microsoft/TypeScript
1
0
Fork 0
mirror of https://github.com/microsoft/TypeScript.git synced 2026-06-13 22:00:59 -05:00
Code Issues Packages Projects Releases 212 Wiki Activity

Propagate variance reliability (#62604)

Browse Source
This commit is contained in:
Anders Hejlsberg
2025-10-31 11:51:01 -07:00
committed by GitHub
parent 9222837872
commit cc05d940a2
5 changed files with 141 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

48
src/compiler/checker.ts
View File

@@ -23190,29 +23190,35 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// the `-?` modifier in a mapped type (where, no matter how the inputs are related, the outputs still might not be)
related = relation === identityRelation ? isRelatedTo(s, t, RecursionFlags.Both, /*reportErrors*/ false) : compareTypesIdentical(s, t);
}
else if (variance === VarianceFlags.Covariant) {
related = isRelatedTo(s, t, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
else if (variance === VarianceFlags.Contravariant) {
related = isRelatedTo(t, s, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
else if (variance === VarianceFlags.Bivariant) {
// In the bivariant case we first compare contravariantly without reporting
// errors. Then, if that doesn't succeed, we compare covariantly with error
// reporting. Thus, error elaboration will be based on the the covariant check,
// which is generally easier to reason about.
related = isRelatedTo(t, s, RecursionFlags.Both, /*reportErrors*/ false);
if (!related) {
else {
// Propagate unreliable variance flag
if (inVarianceComputation && varianceFlags & VarianceFlags.Unreliable) {
instantiateType(s, reportUnreliableMapper);
}
if (variance === VarianceFlags.Covariant) {
related = isRelatedTo(s, t, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
}
else {
// In the invariant case we first compare covariantly, and only when that
// succeeds do we proceed to compare contravariantly. Thus, error elaboration
// will typically be based on the covariant check.
related = isRelatedTo(s, t, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
if (related) {
related &= isRelatedTo(t, s, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
else if (variance === VarianceFlags.Contravariant) {
related = isRelatedTo(t, s, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
else if (variance === VarianceFlags.Bivariant) {
// In the bivariant case we first compare contravariantly without reporting
// errors. Then, if that doesn't succeed, we compare covariantly with error
// reporting. Thus, error elaboration will be based on the the covariant check,
// which is generally easier to reason about.
related = isRelatedTo(t, s, RecursionFlags.Both, /*reportErrors*/ false);
if (!related) {
related = isRelatedTo(s, t, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
}
else {
// In the invariant case we first compare covariantly, and only when that
// succeeds do we proceed to compare contravariantly. Thus, error elaboration
// will typically be based on the covariant check.
related = isRelatedTo(s, t, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
if (related) {
related &= isRelatedTo(t, s, RecursionFlags.Both, reportErrors, /*headMessage*/ undefined, intersectionState);
}
}
}
if (!related) {