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@trpc/server - Inferrence quirk with ProcedureInputParserCustomValidatorEsque<TInput>

See original GitHub issue

@trpc/server: 7.0.0 Typescript tested: 4.2.4 & 4.3.2

There is a small, but annoying quirk with inference on the ProcedureInputParserCustomValidatorEsque<TInput>:

router()
  .mutation("write", {
    // 1. "a" parameter is inferred as unknown (=correct), but the return type is not inferred up the type tree
    input: (a) => "x",
    // 2. you need to explicitly type (a: unknown), for the inference of return type go up the tree:
    // input: (a: unknown) => "x"
    resolve({input}) {
      // input is resolved as unknown in case 1. and correctly as "string" in 2. case
    }
  })