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when assigning parameter to function, the returned typevar substitutions must take into account any typevar recomputations

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Joeri Exelmans 2025-05-18 09:58:11 +02:00
parent 8266e59b94
commit 248d8ddef1
2 changed files with 25 additions and 9 deletions
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18
lib/generics/generics.js
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@ -68,10 +68,12 @@ export const mergeTwoWay = (m1, m2) => {
checkConflict(m1, m2);
// checkConflict(m2, m1); // <- don't think this is necessary...
// actually merge
let stable = false;
while (!stable) {
let remaining = 2;
while (remaining > 0) {
// notice we swap m2 and m1, so the rewriting can happen both ways:
let stable;
[stable, m2, m1] = mergeOneWay(m1, m2);
remaining -= stable;
}
const result = new Map([...m1, ...m2]);
// console.log("mergeTwoWay result =", result);
@ -187,8 +189,7 @@ export const substitute = (type, substitutions, stack=[]) => {
};
export const assignFn = (funType, paramType) => {
const [outType] = assignFnSubstitutions(funType, paramType);
return outType;
return assignFnSubstitutions(funType, paramType)[2];
};
// same as above, but also returns the substitutions that took place
@ -197,12 +198,13 @@ export const assignFnSubstitutions = (funType, paramType) => {
throw new NotAFunctionError(`${prettyT(funType)} is not a function type!`);
}
const [[refunType, funS], [reparamType, paramS]] = recomputeTypeVarsSubstitutions([funType, paramType]);
const recomputationSubstitutions = mergeTwoWay(funS, paramS);
const [inType, outType] = refunType.params.map(p => p(refunType));
const {substitutions} = __unify(inType, reparamType);
// console.log(substitutions, prettyT(outType));
const {type: newInType, substitutions} = __unify(inType, reparamType);
const inTypeSubst = mergeTwoWay(substitutions, recomputationSubstitutions);
const substitutedFnType = substitute(outType, substitutions);
const computedOutType = recomputeTypeVars([substitutedFnType])[0];
return [computedOutType, substitutions];
const [computedOutType, outSubst] = recomputeTypeVarsSubstitutions([substitutedFnType])[0];
return [newInType, inTypeSubst, computedOutType, outSubst];
};
// Ensures that no type variables overlap