Division unit test fixes

Content.Tests/DMProject/Broken Tests/Tree/Const/Div_Zero/div_zero1.dm

@@ -1,4 +1,4 @@
-// COMPILE ERROR
+// COMPILE ERROR OD0011
 
 var/a = 1 / 0
 

Content.Tests/DMProject/Broken Tests/Tree/Const/Div_Zero/div_zero3.dm

@@ -1,4 +1,4 @@
-// COMPILE ERROR
+// COMPILE ERROR OD0011
 
 var/static/a = 1 / 0
 

Content.Tests/DMProject/Broken Tests/Tree/Const/Div_Zero/div_zero6.dm

@@ -1,4 +1,4 @@
-// COMPILE ERROR
+// COMPILE ERROR OD0011
 
 var/const/a = 0
 var/b = 1 / a

Content.Tests/DMProject/Broken Tests/Tree/Const/Div_Zero/div_zero4.dm → Content.Tests/DMProject/Tests/Tree/Const/Div_Zero/div_zero4.dm

@@ -1,4 +1,4 @@
-// COMPILE ERROR
+// COMPILE ERROR OD0011
 
 /proc/one()
 	return 1

Content.Tests/DMTests.cs

@@ -79,6 +79,7 @@ public void TestFiles(string sourceFile, DMTestFlags testFlags, int errorCode) {
 
             Assert.That(compiledFile is not null && File.Exists(compiledFile), "Failed to compile DM source file");
             Assert.That(_dreamMan.LoadJson(compiledFile), $"Failed to load {compiledFile}");
+            _dreamMan.LastDMException = null; // Nuke any exception from a prior test
             _dreamMan.StartWorld();
 
             (bool successfulRun, DreamValue? returned, Exception? exception) = RunTest();
@@ -114,8 +115,6 @@ public void TestFiles(string sourceFile, DMTestFlags testFlags, int errorCode) {
     }
 
     private (bool Success, DreamValue? Returned, Exception? except) RunTest() {
-        var prev = _dreamMan.LastDMException;
-
         DreamValue? retValue = null;
         Task<DreamValue> callTask = null!;
 
@@ -143,7 +142,7 @@ public void TestFiles(string sourceFile, DMTestFlags testFlags, int errorCode) {
             }
         }
 
-        bool retSuccess = _dreamMan.LastDMException == prev; // Works because "null == null" is true in this language.
+        bool retSuccess = _dreamMan.LastDMException == null; // Works because "null == null" is true in this language.
         return (retSuccess, retValue, _dreamMan.LastDMException);
     }
 

DMCompiler/Optimizer/PeepholeOptimizations.cs

@@ -1,4 +1,5 @@
 using DMCompiler.Bytecode;
+using DMCompiler.Compiler;
 
 // ReSharper disable UnusedType.Global
 
@@ -458,6 +459,10 @@ public void Apply(DMCompiler compiler, List<IAnnotatedBytecode> input, int index
 
         IOptimization.GetInstructionAndValue(input[index + 1], out var pushVal2);
 
+        if (pushVal2 == 0) {
+            compiler.Emit(WarningCode.BadExpression, input[index + 1].GetLocation(), "Division by zero");
+        }
+
         // At runtime, given "A / B" we pop B then A
         // In the peephole optimizer, index is "A", index+1 is "B"
         var args = new List<IAnnotatedBytecode>(1) {new AnnotatedBytecodeFloat(pushVal1 / pushVal2, firstInstruction.Location)};