Previous Behavior

TypeScript 5 introduced some breaking changes to the way that implicit type coercion happens in templates, as well as a few other breaking changes. Although we don't currently use TypeScript 5.3.3 in the repo, experimental work in the xplat branch requires building against TypesScript 5+. There are also customers using TypeScript 5+, who are seeing build errors when importing FluentUI.

New Behavior

Fix build errors seen if the repo is updated to TypeScript 5.3.3. This is part of a set of PRs intending to fix all build errors when building against TypeScript 5.3.3.

The fixes fall into a few major categories:

1. Breaking change in TS 4.8: Unconstrained Generics No Longer Assignable to {}.
   • Fixed by adding extends {} constraint to template types that previously had no constraint (effectively extends unknown). The new constraint disallows null and undefined as template parameters, which were never valid values for these type parameters anyways.

     -export type SlotProp<TProps> =
     +export type SlotProp<TProps extends {}> =

2. Breaking change in TS 4.8: Unused Renames in Binding Patterns are Now Errors in Type Signatures.
   • Fixed by adding a parameter name that was accidentally omitted from function definitions:

     -  onPropUpdate: ({ jsonTreeElement: JSONTreeElement }) => void;
     +  onPropUpdate: (args: { jsonTreeElement: JSONTreeElement }) => void;

3. Breaking change in TS 5.0: Forbidden Implicit Coercions in Relational Operators (effectively: can't use <=, >, etc. between Number and number values).
   • Most cases of this appear to be a typo: a function returning Number when it should have been returning number.

     -export function compareDatePart(date1: Date, date2: Date): Number {
     +export function compareDatePart(date1: Date, date2: Date): number {

ℹ️ Note: This is NOT updating the project to use TypeScript 5.3.3, and an update to the TypeScript version is not planned as part of this change. It is only fixing build errors that would occur if it were built against TypeScript 5.3.3.

Related Issue(s)

This PR was split out from a monolith PR that contains all of the changes. I'm not going to publish the monolith PR, but in case it helps to see all of the changes in one place:

• DRAFT: Fix build errors in TypeScript 5.3 #30796

Here are all of the split-out PRs:

• fix(codemods): Fix build errors in TypeScript 5.3.3 #30806
• fix(date-time-utilities): Fix build errors in TypeScript 5.3.3 #30807
• fix(foundation-legacy): Fix build errors in TypeScript 5.3.3 #30808
• fix(react): Fix build errors in TypeScript 5.3.3 #30809
• fix(react-calendar-compat): Fix build errors in TypeScript 5.3.3 #30810
• fix(react-charting): Fix build errors in TypeScript 5.3.3 #30811
• fix(react-experiments): Fix build errors in TypeScript 5.3.3 #30812
• fix(react-hooks): Fix build errors in TypeScript 5.3.3 #30813
• fix(utilities): Fix build errors in TypeScript 5.3.3 #30814
• fix(web-components): Fix build errors in TypeScript 5.3.3 #30815
• chore: make storybook 6 work with TypeScript 5.3.3 #30816
• fix(react-northstar, react-bindings, react-builder): Fix build errors in TypeScript 5.3.3 #30817