Fix creating a negative zero BigDecimal in some cases

Author: chrisseaton

spec/ruby/library/bigdecimal/BigDecimal_spec.rb

@@ -154,4 +154,9 @@
     lambda { BigDecimal(1.0) }.should raise_error(ArgumentError)
   end
 
+  it "returns appropriate BigDecimal zero for signed zero" do
+    BigDecimal(-0.0, Float::DIG).sign.should == -1
+    BigDecimal(0.0, Float::DIG).sign.should == 1
+  end
+
 end

spec/tags/library/bigdecimal/to_d_tags.txt

@@ -322,6 +322,10 @@ public static boolean isPositive(double value) {
         return value >= 0;
     }
 
+    public static boolean isNegativeZero(double value) {
+        return Double.valueOf(value).equals(-0.0);
+    }
+
     // Composite
 
     public static boolean isSingletonClass(DynamicObject value) {

src/main/java/org/truffleruby/language/RubyGuards.java

@@ -68,6 +68,7 @@ public BigDecimal doInt(long value, RoundingMode roundingMode) {
     @TruffleBoundary
     @Specialization
     public BigDecimal doDouble(double value, RoundingMode roundingMode) {
+        assert !RubyGuards.isNegativeZero(value);
         return BigDecimal.valueOf(value);
     }
 

src/main/java/org/truffleruby/stdlib/bigdecimal/BigDecimalCastNode.java

@@ -83,21 +83,28 @@ public DynamicObject create(double value, NotProvided digits, boolean strict,
         }
     }
 
-    @Specialization
-    public DynamicObject create(double value, int digits, boolean strict,
-            @Cached("create()") BigDecimalCastNode bigDecimalCastNode,
-            @Cached("createBinaryProfile()") ConditionProfile finiteValueProfile,
-            @Cached("create()") BranchProfile nanProfile,
-            @Cached("create()") BranchProfile positiveInfinityProfile,
-            @Cached("create()") BranchProfile negativeInfinityProfile) {
-        if (finiteValueProfile.profile(Double.isFinite(value))) {
-            final RoundingMode roundMode = getRoundMode();
-            final BigDecimal bigDecimal = (BigDecimal) bigDecimalCastNode.execute(value, roundMode);
+    @Specialization(guards = "isNegativeZero(value)")
+    public DynamicObject createNegativeZero(double value, int digits, boolean strict) {
+        return createSpecialBigDecimal(BigDecimalType.NEGATIVE_ZERO);
+    }
 
-            return createNormalBigDecimal(round(bigDecimal, new MathContext(digits, roundMode)));
-        } else {
-            return createNonFiniteBigDecimal(value, nanProfile, positiveInfinityProfile, negativeInfinityProfile);
-        }
+    @Specialization(guards = {
+            "isFinite(value)",
+            "!isNegativeZero(value)"
+    })
+    public DynamicObject createFinite(double value, int digits, boolean strict,
+                                      @Cached("create()") BigDecimalCastNode bigDecimalCastNode) {
+        final RoundingMode roundMode = getRoundMode();
+        final BigDecimal bigDecimal = (BigDecimal) bigDecimalCastNode.execute(value, roundMode);
+        return createNormalBigDecimal(round(bigDecimal, new MathContext(digits, roundMode)));
+    }
+
+    @Specialization(guards = "!isFinite(value)")
+    public DynamicObject createInfinite(double value, int digits, boolean strict,
+                                        @Cached("create()") BranchProfile nanProfile,
+                                        @Cached("create()") BranchProfile positiveInfinityProfile,
+                                        @Cached("create()") BranchProfile negativeInfinityProfile) {
+        return createNonFiniteBigDecimal(value, nanProfile, positiveInfinityProfile, negativeInfinityProfile);
     }
 
     @Specialization(guards = "type == NEGATIVE_INFINITY || type == POSITIVE_INFINITY")