Skip to content

check intersection props for never-reduction in a stable order #64521

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
Anders Hejlsberg (ahejlsberg) merged 1 commit into from
Sep 29, 2026
+4 −3
Merged

check intersection props for never-reduction in a stable order #64521

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 4 additions & 3 deletions tsc/internal/checker/checker.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -22215,14 +22215,15 @@ func (c *Checker) isMappingOfSameObjectType(types []*Type) bool {

func (c *Checker) somePropertyReducesToNever(t *Type) bool {
// Collect declaration counts for each property across all constituent types of the intersection.
counts := make(map[string]int)
var counts collections.OrderedMap[string, int]
for _, t := range t.Types() {
for _, prop := range c.getPropertiesOfType(t) {
counts[prop.Name]++
counts.Set(prop.Name, counts.GetOrZero(prop.Name)+1)
}
}
// Check if any property appears in more than one constituent type and reduces to 'never'.
for propName, count := range counts {
// Go in the order the properties were found so the combined properties are created in the same order every time.
for propName, count := range counts.Entries() {
if count > 1 {
if prop := c.getPropertyOfUnionOrIntersectionType(t, propName, true /*skipObjectFunctionPropertyAugment*/); prop != nil && c.isNeverReducedProperty(prop) {
return true
Expand Down
Loading