Incorporate symtype in hash for Sym

Author: bowenszhu

src/types.jl

@@ -279,10 +279,10 @@ const ADD_SALT = 0xaddaddaddaddadda % UInt
 const SUB_SALT = 0xaaaaaaaaaaaaaaaa % UInt
 const DIV_SALT = 0x334b218e73bbba53 % UInt
 const POW_SALT = 0x2b55b97a6efb080c % UInt
-function Base.hash(s::BasicSymbolic, salt::UInt)::UInt
+function Base.hash(s::BasicSymbolic{T}, salt::UInt)::UInt where {T}
     E = exprtype(s)
     if E === SYM
-        hash(nameof(s), salt ⊻ SYM_SALT)
+        hash(T, hash(nameof(s), salt ⊻ SYM_SALT))
     elseif E === ADD || E === MUL
         !iszero(salt) && return hash(hash(s, zero(UInt)), salt)
         h = s.hash[]