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const {
convertZListToItemArray,
findIdentity,
isZFunctionCall,
isZReference,
isZType
} = require( './utils.js' );
/**
* Determine whether comparand type-compares to comparator.
*
* Type-comparison adheres to the following rules. Type A (comparand) type-compares
* as type B (comparator) iff
* - the identity of type B is Z1, OR
* - the identity of type A is identical to that of type B, OR
* - type A and type B are both Z4s, AND
* - for every key in type A, the key's type type-compares as the corresponding
* key in type B
*
* For the moment, type-comparison just doesn't touch generic types. If either
* comparand or comparator is a function call, compareTypes returns true.
*
* @param {Object} comparand type A, as defined above
* @param {Object} comparator type B, as defined above
* @return {boolean} whether comparand type-compares as comparator
*/
function compareTypes( comparand, comparator ) {
const comparandIdentity = findIdentity( comparand );
const comparatorIdentity = findIdentity( comparator );
if ( isZFunctionCall( comparandIdentity ) ) {
return true;
}
if ( isZFunctionCall( comparatorIdentity ) ) {
return true;
}
if ( isZReference( comparatorIdentity ) ) {
// Case 1: comparatorIdentity is Z1.
if ( comparatorIdentity.Z9K1 === 'Z1' ) {
return true;
}
// Case 2: identities are both references to built-in types.
if ( isZReference( comparandIdentity ) ) {
return comparandIdentity.Z9K1 === comparatorIdentity.Z9K1;
}
}
// If we reach this point, it means that the two types are user-defined
// (and not generic for now; see function docstring). In this case, we
// define type-comparison via a sort of duck-typing. If type A's keys stand
// in a 1:1 relationship with type B's such that each key in type A
// type-compares to the corresponding key in type B, then we say that the
// two types type-compare.
if ( isZType( comparator ) && isZType( comparand ) ) {
const comparandKeys = convertZListToItemArray( comparand.Z4K2 );
const comparatorKeys = convertZListToItemArray( comparator.Z4K2 );
if ( comparatorKeys.length !== comparandKeys.length ) {
return false;
}
for ( const index in comparatorKeys ) {
const comparatorKey = comparatorKeys[ index ];
const comparandKey = comparandKeys[ index ];
if ( !compareTypes( comparandKey.Z3K1, comparatorKey.Z3K1 ) ) {
return false;
}
}
return true;
}
return false;
}
module.exports = { compareTypes };
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