Fix #2158: Remove PointerType support from CSharpResolver for additions/subtractions.

These have special semantics (number of elements in C# vs. number of bytes in IL), and so pointer arithmetic must go through the special HandlePointerArithmetic() code path --> the normal logic in HandleBinaryNumeric must not ever emit pointer arithmetic.

ICSharpCode.Decompiler.Tests/TestCases/Pretty/UnsafeCode.cs

@@ -340,6 +340,26 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			return p - q;
 		}
 
+		public unsafe long Issue2158a(void* p, void* q)
+		{
+			return (long)p - (long)q;
+		}
+
+		public unsafe long Issue2158b(sbyte* p, sbyte* q)
+		{
+			return (long)p - (long)q;
+		}
+
+		public unsafe long Issue2158c(int* p, int* q)
+		{
+			return (long)p - (long)q;
+		}
+
+		public unsafe long Issue2158d(SimpleStruct* p, SimpleStruct* q)
+		{
+			return (long)p - (long)q;
+		}
+
 		public unsafe double FixedMemberAccess(StructWithFixedSizeMembers* m, int i)
 		{
 			return (double)m->Integers[i] + m->Doubles[i];

ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

@@ -1152,7 +1152,7 @@ namespace ICSharpCode.Decompiler.CSharp
 		///   int + ptr
 		///   ptr - int
 		/// Returns null if 'inst' is not performing pointer arithmetic.
-		/// This function not handle 'ptr - ptr'!
+		/// 'ptr - ptr' is not handled here, but in HandlePointerSubtraction()!
 		/// </summary>
 		TranslatedExpression? HandlePointerArithmetic(BinaryNumericInstruction inst, TranslatedExpression left, TranslatedExpression right)
 		{

ICSharpCode.Decompiler/CSharp/Resolver/CSharpResolver.cs

@@ -748,24 +748,6 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 							return BinaryOperatorResolveResult(rhsType, lhs, op, rhs);
 						}
 
-						if (lhsType is PointerType)
-						{
-							methodGroup = new[] {
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.Int32),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.UInt32),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.Int64),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.UInt64)
-							};
-						}
-						else if (rhsType is PointerType)
-						{
-							methodGroup = new[] {
-								PointerArithmeticOperator(rhsType, KnownTypeCode.Int32, rhsType),
-								PointerArithmeticOperator(rhsType, KnownTypeCode.UInt32, rhsType),
-								PointerArithmeticOperator(rhsType, KnownTypeCode.Int64, rhsType),
-								PointerArithmeticOperator(rhsType, KnownTypeCode.UInt64, rhsType)
-							};
-						}
 						if (lhsType.Kind == TypeKind.Null && rhsType.Kind == TypeKind.Null)
 							return new ErrorResolveResult(SpecialType.NullType);
 					}
@@ -813,28 +795,6 @@ namespace ICSharpCode.Decompiler.CSharp.Resolver
 							return BinaryOperatorResolveResult(rhsType, lhs, op, rhs);
 						}
 
-						if (lhsType is PointerType)
-						{
-							if (rhsType is PointerType)
-							{
-								IType int64 = compilation.FindType(KnownTypeCode.Int64);
-								if (lhsType.Equals(rhsType))
-								{
-									return BinaryOperatorResolveResult(int64, lhs, op, rhs);
-								}
-								else
-								{
-									return new ErrorResolveResult(int64);
-								}
-							}
-							methodGroup = new[] {
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.Int32),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.UInt32),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.Int64),
-								PointerArithmeticOperator(lhsType, lhsType, KnownTypeCode.UInt64)
-							};
-						}
-
 						if (lhsType.Kind == TypeKind.Null && rhsType.Kind == TypeKind.Null)
 							return new ErrorResolveResult(SpecialType.NullType);
 					}