fix Big hashing (#58377)

Author: adienes

base/gmp.jl

@@ -848,17 +848,17 @@ if Limb === UInt64 === UInt
     # an optimized version for BigInt of hash_integer (used e.g. for Rational{BigInt}),
     # and of hash
 
-    using .Base: hash_uint
+    using .Base: hash_finalizer
 
     function hash_integer(n::BigInt, h::UInt)
         GC.@preserve n begin
             s = n.size
             s == 0 && return hash_integer(0, h)
             p = convert(Ptr{UInt64}, n.d)
             b = unsafe_load(p)
-            h ⊻= hash_uint(ifelse(s < 0, -b, b) ⊻ h)
+            h ⊻= hash_finalizer(ifelse(s < 0, -b, b) ⊻ h)
             for k = 2:abs(s)
-                h ⊻= hash_uint(unsafe_load(p, k) ⊻ h)
+                h ⊻= hash_finalizer(unsafe_load(p, k) ⊻ h)
             end
             return h
         end

test/gmp.jl

@@ -808,3 +808,11 @@ t = Rational{BigInt}(0, 1)
         @test Base.GMP.MPQ.div!(-oo, zo) == -oz
     end
 end
+
+@testset "hashing" begin
+    for i in 1:10:100
+        bint = big(11)^i
+        bfloat = big(11.0)^i
+        @test (hash(bint) == hash(bfloat)) == (bint == bfloat)
+    end
+end