Fix #78079

* mcs/expression.cs (Binary.DoNumericPromotions): Remove and rewrite.
(Binary.OverloadResolve_PredefinedIntegral): New.
(Binary.OverloadResolve_PredefinedFloating): New.
(Binary.OverloadResolve_PredefinedString): New.
(Binary.ResolveOperator): Use those instead of DoNumericPromotions.
Follow the standard more closely, and treat numeric promotions in
terms of overload resolution.
(Binary.CheckShiftArguments): Simplify.
* gmcs/expression.cs: Likewise.
* tests/test-520.cs: New test from #78079.

svn path=/trunk/mcs/; revision=61405

1 files changed, 15 insertions, 0 deletions

diff --git a/mcs/tests/test-520.cs b/mcs/tests/test-520.cs
new file mode 100644
index 00000000000..831f200e669
--- /dev/null
+++ b/mcs/tests/test-520.cs
@@ -0,0 +1,15 @@
+using System;
+
+class FakeInt {
+	private long _value;
+	public FakeInt (long val) { _value = val; }
+	public static implicit operator long (FakeInt self) { return self._value; }
+}
+
+class MainClass {
+	public static void Main ()
+	{
+		if(new FakeInt (42) != 42)
+			throw new Exception ();
+	}
+}