[GR-16506] Pre-coerce longs for BigDecimal.

PullRequest: truffleruby/956

Author: eregon

spec/truffle/bigdecimal_spec.rb

@@ -12,6 +12,10 @@
 
 describe "BigDecimal" do
 
+  it "pre-coerces long integers" do
+    BigDecimal(3).add(1 << 50, 3).should == BigDecimal('0.113e16')
+  end
+
   describe "bug GR-16506" do
 
     before :each do

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

@@ -32,6 +32,12 @@ public Object coerce(int value,
         return coerce.call(getContext().getCoreLibrary().getBigDecimalOperationsModule(), "coerce_integer_to_bigdecimal", value);
     }
 
+    @Specialization
+    public Object coerce(long value,
+                         @Cached("createPublic()") CallDispatchHeadNode coerce) {
+        return coerce.call(getContext().getCoreLibrary().getBigDecimalOperationsModule(), "coerce_integer_to_bigdecimal", value);
+    }
+
     @Specialization(guards = "isRubyBignum(value)")
     public Object coerceBignum(DynamicObject value,
                          @Cached("createPublic()") CallDispatchHeadNode coerce) {