Fix type instabilities in compactified methods (due to type mismatch in the uncompactified method) (#265)

```
function x_diag_circuit_noisy_measurement(csize)
    circuit = []
    for i in 1:csize
        push!(circuit, PauliError(i, 0.1))
        push!(circuit, sHadamard(i))
        push!(circuit, sCNOT(i, csize+1))
        push!(circuit, sMZ(csize+1,i))
        push!(circuit, ClassicalXOR((1,(i%6+6)),i))
    end
    return circuit
end

@benchmark pftrajectories(state,circuit) setup=(state=PauliFrame(1000, 1001, 1001); circuit=compactify_circuit(x_diag_circuit_noisy_measurement(1000))) evals=1

Before:
BenchmarkTools.Trial: 10 samples with 1 evaluation.
 Range (min … max):  2.885 ms …  2.962 ms  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):     2.900 ms              ┊ GC (median):    0.00%
 Time  (mean ± σ):   2.912 ms ± 30.387 μs  ┊ GC (mean ± σ):  0.00% ± 0.00%

  █▁ ▁   ▁      ▁    ▁                       ▁          ▁  ▁
  ██▁█▁▁▁█▁▁▁▁▁▁█▁▁▁▁█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█▁▁▁▁▁▁▁▁▁▁█▁▁█ ▁
  2.89 ms        Histogram: frequency by time        2.96 ms <

 Memory estimate: 187.50 KiB, allocs estimate: 4000.

After:
BenchmarkTools.Trial: 749 samples with 1 evaluation.
 Range (min … max):  2.929 ms …  3.097 ms  ┊ GC (min … max): 0.00% … 0.00%
 Time  (median):     2.948 ms              ┊ GC (median):    0.00%
 Time  (mean ± σ):   2.951 ms ± 16.854 μs  ┊ GC (mean ± σ):  0.00% ± 0.00%

        ▃█▆▂
  ▂▂▃▄▅▆█████▅▅▄▄▃▃▄▃▃▃▂▂▁▁▁▂▁▂▂▁▁▁▁▁▁▁▁▁▁▁▂▁▁▁▁▁▁▁▁▁▁▁▁▂▁▂▂ ▃
  2.93 ms        Histogram: frequency by time        3.06 ms <

 Memory estimate: 0 bytes, allocs estimate: 0.
```

Author: Krastanov

src/misc_ops.jl

@@ -133,9 +133,6 @@ struct ClassicalXOR{N} <: AbstractOperation
     bits::NTuple{N,Int}
     "The index of the classical bit that will store the results"
     store::Int
-    function ClassicalXOR(bits, store)
-        tbits = tuple(bits...)
-        n = length(tbits)
-        return new{n}(tbits, store)
-    end
 end
+
+ClassicalXOR(bits,store) = ClassicalXOR{length(bits)}(tuple(bits...),store)

src/pauli_frames.jl

@@ -65,6 +65,7 @@ function apply!(frame::PauliFrame, xor::ClassicalXOR)
         end
         frame.measurements[f, xor.store] = value
     end
+    return frame
 end
 
 function apply!(frame::PauliFrame, op::sMX) # TODO implement a faster direct version

src/sumtypes.jl

@@ -9,6 +9,7 @@ struct SymbolicDataType
     types#::Core.SimpleVector
     fieldnames
     originaltype
+    originaltype_parameterized
 end
 _header(s) = s
 _header(s::SymbolicDataType) = s.name
@@ -19,6 +20,8 @@ _fieldnames(s) = fieldnames(s)
 _fieldnames(s::SymbolicDataType) = s.fieldnames
 _originaltype(s) = s
 _originaltype(s::SymbolicDataType) = s.originaltype
+_originaltype_parameterized(s) = s
+_originaltype_parameterized(s::SymbolicDataType) = s.originaltype_parameterized
 
 """
 ```
@@ -38,7 +41,8 @@ julia> make_variant_deconstruct(sCNOT, :apply!, (:s,))
 """
 function make_variant_deconstruct(type::Union{DataType,SymbolicDataType}, call, preargs=(), postargs=())
     variant = Expr(:call, _symbol(type), _fieldnames(type)...)
-    original = :(($(_originaltype(type)))($(_fieldnames(type)...)))
+    original = :(($(_originaltype_parameterized(type)))($(_fieldnames(type)...)))
+    #:($variant => begin $(Expr(:call, call, preargs..., original, postargs...)); nothing end) # useful when you are searching for type instabilities due to inconsistent output types for a method (usually also pointing to a method not following the conventions of the API)
     :($variant => $(Expr(:call, call, preargs..., original, postargs...)))
 end
 
@@ -94,8 +98,7 @@ function make_sumtype_variant_constructor(type)
     if isa(type, DataType) || isa(type, SymbolicDataType)
         return :( CompactifiedGate(g::$(_header(type))) = CompactifiedGate'.$(_symbol(type))($([:(g.$n) for n in _fieldnames(type)]...)) )
     else
-        #return :( CompactifiedGate(g::$(_header(type))) = (@warn "The operation is of a type that can not be unified, defaulting to slower runtime dispatch" typeof(g); return g) )
-        return :()
+        return :() # this is taken care of by a default constructor that also warns about the failure to compactify
     end
 end
 
@@ -135,15 +138,21 @@ function make_all_sumtype_infrastructure_expr(t::DataType, callsigs)
         push!(concrete_types, ut) # fallback
     end
     sumtype = make_sumtype(concrete_types)
+    @debug "compiling a total of $(length(concrete_types)) concrete types"
     constructors = make_sumtype_variant_constructor.(concrete_types)
     methods = [make_sumtype_method(concrete_types, call, preargs, postargs) for (call, preargs, postargs) in callsigs]
+    modulename = gensym(:CompactifiedGate)
     return quote
+        #module $(modulename)
+        #using QuantumClifford
+        #import QuantumClifford: CompactifiedGate, # todo
         $(concretifier_workarounds_types...)
         $(sumtype.args...) # defining the sum type
         $(constructors...) # creating constructors for the sumtype which turn our concrete types into instance of the sum type
         $(concretifier_additional_constructors...) # creating constructors for the newly generated "workaround" concrete types
-        :( CompactifiedGate(g::AbstractOperation) = (@warn "The operation is of a type that can not be unified, defaulting to slower runtime dispatch" typeof(g); return g) )
+        :(CompactifiedGate(g::AbstractOperation) = (@warn "The operation is of a type that can not be unified, defaulting to slower runtime dispatch" typeof(g); return g) )
         $(methods...)
+        #end
     end
 end
 
@@ -161,7 +170,7 @@ function concretifier(t)
         parameterized_type = t{typeparams...}
         ftypes = parameterized_type.types
         fnames = fieldnames(t)
-        push!(names, SymbolicDataType(name, ftypes, fnames, t))
+        push!(names, SymbolicDataType(name, ftypes, fnames, t, parameterized_type))
         push!(generated_concretetypes, :(
             struct $(name)
                 $([:($n::$t) for (n,t) in zip(fnames,ftypes)]...)