Add depwarn for .compile

Author: avik-pal

src/dense.jl

@@ -201,6 +201,17 @@ struct AutoReverseDiff{C} <: AbstractADType
     end
 end
 
+function Base.getproperty(ad::AutoReverseDiff, s::Symbol)
+    if s === :compile
+        Base.depwarn(
+            "`ad.compile` where `ad` is `AutoReverseDiff` has been deprecated and \
+             will be removed in v2. Instead it is available as a compile-time \
+             constant as `AutoReverseDiff{true}` or `AutoReverseDiff{false}`.",
+            :getproperty)
+    end
+    return getfield(ad, s)
+end
+
 mode(::AutoReverseDiff) = ReverseMode()
 
 """

test/dense.jl

@@ -118,18 +118,21 @@ end
     @test ad isa AutoReverseDiff
     @test mode(ad) isa ReverseMode
     @test !ad.compile
+    @test_deprecated ad.compile
 
     ad = AutoReverseDiff(; compile = true)
     @test ad isa AbstractADType
     @test ad isa AutoReverseDiff
     @test mode(ad) isa ReverseMode
     @test ad.compile
+    @test_deprecated ad.compile
 
     ad = @inferred AutoReverseDiff(; compile = Val(true))
     @test ad isa AbstractADType
     @test ad isa AutoReverseDiff
     @test mode(ad) isa ReverseMode
     @test ad.compile
+    @test_deprecated ad.compile
 end
 
 @testset "AutoSymbolics" begin