Fix Enzyme extension: use targeted inactive rules for operator types

Changed from marking all Function types as inactive (too broad, caused
segfaults in downstream packages) to only marking SciMLOperator abstract
types as inactive. This prevents interference with other packages using
Enzyme while still allowing gradients to flow through operator operations.

Author: ChrisRackauckas

ext/SciMLOperatorsEnzymeExt.jl

@@ -21,15 +21,16 @@ function Enzyme.EnzymeRules.inactive_type(::Type{SciMLOperators.NoKwargFilter})
     return true
 end
 
-# The key insight: Function-typed fields in operators are code (update functions),
-# not differentiable data. Tell Enzyme to treat them as inactive.
-# This prevents Enzyme from trying to differentiate through closure captures.
-function Enzyme.EnzymeRules.inactive_type(::Type{F}) where {F <: Function}
-    return true
-end
+# For operator types with function fields, we need to tell Enzyme that the operators
+# themselves are inactive during forward/reverse passes - the differentiation happens
+# through the mathematical operations (mul!, ldiv!, etc.) not through the operator structures.
+# The function fields (update_func) are just code that computes coefficients.
+
+# Mark specific scalar and matrix operator types that have function fields as inactive
+Enzyme.EnzymeRules.inactive_type(::Type{<:SciMLOperators.AbstractSciMLScalarOperator}) = true
+Enzyme.EnzymeRules.inactive_type(::Type{<:SciMLOperators.AbstractSciMLOperator}) = true
 
 # Note: The actual differentiation will happen through the mathematical operations
-# (mul!, *, +, etc.) which Enzyme knows how to handle natively. The operator
-# structures just orchestrate these operations.
+# (mul!, *, +, etc.) which Enzyme knows how to handle natively.
 
 end # module