Fix a crasher in a variant of #31984.

* mcs/const.cs (Constant.CheckBase): New override that defers the
new-or-override check in case the base type hasn't been populated yet.
(Constant.Define): Ensure the new-or-override check is performed.
* tests/test-341.cs: Update to reflect fix of compiler crash.
* errors/cs0108-12.cs: New test.  Ensure that cs0108 handling occurs when
a constant is defined ahead of time due to forward references.

svn path=/trunk/mcs/; revision=39971

1 files changed, 22 insertions, 0 deletions

diff --git a/mcs/errors/cs0108-12.cs b/mcs/errors/cs0108-12.cs
new file mode 100644
index 00000000000..cfb5e9b6d02
--- /dev/null
+++ b/mcs/errors/cs0108-12.cs
@@ -0,0 +1,22 @@
+// cs0108-12.cs: The keyword new is required on 'Libs.MyLib' because it hides inherited member
+// Line: 18
+// Compiler options: -warnaserror -warn:1
+
+using System;
+using System.Runtime.InteropServices;
+ 
+class Test {
+	[DllImport (Libs.MyLib)]
+	private static extern void foo ();
+ 
+	public static void Main ()
+	{
+	}
+}
+ 
+class Libs : Foo {
+	internal const string MyLib = "SomeLibrary";
+}
+class Foo {
+	internal const string MyLib = "Foo";
+}