Add test locking down mismatched box;isinst;unbox.any pattern

Author: lambdageek

src/tests/Loader/classloader/generics/ByRefLike/InvalidCSharp.il

@@ -237,6 +237,20 @@
         ret
     }
 
+    .method public hidebysig
+        instance bool BoxIsinstUnboxAny_Mismatch(!T) cil managed
+    {
+        ldarg.1
+        // Begin sequence
+            box !T
+            isinst ByRefLikeType2
+            unbox.any ByRefLikeType2
+        // End sequence
+        pop
+        ldc.i4.0
+        ret
+    }
+
     .method public hidebysig
         instance bool BoxIsinstBranch(!T) cil managed
     {
@@ -443,6 +457,14 @@
     )
 }
 
+.class public sequential ansi sealed beforefieldinit ByRefLikeType2
+    extends [System.Runtime]System.ValueType
+{
+    .custom instance void [System.Runtime]System.Runtime.CompilerServices.IsByRefLikeAttribute::.ctor() = (
+        01 00 00 00
+    )
+}
+
 .class interface public auto ansi abstract InvalidCSharp.EmptyInterface
 {
 }
@@ -755,6 +777,22 @@
         ret
     }
 
+    .method public hidebysig static
+        bool BoxIsinstUnboxAny_Mismatch() cil managed
+    {
+        .locals init (
+            [0] valuetype InvalidCSharp.GenericByRefLike_Over`1<valuetype ByRefLikeType>
+        )
+
+        ldloca.s 0
+        initobj valuetype InvalidCSharp.GenericByRefLike_Over`1<valuetype ByRefLikeType>
+        ldloca.s 0
+        ldloc 0
+        ldfld !0 valuetype InvalidCSharp.GenericByRefLike_Over`1<valuetype ByRefLikeType>::Field
+        call instance bool valuetype InvalidCSharp.GenericByRefLike_Over`1<valuetype ByRefLikeType>::BoxIsinstUnboxAny_Mismatch(!0)
+        ret
+    }
+
     .method public hidebysig static
         bool BoxIsinstBranch() cil managed
     {

src/tests/Loader/classloader/generics/ByRefLike/Validate.cs

@@ -67,6 +67,16 @@ public static void Validate_RecognizedOpCodeSequences_Scenarios()
         Assert.True(Exec.BoxIsinstBranch());
     }
 
+    [Fact]
+    public static void Validate_RecognizedOpCodeSequences_Mismatch()
+    {
+        Console.WriteLine($"{nameof(Validate_RecognizedOpCodeSequences_Mismatch)}...");
+
+        // box !T ; isinst S ; unbox.any S should always be guarded by a box !T ; isinst S;
+        // brtrue/brfalse branch, so if it's ever executed and the types aren't equal that's invalid
+        Assert.Throws<InvalidProgramException>(() => { Exec.BoxIsinstUnboxAny_Mismatch(); });
+    }
+
     [Fact]
     public static void Validate_InvalidOpCode_Scenarios()
     {
@@ -81,6 +91,7 @@ public static void Validate_InvalidOpCode_Scenarios()
 
         // Test that explicitly tries to box a ByRefLike type.
         Assert.Throws<InvalidProgramException>(() => { Exec.BoxAsObject(); });
+
     }
 
     [Fact]
@@ -116,4 +127,4 @@ public static void Validate_MemberDiscoveryViaReflection_ForSpanReadOnlySpan()
         //     Assert.NotNull(m);
         // }
     }
-}
+}