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| 1 | namespace Syntax.Process is | |
| 2 | use Logging | |
| 3 | use Source.LOCATION | |
| 4 | ||
| 5 | use Semantic.Symbols.Function | |
| 6 | use Semantic.Symbols.FUNCTION_GROUP | |
| 7 | use Semantic.Symbols.Symbol | |
| 8 | use Semantic.Types.Type | |
| 9 | ||
| 10 | // The shape decided for a destructure of `from_type` into a | |
| 11 | // fixed list of target elements. Exactly one of `members` and | |
| 12 | // `deconstruct_function` is populated. | |
| 13 | // | |
| 14 | // `members` carries one entry per element (null where it could | |
| 15 | // not be resolved); the source for each element is loaded by | |
| 16 | // calling the corresponding symbol's `load`. | |
| 17 | // | |
| 18 | // `deconstruct_function` carries the resolved `deconstruct(...)` | |
| 19 | // instance method; the call shape is one INSTANCE call passing | |
| 20 | // ADDRESS args for each `ref` parameter, with the temps then | |
| 21 | // bound to the elements in order. | |
| 22 | // | |
| 23 | // Each constructor populates its own half, so `is_deconstruct` | |
| 24 | // says which one to read. | |
| 25 | @suppress("field-definite-assignment") | |
| 26 | class DESTRUCTURE_STRATEGY is | |
| 27 | // Per-element symbol; null entries mark slots that have no | |
| 28 | // resolvable member (the consumer logs an error and treats | |
| 29 | // the destructure as failed). | |
| 30 | members: Collections.List[Symbol?] public | |
| 31 | deconstruct_function: Function? public | |
| 32 | ||
| 33 | is_deconstruct: bool => deconstruct_function? | |
| 34 | ||
| 35 | init(members: Collections.List[Symbol?]) is | |
| 36 | super.init() | |
| 37 | self.members = members | |
| 38 | si | |
| 39 | ||
| 40 | init(deconstruct_function: Function) is | |
| 41 | super.init() | |
| 42 | self.deconstruct_function = deconstruct_function | |
| 43 | si | |
| 44 | si | |
| 45 | ||
| 46 | // Decides, for a destructure of a source of `from_type` into a | |
| 47 | // fixed list of target elements, how each element is supplied. | |
| 48 | // | |
| 49 | // Two entry points, matching the surface syntax split: | |
| 50 | // | |
| 51 | // - `resolve_strategy(from_type, element_count)` — positional | |
| 52 | // `(a, b) = source`. Tries in order: value-tuple positional; | |
| 53 | // `deconstruct(...)` instance method with all-`T ref` params; | |
| 54 | // conventionally-named positional members `` `0 ``, `` `1 ``, | |
| 55 | // ... A type without one of those shapes is not destructurable | |
| 56 | // positionally — there is no by-name fallback. | |
| 57 | // | |
| 58 | // - `resolve_strategy_by_name(from_type, field_names)` — named | |
| 59 | // `(local = field, …) = source`. Each element resolves to | |
| 60 | // `from_type.find_member(field_name)`. | |
| 61 | // | |
| 62 | // Pure and shared: COMPILE_EXPRESSIONS resolves here and logs an | |
| 63 | // error for any unresolved element; GENERATE_IL resolves the same | |
| 64 | // way but only ever runs for an already-valid destructure. | |
| 65 | // Keeping the decision in one place stops the two passes | |
| 66 | // drifting apart. | |
| 67 | class DESTRUCTURE_RESOLVER is | |
| 68 | // Resolve the destructure strategy and log an error against | |
| 69 | // `location` for any unresolvable case. When `field_names` is | |
| 70 | // null the destructure is positional and the failure is | |
| 71 | // reported as a count mismatch if the source has positional | |
| 72 | // members, otherwise as a not-destructurable source. When | |
| 73 | // `field_names` is non-null the destructure is by-name and | |
| 74 | // each missed name is reported individually. | |
| 75 | resolve_strategy_reporting( | |
| 76 | logger: Logger, | |
| 77 | location: LOCATION, | |
| 78 | from_type: Type?, | |
| 79 | element_count: int, | |
| 80 | field_names: Collections.List[string?]? | |
| 81 | ) -> DESTRUCTURE_STRATEGY static | |
| 82 | is | |
| 83 | let strategy = | |
| 84 | if field_names? then | |
| 85 | resolve_strategy_by_name(from_type, field_names) | |
| 86 | else | |
| 87 | resolve_strategy(from_type, element_count) | |
| 88 | fi | |
| 89 | ||
| 90 | if !from_type? \/ from_type.is_error then | |
| 91 | return strategy | |
| 92 | fi | |
| 93 | ||
| 94 | if strategy.is_deconstruct then | |
| 95 | return strategy | |
| 96 | fi | |
| 97 | ||
| 98 | let members = strategy.members | |
| 99 | let resolved mut = 0 | |
| 100 | ||
| 101 | for member in members do | |
| 102 | if member? then | |
| 103 | resolved = resolved + 1 | |
| 104 | fi | |
| 105 | od | |
| 106 | ||
| 107 | if resolved == element_count then | |
| 108 | return strategy | |
| 109 | fi | |
| 110 | ||
| 111 | if field_names? then | |
| 112 | // Named-group failure: pinpoint the missed field | |
| 113 | // names individually. | |
| 114 | for i in 0..field_names.count do | |
| 115 | if !members[i]? then | |
| 116 | let name = field_names[i] | |
| 117 | ||
| 118 | logger.error(location, "{from_type} has no member {name}") | |
| 119 | fi | |
| 120 | od | |
| 121 | ||
| 122 | return strategy | |
| 123 | fi | |
| 124 | ||
| 125 | let positional_arity = | |
| 126 | if from_type.is_value_tuple then | |
| 127 | from_type.arguments.count | |
| 128 | else | |
| 129 | positional_member_count(from_type) | |
| 130 | fi | |
| 131 | ||
| 132 | if positional_arity > 0 then | |
| 133 | logger.error(location, "expected {element_count} destructuring elements but found {positional_arity}") | |
| 134 | else | |
| 135 | logger.error(location, "cannot destructure {from_type}") | |
| 136 | fi | |
| 137 | ||
| 138 | return strategy | |
| 139 | si | |
| 140 | ||
| 141 | resolve_strategy( | |
| 142 | from_type: Type?, | |
| 143 | element_count: int | |
| 144 | ) -> DESTRUCTURE_STRATEGY static is | |
| 145 | if !from_type? \/ from_type.is_error then | |
| 146 | return DESTRUCTURE_STRATEGY(_nulls(element_count)) | |
| 147 | fi | |
| 148 | ||
| 149 | if | |
| 150 | from_type.is_value_tuple /\ | |
| 151 | from_type.arguments.count == element_count | |
| 152 | then | |
| 153 | return DESTRUCTURE_STRATEGY(_positional_members(from_type, element_count)) | |
| 154 | fi | |
| 155 | ||
| 156 | let deconstruct = try_resolve_deconstruct(from_type, element_count) | |
| 157 | ||
| 158 | if deconstruct? then | |
| 159 | return DESTRUCTURE_STRATEGY(deconstruct) | |
| 160 | fi | |
| 161 | ||
| 162 | let pos_arity = positional_member_count(from_type) | |
| 163 | ||
| 164 | if pos_arity > 0 /\ pos_arity == element_count then | |
| 165 | return DESTRUCTURE_STRATEGY(_positional_members(from_type, element_count)) | |
| 166 | fi | |
| 167 | ||
| 168 | return DESTRUCTURE_STRATEGY(_nulls(element_count)) | |
| 169 | si | |
| 170 | ||
| 171 | // `field_names` carries one entry per element naming the | |
| 172 | // source member that backs that element; a null entry marks | |
| 173 | // a nested destructuring group (which holds its own | |
| 174 | // resolver state). A null member result on a non-null name | |
| 175 | // means the source has no such member — the caller reports | |
| 176 | // the diagnostic. | |
| 177 | resolve_strategy_by_name( | |
| 178 | from_type: Type?, | |
| 179 | field_names: Collections.List[string?] | |
| 180 | ) -> DESTRUCTURE_STRATEGY static is | |
| 181 | if !from_type? \/ from_type.is_error then | |
| 182 | return DESTRUCTURE_STRATEGY(_nulls(field_names.count)) | |
| 183 | fi | |
| 184 | ||
| 185 | let result = Collections.LIST[Symbol?]() | |
| 186 | for name in field_names do | |
| 187 | if !name? then | |
| 188 | result.add(null) | |
| 189 | else | |
| 190 | result.add(from_type.find_member(name)) | |
| 191 | fi | |
| 192 | od | |
| 193 | return DESTRUCTURE_STRATEGY(result) | |
| 194 | si | |
| 195 | ||
| 196 | _nulls(count: int) -> Collections.List[Symbol?] static is | |
| 197 | let result = Collections.LIST[Symbol?]() | |
| 198 | for i in 0..count do | |
| 199 | result.add(null) | |
| 200 | od | |
| 201 | return result | |
| 202 | si | |
| 203 | ||
| 204 | // The number of leading `0 `1 ... conventionally-named | |
| 205 | // destructure members the type exposes. | |
| 206 | positional_member_count(type: Type) -> int static is | |
| 207 | let count mut = 0 | |
| 208 | let member mut = type.find_destructure_member(count) | |
| 209 | ||
| 210 | while member? do | |
| 211 | count = count + 1 | |
| 212 | member = type.find_destructure_member(count) | |
| 213 | od | |
| 214 | ||
| 215 | return count | |
| 216 | si | |
| 217 | ||
| 218 | // Returns the resolved `deconstruct(...)` instance method | |
| 219 | // whose arity equals `element_count` and whose parameters | |
| 220 | // are all `T ref`, or null if no such method exists. When | |
| 221 | // more than one overload matches the arity, returns null — | |
| 222 | // the caller falls through to the next destructure strategy. | |
| 223 | try_resolve_deconstruct( | |
| 224 | from_type: Type?, | |
| 225 | element_count: int | |
| 226 | ) -> Function? static is | |
| 227 | if !from_type? then | |
| 228 | return null | |
| 229 | fi | |
| 230 | ||
| 231 | let member = from_type.find_member("deconstruct") | |
| 232 | ||
| 233 | if !member? then | |
| 234 | return null | |
| 235 | fi | |
| 236 | ||
| 237 | let candidates = Collections.LIST[Function]() | |
| 238 | ||
| 239 | if let group: FUNCTION_GROUP = member then | |
| 240 | for f in group.functions do | |
| 241 | if is_viable_deconstruct(f, element_count) then | |
| 242 | candidates.add(f) | |
| 243 | fi | |
| 244 | od | |
| 245 | elif let function: Function = member then | |
| 246 | if is_viable_deconstruct(function, element_count) then | |
| 247 | candidates.add(function) | |
| 248 | fi | |
| 249 | fi | |
| 250 | ||
| 251 | if candidates.count == 1 then | |
| 252 | return candidates[0] | |
| 253 | fi | |
| 254 | ||
| 255 | return null | |
| 256 | si | |
| 257 | ||
| 258 | is_viable_deconstruct(f: Function?, element_count: int) -> bool static is | |
| 259 | if !f? \/ !f.is_instance then | |
| 260 | return false | |
| 261 | fi | |
| 262 | ||
| 263 | if !f.are_arguments_declared \/ f.arguments.count != element_count then | |
| 264 | return false | |
| 265 | fi | |
| 266 | ||
| 267 | for a in f.arguments do | |
| 268 | if !a.is_ref then | |
| 269 | return false | |
| 270 | fi | |
| 271 | od | |
| 272 | ||
| 273 | return true | |
| 274 | si | |
| 275 | ||
| 276 | _positional_members(from_type: Type, element_count: int) -> Collections.List[Symbol?] static is | |
| 277 | let result = Collections.LIST[Symbol?]() | |
| 278 | for i in 0..element_count do | |
| 279 | result.add(from_type.find_destructure_member(i)) | |
| 280 | od | |
| 281 | return result | |
| 282 | si | |
| 283 | si | |
| 284 | si |