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| 1 | namespace Syntax.Process is | |
| 2 | use Semantic.Types.Type | |
| 3 | ||
| 4 | // Whether `a =~ b` gets its null checks written around the call. | |
| 5 | // | |
| 6 | // Each decline leaves the operands resolving exactly as they did | |
| 7 | // before, so getting one wrong is a silent change of meaning rather | |
| 8 | // than a compile failure: the call still builds and still answers, | |
| 9 | // just from the wrong place. | |
| 10 | class NULL_SAFE_EQUALITY_GATE is | |
| 11 | // The operands have to include something absent to test. Which | |
| 12 | // optional lowering each one uses does not matter here: the | |
| 13 | // presence test and the payload are built per operand, so a | |
| 14 | // reference optional and a `NULLABLE[T]` or `MAYBE[T]` reach | |
| 15 | // the same shape. | |
| 16 | accepts_operands(left_type: Type?, right_type: Type?) -> bool static is | |
| 17 | if !left_type? \/ !right_type? then | |
| 18 | return false | |
| 19 | fi | |
| 20 | ||
| 21 | if left_type.is_error \/ right_type.is_error then | |
| 22 | return false | |
| 23 | fi | |
| 24 | ||
| 25 | return left_type.is_optional \/ right_type.is_optional | |
| 26 | si | |
| 27 | ||
| 28 | // The operator has to be one the lowering can call at all: | |
| 29 | // reached with the left operand as its receiver, and taking | |
| 30 | // one parameter. An enum's `=~` qualifies although it reports | |
| 31 | // itself as neither static nor an instance member - it is an | |
| 32 | // innate method, and its call takes a receiver like any other. | |
| 33 | // One hidden from operator resolution is not what the | |
| 34 | // expression calls in the first place, so it is left alone | |
| 35 | // entirely. | |
| 36 | // | |
| 37 | // It also has to answer bool. Nothing requires `=~` to, the way | |
| 38 | // `<>` is required to answer int, and the null arms have no | |
| 39 | // sensible value to produce for an operator that answers | |
| 40 | // something else - so rather than reinterpret its result, leave | |
| 41 | // the comparison to resolve as it did. | |
| 42 | accepts_operator(function: Semantic.Symbols.Function?, bool_type: Type?) -> bool static is | |
| 43 | if !function? \/ !bool_type? then | |
| 44 | return false | |
| 45 | fi | |
| 46 | ||
| 47 | if | |
| 48 | !(function.is_instance \/ isa Semantic.Symbols.INNATE_METHOD(function)) \/ | |
| 49 | function.is_hidden_from_operator_resolution | |
| 50 | then | |
| 51 | return false | |
| 52 | fi | |
| 53 | ||
| 54 | if function.arguments.count != 1 then | |
| 55 | return false | |
| 56 | fi | |
| 57 | ||
| 58 | let return_type = function.return_type | |
| 59 | ||
| 60 | return return_type? /\ return_type.matches(bool_type) | |
| 61 | si | |
| 62 | ||
| 63 | // A global operator taking both operands as arguments, for the | |
| 64 | // types the operands hold once presence is settled. Both | |
| 65 | // parameters have to be non-optional: one that declares an | |
| 66 | // optional parameter means to decide for an absent operand | |
| 67 | // itself, and this lowering never hands it one, so it is left | |
| 68 | // to resolve as written instead. | |
| 69 | accepts_global_operator(function: Semantic.Symbols.Function?, bool_type: Type?) -> bool static is | |
| 70 | if !function? \/ !bool_type? then | |
| 71 | return false | |
| 72 | fi | |
| 73 | ||
| 74 | if function.is_instance \/ function.is_hidden_from_operator_resolution then | |
| 75 | return false | |
| 76 | fi | |
| 77 | ||
| 78 | if function.arguments.count != 2 then | |
| 79 | return false | |
| 80 | fi | |
| 81 | ||
| 82 | if function.arguments[0].is_optional \/ function.arguments[1].is_optional then | |
| 83 | return false | |
| 84 | fi | |
| 85 | ||
| 86 | let return_type = function.return_type | |
| 87 | ||
| 88 | return return_type? /\ return_type.matches(bool_type) | |
| 89 | si | |
| 90 | ||
| 91 | // Whether the absent *argument* is answered here rather than by | |
| 92 | // the operator. An operator declaring that parameter optional | |
| 93 | // is written to answer for one itself, so it is handed the | |
| 94 | // value and decides. | |
| 95 | // | |
| 96 | // The right operand is the operator's only parameter when it | |
| 97 | // takes the left as a receiver, and its second when it takes | |
| 98 | // both as arguments. | |
| 99 | // | |
| 100 | // The absent *receiver* is never its decision: there is nothing | |
| 101 | // to dispatch on, so that arm is always answered here. | |
| 102 | guards_argument(function: Semantic.Symbols.Function?) -> bool static is | |
| 103 | if !function? \/ function.arguments.count < 1 \/ function.arguments.count > 2 then | |
| 104 | return false | |
| 105 | fi | |
| 106 | ||
| 107 | let argument = function.arguments[function.arguments.count - 1] | |
| 108 | ||
| 109 | return !argument.is_optional | |
| 110 | si | |
| 111 | si | |
| 112 | si |