Pow type coercion broken

Prerequisites

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• Reduce the issue to a minimal, self-contained, reproducible test case.
  Avoid dependencies to Mathlib or Batteries.
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Description

Pow doesn't do type coercion whereas Sub does.

Context

Could be related to this pull request: https://github.com/leanprover/lean4/pull/2778

Steps to Reproduce

inductive TestType
  | a (value : Float)
  deriving Repr

instance : Coe Float TestType where
  coe x := TestType.a x

instance : Coe TestType Float where
  coe x := 
    let (TestType.a value) := x
    value

instance : HomogeneousPow TestType where
  pow :=
      let pow x y := 
      let (TestType.a value1) := x
      let (TestType.a value2) := y
      TestType.a (value1 ^ value2)
    pow

#eval ((2. : Float) : TestType) ^ ((2. : Float) : TestType) -- `TestType.a 4.000000`
#eval ((2. : Float) : TestType) ^ ((2. : Float)) -- failed to synthesize HPow TestType Float
#eval ((2. : Float)) ^ ((2. : Float) : TestType) -- failed to synthesize HPow TestType Float

Expected behavior:

#eval ((2. : Float) : TestType) ^ ((2. : Float)) -- should return `TestType.a 4.000000`

Actual behavior:

#eval ((2. : Float) : TestType) ^ ((2. : Float)) -- failed to synthesize HPow TestType Float

Versions

using live.lean-lang.org, lean version 4.10.0-rc1

Additional Information

None

Impact

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Run the minimal reproduction on the Lean nightly release and compare Pow's behavior with Sub's coercion behavior. Read pull request #2778 for related context. Done means mixed Float/TestType exponentiation evaluates to TestType.a 4.000000 instead of failing to synthesize HPow TestType Float.