Address review comments

src/independentlylinearizedutils.jl

@@ -25,12 +25,19 @@ us = CachePool(Vector{S}, () -> Vector{S}(undef, num_us); thread_safe=false)
     end
 end
 ```
+
+!!! warning "Escaping values"
+    You must not use an acquired value after you have released it;
+    the memory may be immediately re-used by some other consumer of
+    your cache pool.  Do not allow the acquired value to escape
+    outside of the `@with_cache` block, or past a `release!()`.
 """
 mutable struct CachePool{T, THREAD_SAFE}
-    pool::Vector{T}
-    alloc::Function
+    const pool::Vector{T}
+    const alloc::Function
     lock::ReentrantLock
     num_alloced::Int
+    num_acquired::Int
 
     function CachePool(T, alloc::F; thread_safe::Bool = true) where {F}
         return new{T,Val{thread_safe}}(T[], alloc, ReentrantLock(), 0)
@@ -46,6 +53,7 @@ Returns a cached element of the cache pool, calling `cache.alloc()` if none
 are available.
 """
 Base.@inline function acquire!(cache::CachePool{T}, _dummy = nothing) where {T}
+    cache.num_acquired += 1
     if isempty(cache.pool)
         cache.num_alloced += 1
         return cache.alloc()::T
@@ -60,11 +68,17 @@ Returns the value `val` to the cache pool.
 """
 Base.@inline function release!(cache::CachePool, val, _dummy = nothing)
     push!(cache.pool, val)
+    cache.num_acquired -= 1
+end
+
+function is_fully_released(cache::CachePool, _dummy = nothing)
+    return cache.num_acquired == 0
 end
 
 # Thread-safe versions just sub out to the other methods, using `_dummy` to force correct dispatch
 acquire!(cache::ThreadSafeCachePool) = @lock cache.lock acquire!(cache, nothing)
 release!(cache::ThreadSafeCachePool, val) = @lock cache.lock release!(cache, val, nothing)
+is_fully_released(cache::ThreadSafeCachePool) = @lock cache.lock is_fully_released(cache, nothing)
 
 macro with_cache(cache, name, body)
     return quote
@@ -270,8 +284,8 @@ mutable struct IndependentlyLinearizedSolution{T, S, N}
     time_mask::BitMatrix
 
     # Temporary object used during construction, will be set to `nothing` at the end.
-    ilsc::Union{Nothing,IndependentlyLinearizedSolutionChunks{T,S}}
-    ilsc_cache_pool::Union{Nothing,ThreadSafeCachePool{IndependentlyLinearizedSolutionChunksCache{T,S}}}
+    ilsc::Union{Nothing,IndependentlyLinearizedSolutionChunks{T,S,N}}
+    ilsc_cache_pool::Union{Nothing,ThreadSafeCachePool{IndependentlyLinearizedSolutionChunksCache{T,S,N}}}
 end
 # Helper function to create an ILS wrapped around an in-progress ILSC
 function IndependentlyLinearizedSolution(ilsc::IndependentlyLinearizedSolutionChunks{T,S,N}, cache_pool = nothing) where {T,S,N}
@@ -392,14 +406,17 @@ function finish!(ils::IndependentlyLinearizedSolution{T,S}) where {T,S}
     # Update our struct, release the `ilsc` and its caches
     for t_chunk in ilsc.t_chunks
         release!(ilsc.cache.t_chunks, t_chunk)
+        @assert is_fully_released(ilsc.cache.t_chunks)
     end
     for u_idx in 1:length(ilsc.u_chunks)
         for u_chunk in ilsc.u_chunks[u_idx]
             release!(ilsc.cache.u_chunks, u_chunk)
         end
+        @assert is_fully_released(ilsc.cache.u_chunks)
     end
     for time_mask in ilsc.time_masks
         release!(ilsc.cache.time_masks, time_mask)
+        @assert is_fully_released(ilsc.cache.time_masks)
     end
     if ils.ilsc_cache_pool !== nothing
         release!(ils.ilsc_cache_pool, ilsc.cache)