ECMAScript

TypeScript does not allow developers to import modules with explicit .ts extensions, unlike standard ECMAScript/JavaScript practices. This forces module resolution traversal which is particularly slow over networks, and contradicts TypeScript's own design where the team knows .ts files must be transpiled to .js anyway.

TypeScript's long-term viability depends on TC39's type-annotations proposal, which faces significant consensus issues within the committee itself. The proposal would only treat annotations as comments with no enforcement, leaving TypeScript's theoretical future as a superset uncertain.