Replace lens with microlens{,-mtl,-th}

[langston-barrett]

The motivation is that lens has many, many (transitive) dependencies. This leads to:

• Slow build times (the microlens README claims that it compiles in 3.5s whereas lens takes 4m10s)
• Longer GHC upgrade latency (we have to wait until all of lens's dependencies support a new GHC version)
• Smaller GHC support windows (our GHC support window is limited by that of all of our transitive dependencies)
• Supply chain risks such as lack of maintenance and even supply chain attacks (see recent NPM attacks)

This currently depends on GaloisInc/parameterized-utils#208, it should wait until that PR is merged and released.

[langston-barrett]

Hmm, the build succeeds for me locally, and the error message barely mentions microlens...

[RyanGlScott]

That error message is confusing indeed. It turns out that this happens because one of the test suites depends on singletons-th (via units), and its transitive constraints on th-abstraction conflict with microlens-pro's lower version bounds on th-abstraction. Specifically:

• singletons-th-3.1.1 requires th-desugar-1.14.*, which in turn requires th-abstraction-0.4.*.
• All releases of microlens-pro require th-abstraction-0.6 or later.

To see this a bit more easily:

$ cabal -v0 build what4 --enable-tests -fdRealTestDisable -fsolverTests --minimize-conflict-set --constraint="singletons-th==3.1.1" --constraint="th-desugar==1.14.*" --constraint="th-abstraction==0.4.*"
Error: [Cabal-7107]
Could not resolve dependencies:
[__0] trying: parameterized-utils-2.2.0.0 (user goal)
[__1] next goal: th-abstraction (dependency of parameterized-utils)
[__1] rejecting: th-abstraction; 0.7.2.0, 0.7.1.0, 0.7.0.0, 0.6.0.0, 0.5.0.0 (constraint from command line flag requires >=0.4 && <0.5)
[__1] trying: th-abstraction-0.4.5.0
[__2] next goal: microlens-pro (dependency of parameterized-utils)
[__2] rejecting: microlens-pro-0.2.0.5 (conflict: th-abstraction==0.4.5.0, microlens-pro => th-abstraction>=0.6.0 && <0.8)
[__2] skipping: microlens-pro; 0.2.0.4, 0.2.0.3, 0.2.0.2, 0.2.0.1, 0.2.0, 0.1.0 (has the same characteristics that caused the previous version to fail: excludes 'th-abstraction' version 0.4.5.0)
[__2] fail (backjumping, conflict set: microlens-pro, parameterized-utils, th-abstraction)
After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: th-abstraction, microlens-pro, parameterized-utils

[langston-barrett]

Ah, well perhaps this would be fixed by the next release of parameterized-utils, which drops the dependency on microlens-pro then.