Revert "[mcs] Don't report error for warnings which are not intended to be compiler warnings. Fixes #33487"mono-4.2.0.207

This reverts commit 6dec86a02329bc46a30b3cdbc8c7bd6554e821de.

2 files changed, 6 insertions, 12 deletions

diff --git a/mcs/errors/cs1904.cs b/mcs/errors/cs1904.cs
index 441753793d4..a551c2a7cde 100644
--- a/mcs/errors/cs1904.cs
+++ b/mcs/errors/cs1904.cs
@@ -1,6 +1,6 @@
-// CS1904: `4013' is not a valid warning number
+// CS1904: `-1' is not a valid warning number
 // Line: 0
-// Compiler options: -nowarn:4014,4013
+// Compiler options: -nowarn:1,-1
 
 class ClassMain {
         public static void Main () {}
diff --git a/mcs/mcs/settings.cs b/mcs/mcs/settings.cs
index 1fa3f376a4d..9b366d636d8 100644
--- a/mcs/mcs/settings.cs
+++ b/mcs/mcs/settings.cs
@@ -583,21 +583,15 @@ namespace Mono.CSharp {
 		{
 			bool valid = true;
 			foreach (string wid in text.Split (numeric_value_separator, StringSplitOptions.RemoveEmptyEntries)) {
-				var warning = wid;
-				if (warning.Length == 6 && warning [0] == 'C' && warning [1] == 'S')
-					warning = warning.Substring (2);
-
 				int id;
-				if (!int.TryParse (warning, NumberStyles.AllowLeadingWhite, CultureInfo.InvariantCulture, out id)) {
+				if (!int.TryParse (wid, NumberStyles.AllowLeadingWhite, CultureInfo.InvariantCulture, out id)) {
+					report.Error (1904, "`{0}' is not a valid warning number", wid);
+					valid = false;
 					continue;
 				}
 
-				if (report.CheckWarningCode (id, Location.Null)) {
+				if (report.CheckWarningCode (id, Location.Null))
 					action (id);
-				} else {
-					report.Error (1904, "`{0}' is not a valid warning number", wid);
-					valid = false;
-				}
 			}
 
 			return valid;