 130 131// identicalIgnoreTags reports whether x and y are identical types if tags are ignored. 132// Receivers of Signature types are ignored. 133func (check *Checker) identicalIgnoreTags(x, y Type) bool { 134 return check.identical0(x, y, false, nil) 135} 136 137// An ifacePair is a node in a stack of interface type pairs compared for identity. 138type ifacePair struct { 139 x, y *Interface 140 prev *ifacePair 141} 142 143func (p *ifacePair) identical(q *ifacePair) bool { 144 return p.x == q.x && p.y == q.y || p.x == q.y && p.y == q.x 145} 146 147func (check *Checker) identical0(x, y Type, cmpTags bool, p *ifacePair) bool { 148 if x == y { 149 return true 150 } 151 152 switch x := x.(type) { 153 case *Basic: 154 // Basic types are singletons except for the rune and byte 155 // aliases, thus we cannot solely rely on the x == y check 156 // above. See also comment in TypeName.IsAlias. 157 if y, ok := y.(*Basic); ok { 158 return x.kind == y.kind 159 } 160 161 case *Array: 162 // Two array types are identical if they have identical element types 163 // and the same array length. 164 if y, ok := y.(*Array); ok { 165 // If one or both array lengths are unknown (< 0) due to some error, 166 // assume they are the same to avoid spurious follow-on errors. 167 return (x.len < 0 || y.len < 0 || x.len == y.len) && check.identical0(x.elem, y.elem, cmpTags, p) 168 } 169 170 case *Slice: 171 // Two slice types are identical if they have identical element types. 172 if y, ok := y.(*Slice); ok { 173 return check.identical0(x.elem, y.elem, cmpTags, p) 174 } 175 176 case *Struct: 177 // Two struct types are identical if they have the same sequence of fields, 178 // and if corresponding fields have the same names, and identical types, 179 // and identical tags. Two embedded fields are considered to have the same 180 // name. Lower-case field names from different packages are always different. 181 if y, ok := y.(*Struct); ok { 182 if x.NumFields() == y.NumFields() { 183 for i, f := range x.fields { 184 g := y.fields[i] 185 if f.embedded != g.embedded || 186 cmpTags && x.Tag(i) != y.Tag(i) || 187 !f.sameId(g.pkg, g.name) || 188 !check.identical0(f.typ, g.typ, cmpTags, p) { 189 return false 190 } 191 } 192 return true 193 } 194 } 195 196 case *Pointer: 197 // Two pointer types are identical if they have identical base types. 198 if y, ok := y.(*Pointer); ok { 199 return check.identical0(x.base, y.base, cmpTags, p) 200 } 201 202 case *Tuple: 203 // Two tuples types are identical if they have the same number of elements 204 // and corresponding elements have identical types. 205 if y, ok := y.(*Tuple); ok { 206 if x.Len() == y.Len() { 207 if x != nil { 208 for i, v := range x.vars { 209 w := y.vars[i] 210 if !check.identical0(v.typ, w.typ, cmpTags, p) { 211 return false 212 } 213 } 214 } 215 return true 216 } 217 } 218 219 case *Signature: 220 // Two function types are identical if they have the same number of parameters 221 // and result values, corresponding parameter and result types are identical, 222 // and either both functions are variadic or neither is. Parameter and result 223 // names are not required to match. 224 if y, ok := y.(*Signature); ok { 225 return x.variadic == y.variadic && 226 check.identical0(x.params, y.params, cmpTags, p) && 227 check.identical0(x.results, y.results, cmpTags, p) 228 } 229 230 case *Interface: 231 // Two interface types are identical if they have the same set of methods with 232 // the same names and identical function types. Lower-case method names from 233 // different packages are always different. The order of the methods is irrelevant. 234 if y, ok := y.(*Interface); ok { 235 // If identical0 is called (indirectly) via an external API entry point 236 // (such as Identical, IdenticalIgnoreTags, etc.), check is nil. But in 237 // that case, interfaces are expected to be complete and lazy completion 238 // here is not needed. 239 if check != nil { 240 check.completeInterface(x) 241 check.completeInterface(y) 242 } 243 a := x.allMethods 244 b := y.allMethods 245 if len(a) == len(b) { 246 // Interface types are the only types where cycles can occur 247 // that are not "terminated" via named types; and such cycles 248 // can only be created via method parameter types that are 249 // anonymous interfaces (directly or indirectly) embedding 250 // the current interface. Example: 251 // 252 // type T interface { 253 // m() interface{T} 254 // } 255 // 256 // If two such (differently named) interfaces are compared, 257 // endless recursion occurs if the cycle is not detected. 258 // 259 // If x and y were compared before, they must be equal 260 // (if they were not, the recursion would have stopped); 261 // search the ifacePair stack for the same pair. 262 // 263 // This is a quadratic algorithm, but in practice these stacks 264 // are extremely short (bounded by the nesting depth of interface 265 // type declarations that recur via parameter types, an extremely 266 // rare occurrence). An alternative implementation might use a 267 // "visited" map, but that is probably less efficient overall. 268 q := &ifacePair{x, y, p} 269 for p != nil { 270 if p.identical(q) { 271 return true // same pair was compared before 272 } 273 p = p.prev 274 } 275 if debug { 276 assert(sort.IsSorted(byUniqueMethodName(a))) 277 assert(sort.IsSorted(byUniqueMethodName(b))) 278 } 279 for i, f := range a { 280 g := b[i] 281 if f.Id() != g.Id() || !check.identical0(f.typ, g.typ, cmpTags, q) { 282 return false 283 } 284 } 285 return true 286 } 287 } 288 289 case *Map: 290 // Two map types are identical if they have identical key and value types. 291 if y, ok := y.(*Map); ok { 292 return check.identical0(x.key, y.key, cmpTags, p) && check.identical0(x.elem, y.elem, cmpTags, p) 293 } 294 295 case *Chan: 296 // Two channel types are identical if they have identical value types 297 // and the same direction. 298 if y, ok := y.(*Chan); ok { 299 return x.dir == y.dir && check.identical0(x.elem, y.elem, cmpTags, p) 300 } 301 302 case *Named: 303 // Two named types are identical if their type names originate 304 // in the same type declaration. 305 if y, ok := y.(*Named); ok { 306 return x.obj == y.obj 307 } 308 309 case nil: 310 311 default: 312 unreachable() 313 } 314 315 return false 316} 317 318// Default returns the default "typed" type for an "untyped" type; 319// it returns the incoming type for all other types. The default type 320// for untyped nil is untyped nil. 321// 322func Default(typ Type) Type { 323 if t, ok := typ.(*Basic); ok { 324 switch t.kind { 325 case UntypedBool: 326 return Typ[Bool] 327 case UntypedInt: 328 return Typ[Int] 329 case UntypedRune: 330 return universeRune // use 'rune' name 331 case UntypedFloat: 332 return Typ[Float64] 333 case UntypedComplex: 334 return Typ[Complex128] 335 case UntypedString: 336 return Typ[String] 337 } 338 } 339 return typ 340} 341