Fix handling of bad IL in ILScanner (#4044)

While the scanner is not trying to be an IL validator, we should at
least not crash.

* Update IL importer to provide hooks for bad IL (this is mostly to
prevent it from crashing with IndexOutOfRangeExceptions).
* Remove exception throwing from the shared ILImporter (while we might
want to throw most of the time, ILVerify probably doesn't want to).
* Do not crash when trying to determine static bases of instance fields.
* Fix constrained method handling.

1 files changed, 15 insertions, 0 deletions

diff --git a/src/ILVerify/src/ILImporter.Verify.cs b/src/ILVerify/src/ILImporter.Verify.cs
index 806980e8f..fc732a8a2 100644
--- a/src/ILVerify/src/ILImporter.Verify.cs
+++ b/src/ILVerify/src/ILImporter.Verify.cs
@@ -1740,5 +1740,20 @@ namespace Internal.IL
         {
             throw new PlatformNotSupportedException("TypedReference not supported in .NET Core");
         }
+
+        private void ReportInvalidBranchTarget(int targetOffset)
+        {
+            throw new NotImplementedException();
+        }
+
+        private void ReportFallthroughAtEndOfMethod()
+        {
+            throw new NotImplementedException();
+        }
+
+        private void ReportInvalidInstruction(ILOpcode opcode)
+        {
+            throw new NotImplementedException();
+        }
     }
 }