With the arrival of generic structs (https://chromium-review.googlesource.com/c/v8/v8/+/1714868) the existing type inference procedure for generic calls became incomplete, since it could not infer types that were only constrained as part of generic types. For instance, given

  struct Box<T: Type> { ... }

  macro unbox<T: type>(box: Box<T>): T

the type argument (Smi) at the following call site

  const box: Box<Smi> = ...;
  unbox(box);

could not be inferred.

This CL re-implements the inference procedure and documents the semantics of type argument inference in Torque a bit more clearly.

R=tebbi@chromium.org

Change-Id: I868f16afbd9864b9c810ac49bc1639b467df939c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1720812
Commit-Queue: Georg Schmid <gsps@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63005}