Revert, fix, and add test for fractional-part shrink

hypothesis-python/src/hypothesis/internal/conjecture/shrinking/floats.py

@@ -81,3 +81,10 @@ def run_step(self):
             scaled = self.current * 2**p  # note: self.current may change in loop
             for truncate in [math.floor, math.ceil]:
                 self.consider(truncate(scaled) / 2**p)
+
+        # Now try to minimize the top part of the fraction as an integer. This
+        # basically splits the float as k + x with 0 <= x < 1 and minimizes
+        # k as an integer, but without the precision issues that would have.
+        m, n = self.current.as_integer_ratio()
+        i, r = divmod(m, n)
+        self.call_shrinker(Integer, i, lambda k: self.consider((k * n + r) / n))

hypothesis-python/tests/conjecture/test_float_encoding.py

@@ -209,6 +209,10 @@ def test_shrink_down_to_half():
     assert minimal_from(0.75, lambda x: 0 < x < 1) == 0.5
 
 
+def test_shrink_fractional_part():
+    assert minimal_from(2.5, lambda x: divmod(x, 1)[1] == 0.5) == 1.5
+
+
 def test_does_not_shrink_across_one():
     # This is something of an odd special case. Because of our encoding we
     # prefer all numbers >= 1 to all numbers in 0 < x < 1. For the most part