2 files changed, 45 insertions, 0 deletions
diff --git a/src/StardewModdingAPI/Framework/AssemblyLoader.cs b/src/StardewModdingAPI/Framework/AssemblyLoader.cs
index 8af67772..dfe0d03f 100644
--- a/src/StardewModdingAPI/Framework/AssemblyLoader.cs
+++ b/src/StardewModdingAPI/Framework/AssemblyLoader.cs
@@ -55,6 +55,7 @@ namespace StardewModdingAPI.Framework
         /// <summary>Preprocess and load an assembly.</summary>
         /// <param name="assemblyPath">The assembly file path.</param>
         /// <returns>Returns the rewrite metadata for the preprocessed assembly.</returns>
+        /// <exception cref="IncompatibleInstructionException">An incompatible CIL instruction was found while rewriting the assembly.</exception>
         public Assembly Load(string assemblyPath)
         {
             // get referenced local assemblies
@@ -159,6 +160,7 @@ namespace StardewModdingAPI.Framework
         /// <summary>Rewrite the types referenced by an assembly.</summary>
         /// <param name="assembly">The assembly to rewrite.</param>
         /// <returns>Returns whether the assembly was modified.</returns>
+        /// <exception cref="IncompatibleInstructionException">An incompatible CIL instruction was found while rewriting the assembly.</exception>
         private bool RewriteAssembly(AssemblyDefinition assembly)
         {
             ModuleDefinition module = assembly.MainModule;
@@ -189,6 +191,22 @@ namespace StardewModdingAPI.Framework
                     this.ChangeTypeScope(type);
             }
 
+            // throw exception if assembly contains incompatible instructions can't be rewritten
+            {
+                IInstructionFinder[] finders = Constants.GetIncompatibilityFinders().ToArray();
+                foreach (MethodDefinition method in this.GetMethods(module))
+                {
+                    foreach (Instruction instruction in method.Body.Instructions)
+                    {
+                        foreach (IInstructionFinder finder in finders)
+                        {
+                            if (finder.IsMatch(instruction, platformChanged))
+                                throw new IncompatibleInstructionException(finder.NounPhrase, $"Found an incompatible CIL instruction ({finder.NounPhrase}) while loading assembly {assembly.Name.Name}.");
+                        }
+                    }
+                }
+            }
+
             // rewrite incompatible instructions
             bool anyRewritten = false;
             IInstructionRewriter[] rewriters = Constants.GetRewriters().ToArray();
diff --git a/src/StardewModdingAPI/Framework/IncompatibleInstructionException.cs b/src/StardewModdingAPI/Framework/IncompatibleInstructionException.cs
new file mode 100644
index 00000000..affe2cb3
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/IncompatibleInstructionException.cs
@@ -0,0 +1,27 @@
+using System;
+
+namespace StardewModdingAPI.Framework
+{
+    /// <summary>An exception raised when an incompatible instruction is found while loading a mod assembly.</summary>
+    internal class IncompatibleInstructionException : Exception
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase which describes the incompatible instruction that was found.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="nounPhrase">A brief noun phrase which describes the incompatible instruction that was found.</param>
+        /// <param name="message">A message which describes the error.</param>
+        public IncompatibleInstructionException(string nounPhrase, string message)
+            : base(message)
+        {
+            this.NounPhrase = nounPhrase;
+        }
+    }
+}