What Toopo refuses, and why

1 contract was written in full and then turned down. Each refusal is published with the measurement it was decided on.

[Toopo](../)

# What we refuse, and why

A registry that only shows what it accepted is a registry whose standard nobody can see. These contracts were written in full — signature, properties, every edge case settled — and then turned down. Each refusal is published with the measurement it rests on, so it can be disagreed with.

## typescript/array/group-by@1

Partition an array into groups by a key computed from each element, keeping the input order everywhere and the key values exactly as the key function returned them.

### Turned down for

permanent rule 7 - nothing trivial in the catalogue

### On this measurement

Map.groupBy answers what this contract requires on all thirty cases of block 4.4, replayed by language.test.ts on Node 24.15.0. Where the language ships the function, the TC39 specification is the contract.

### Kept as

the third prototype the contract format was settled on