add 2-arg hash function (#1054)

* add 2-arg hash function

* rm hashsalt

* Update src/PyCall.jl

---------

Co-authored-by: Steven G. Johnson <stevenj@mit.edu>

src/PyCall.jl

@@ -271,22 +271,22 @@ end
 # computing hashes of PyObjects
 
 const pysalt = hash("PyCall.PyObject") # "salt" to mix in to PyObject hashes
-hashsalt(x) = hash(x, pysalt)
 
-function hash(o::PyObject)
+function hash(o::PyObject, salt::UInt)
+    salt ⊻= pysalt
     if ispynull(o)
-        hashsalt(C_NULL)
+        hash(C_NULL, salt)
     elseif is_pyjlwrap(o)
         # call native Julia hash directly on wrapped Julia objects,
         # since on 64-bit Windows the Python 2.x hash is only 32 bits
-        hashsalt(unsafe_pyjlwrap_to_objref(o))
+        hash(unsafe_pyjlwrap_to_objref(o), salt)
     else
         h = ccall((@pysym :PyObject_Hash), Py_hash_t, (PyPtr,), o)
         if h == -1 # error
             pyerr_clear()
-            return hashsalt(PyPtr(o))
+            return hash(PyPtr(o), salt)
         end
-        hashsalt(h)
+        hash(h, salt)
     end
 end
 

src/precompile.jl

@@ -372,7 +372,6 @@ precompile(Tuple{typeof(getproperty), PyDict{Int64, String, true}, Symbol})
 precompile(Tuple{typeof(getproperty), PyError, Symbol})
 precompile(Tuple{typeof(getproperty), PyObject, String})
 precompile(Tuple{typeof(hash), PyObject})
-precompile(Tuple{typeof(hashsalt), Function})
 precompile(Tuple{typeof(hasproperty), PyObject, String})
 precompile(Tuple{typeof(hasproperty), PyObject, Symbol})
 precompile(Tuple{typeof(hassym), Ptr{Nothing}, Symbol})
@@ -528,4 +527,4 @@ precompile(Tuple{typeof(unsafe_load), Ptr{Ptr{PyObject_struct}}})
 precompile(Tuple{typeof(weakref_callback), Ptr{PyObject_struct}, Ptr{PyObject_struct}})
 precompile(Tuple{typeof(xor), Int64, PyObject})
 precompile(Tuple{typeof(xor), PyObject, Int64})
-precompile(Tuple{typeof(xor), PyObject, PyObject})
+precompile(Tuple{typeof(xor), PyObject, PyObject})