Fix justActive condition

Closes EnzymeAD#1935

Author: danielwe

src/compiler.jl

@@ -467,7 +467,7 @@ end
 
     subT = fieldtype(T, f)
 
-    if justActive && !allocatedinline(subT)
+    if justActive && ismutabletype(subT)
         return Val(AnyState)
     end
 

test/runtests.jl

@@ -144,6 +144,16 @@ end
     @test Enzyme.Compiler.active_reg_inner(Tuple, (), nothing) == Enzyme.Compiler.DupState
     @test Enzyme.Compiler.active_reg_inner(Tuple, (), nothing, #=justactive=#Val(false), #=unionsret=#Val(false), #=abstractismixed=#Val(true)) == Enzyme.Compiler.MixedState
     @test Enzyme.Compiler.active_reg_inner(Tuple{A,A} where A, (), nothing, #=justactive=#Val(false), #=unionsret=#Val(false), #=abstractismixed=#Val(true)) == Enzyme.Compiler.MixedState
+
+    # issue #1935
+    struct Partial
+        x::Float64
+        box::Core.Box
+        Partial(x) = new(x)  # partial constructor => Base.allocatedinline(Partial) == false
+    end
+    @test Enzyme.Compiler.active_reg_inner(Tuple{Partial}, (), nothing, #=justActive=#Val(false)) == Enzyme.Compiler.MixedState
+    @test Enzyme.Compiler.active_reg_inner(Tuple{Partial}, (), nothing, #=justActive=#Val(true)) == Enzyme.Compiler.ActiveState
+
     world = codegen_world_age(typeof(f0), Tuple{Float64})
     thunk_a = Enzyme.Compiler.thunk(Val(world), Const{typeof(f0)}, Active, Tuple{Active{Float64}}, Val(API.DEM_ReverseModeCombined), Val(1), Val((false, false)), Val(false), Val(false), DefaultABI, Val(false), Val(false))
     thunk_b = Enzyme.Compiler.thunk(Val(world), Const{typeof(f0)}, Const, Tuple{Const{Float64}}, Val(API.DEM_ReverseModeCombined), Val(1), Val((false, false)), Val(false), Val(false), DefaultABI, Val(false), Val(false))