perf(Algebra/Category/ModuleCat/Presheaf): speed up the monoidal pushforward instance

[kbuzzard]

This was one of the slowest declarations to typecheck in mathlib. Replacing an Iso.refl with something more explicit yields something which the kernel finds far easier to swallow. As a bonus we can remove a set_option backward.isDefEq.respectTransparency false.

[github-actions]

PR summary 7293186805

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

---

Declarations diff (regex)

+ pushforward₀OfCommRingCatμIso

You can run this locally as follows

## from your `mathlib4` directory:
git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci

## summary with just the declaration names:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh <optional_commit>

## more verbose report:
../mathlib-ci/scripts/pr_summary/declarations_diff.sh long <optional_commit>

The doc-module for scripts/pr_summary/declarations_diff.sh in the mathlib-ci repository contains some details about this script.

Declarations diff (Lean)

✅ Lean-aware diff — post-build, computed from the Lean environment (commit 7293186).

• +3 new declarations
• −0 removed declarations

+PresheafOfModules.pushforward₀OfCommRingCatμIso
+PresheafOfModules.pushforward₀OfCommRingCatμIso_hom_app
+PresheafOfModules.pushforward₀OfCommRingCatμIso_inv_app

---

Decrease in strong tech debt: (relative, absolute) = (1.00, 0.00)

Current number	Change	Type (strong)
5616	-1	backward.isDefEq.respectTransparency

No changes to weak technical debt.

Current commit 7293186805
Reference commit b86f7b9ebe

This script lives in the mathlib-ci repository. To run it locally, from your mathlib4 directory:

git clone https://github.com/leanprover-community/mathlib-ci.git ../mathlib-ci
../mathlib-ci/scripts/reporting/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).

[kbuzzard]

!radar

[leanprover-radar]

Benchmark results for 7293186 against b86f7b9 are in. There are significant results. @kbuzzard

• ✅ build//instructions: -35.9G (-0.02%)

Large changes (1✅)

• ✅ build/module/Mathlib.Algebra.Category.ModuleCat.Presheaf.PushforwardZeroMonoidal//instructions: -97.3G (-89.47%)