merge assembly rewriters into main SMAPI project (#347)

19 files changed, 1123 insertions, 8 deletions

diff --git a/src/StardewModdingAPI/Framework/ModLoading/AssemblyLoader.cs b/src/StardewModdingAPI/Framework/ModLoading/AssemblyLoader.cs
index 9c642bef..27a81038 100644
--- a/src/StardewModdingAPI/Framework/ModLoading/AssemblyLoader.cs
+++ b/src/StardewModdingAPI/Framework/ModLoading/AssemblyLoader.cs
@@ -5,7 +5,6 @@ using System.Linq;
 using System.Reflection;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
-using StardewModdingAPI.AssemblyRewriters;
 using StardewModdingAPI.Framework.Exceptions;
 
 namespace StardewModdingAPI.Framework.ModLoading
@@ -270,8 +269,7 @@ namespace StardewModdingAPI.Framework.ModLoading
                 return;
 
             // get assembly
-            Assembly assembly;
-            if (!this.TypeAssemblies.TryGetValue(type.FullName, out assembly))
+            if (!this.TypeAssemblies.TryGetValue(type.FullName, out Assembly assembly))
                 return;
 
             // replace scope
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs
new file mode 100644
index 00000000..ce234e39
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/EventFinder.cs
@@ -0,0 +1,83 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given event and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class EventFinder : IInstructionRewriter
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The event name for which to find references.</summary>
+        private readonly string EventName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="eventName">The event name for which to find references.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public EventFinder(string fullTypeName, string eventName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.EventName = eventName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName}.{eventName} event";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            return
+                methodRef != null
+                && methodRef.DeclaringType.FullName == this.FullTypeName
+                && (methodRef.Name == "add_" + this.EventName || methodRef.Name == "remove_" + this.EventName);
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/FieldFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/FieldFinder.cs
new file mode 100644
index 00000000..2feaf2e6
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/FieldFinder.cs
@@ -0,0 +1,83 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given field and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class FieldFinder : IInstructionRewriter
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The field name for which to find references.</summary>
+        private readonly string FieldName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="fieldName">The field name for which to find references.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public FieldFinder(string fullTypeName, string fieldName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.FieldName = fieldName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName}.{fieldName} field";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+            return
+                fieldRef != null
+                && fieldRef.DeclaringType.FullName == this.FullTypeName
+                && fieldRef.Name == this.FieldName;
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/MethodFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/MethodFinder.cs
new file mode 100644
index 00000000..c3bb36e3
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/MethodFinder.cs
@@ -0,0 +1,83 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given method and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class MethodFinder : IInstructionRewriter
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The method name for which to find references.</summary>
+        private readonly string MethodName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="methodName">The method name for which to find references.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public MethodFinder(string fullTypeName, string methodName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.MethodName = methodName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName}.{methodName} method";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            return
+                methodRef != null
+                && methodRef.DeclaringType.FullName == this.FullTypeName
+                && methodRef.Name == this.MethodName;
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/PropertyFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/PropertyFinder.cs
new file mode 100644
index 00000000..d1fed84b
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/PropertyFinder.cs
@@ -0,0 +1,83 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given property and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class PropertyFinder : IInstructionRewriter
+    {
+        /*********
+        ** Properties
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+        /// <summary>The property name for which to find references.</summary>
+        private readonly string PropertyName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name for which to find references.</param>
+        /// <param name="propertyName">The property name for which to find references.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public PropertyFinder(string fullTypeName, string propertyName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.PropertyName = propertyName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName}.{propertyName} property";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            return false;
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            return
+                methodRef != null
+                && methodRef.DeclaringType.FullName == this.FullTypeName
+                && (methodRef.Name == "get_" + this.PropertyName || methodRef.Name == "set_" + this.PropertyName);
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Finders/TypeFinder.cs b/src/StardewModdingAPI/Framework/ModLoading/Finders/TypeFinder.cs
new file mode 100644
index 00000000..e67e6766
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Finders/TypeFinder.cs
@@ -0,0 +1,135 @@
+using System.Linq;
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading.Finders
+{
+    /// <summary>Finds incompatible CIL instructions that reference a given type and throws an <see cref="IncompatibleInstructionException"/>.</summary>
+    internal class TypeFinder : IInstructionRewriter
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>The full type name for which to find references.</summary>
+        private readonly string FullTypeName;
+
+
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the instruction finder matches.</summary>
+        public string NounPhrase { get; }
+
+
+        /*********
+        ** Public methods
+        *********/
+        /// <summary>Construct an instance.</summary>
+        /// <param name="fullTypeName">The full type name to match.</param>
+        /// <param name="nounPhrase">A brief noun phrase indicating what the instruction finder matches (or <c>null</c> to generate one).</param>
+        public TypeFinder(string fullTypeName, string nounPhrase = null)
+        {
+            this.FullTypeName = fullTypeName;
+            this.NounPhrase = nounPhrase ?? $"{fullTypeName} type";
+        }
+
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(method))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        public virtual bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged)
+        {
+            if (!this.IsMatch(instruction))
+                return false;
+
+            throw new IncompatibleInstructionException(this.NounPhrase);
+        }
+
+
+        /*********
+        ** Protected methods
+        *********/
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="method">The method deifnition.</param>
+        protected bool IsMatch(MethodDefinition method)
+        {
+            if (this.IsMatch(method.ReturnType))
+                return true;
+
+            foreach (VariableDefinition variable in method.Body.Variables)
+            {
+                if (this.IsMatch(variable.VariableType))
+                    return true;
+            }
+
+            return false;
+        }
+
+        /// <summary>Get whether a CIL instruction matches.</summary>
+        /// <param name="instruction">The IL instruction.</param>
+        protected bool IsMatch(Instruction instruction)
+        {
+            // field reference
+            FieldReference fieldRef = RewriteHelper.AsFieldReference(instruction);
+            if (fieldRef != null)
+            {
+                return
+                    this.IsMatch(fieldRef.DeclaringType) // field on target class
+                    || this.IsMatch(fieldRef.FieldType); // field value is target class
+            }
+
+            // method reference
+            MethodReference methodRef = RewriteHelper.AsMethodReference(instruction);
+            if (methodRef != null)
+            {
+                return
+                    this.IsMatch(methodRef.DeclaringType) // method on target class
+                    || this.IsMatch(methodRef.ReturnType) // method returns target class
+                    || methodRef.Parameters.Any(p => this.IsMatch(p.ParameterType)); // method parameters
+            }
+
+            return false;
+        }
+
+        /// <summary>Get whether a type reference matches the expected type.</summary>
+        /// <param name="type">The type to check.</param>
+        protected bool IsMatch(TypeReference type)
+        {
+            // root type
+            if (type.FullName == this.FullTypeName)
+                return true;
+
+            // generic arguments
+            if (type is GenericInstanceType genericType)
+            {
+                if (genericType.GenericArguments.Any(this.IsMatch))
+                    return true;
+            }
+
+            // generic parameters (e.g. constraints)
+            if (type.GenericParameters.Any(this.IsMatch))
+                return true;
+
+            return false;
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/IInstructionRewriter.cs b/src/StardewModdingAPI/Framework/ModLoading/IInstructionRewriter.cs
new file mode 100644
index 00000000..9b35cdae
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/IInstructionRewriter.cs
@@ -0,0 +1,38 @@
+using Mono.Cecil;
+using Mono.Cecil.Cil;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>Rewrites CIL instructions for compatibility.</summary>
+    internal interface IInstructionRewriter
+    {
+        /*********
+        ** Accessors
+        *********/
+        /// <summary>A brief noun phrase indicating what the rewriter matches.</summary>
+        string NounPhrase { get; }
+
+
+        /*********
+        ** Methods
+        *********/
+        /// <summary>Rewrite a method definition for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="method">The method definition to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        bool Rewrite(ModuleDefinition module, MethodDefinition method, PlatformAssemblyMap assemblyMap, bool platformChanged);
+
+        /// <summary>Rewrite a CIL instruction for compatibility.</summary>
+        /// <param name="module">The module being rewritten.</param>
+        /// <param name="cil">The CIL rewriter.</param>
+        /// <param name="instruction">The instruction to rewrite.</param>
+        /// <param name="assemblyMap">Metadata for mapping assemblies to the current platform.</param>
+        /// <param name="platformChanged">Whether the mod was compiled on a different platform.</param>
+        /// <returns>Returns whether the instruction was rewritten.</returns>
+        /// <exception cref="IncompatibleInstructionException">The CIL instruction is not compatible, and can't be rewritten.</exception>
+        bool Rewrite(ModuleDefinition module, ILProcessor cil, Instruction instruction, PlatformAssemblyMap assemblyMap, bool platformChanged);
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/IncompatibleInstructionException.cs b/src/StardewModdingAPI/Framework/ModLoading/IncompatibleInstructionException.cs
new file mode 100644
index 00000000..17ec24b1
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/IncompatibleInstructionException.cs
@@ -0,0 +1,35 @@
+using System;
+
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <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>
+        public IncompatibleInstructionException(string nounPhrase)
+            : base($"Found an incompatible CIL instruction ({nounPhrase}).")
+        {
+            this.NounPhrase = nounPhrase;
+        }
+
+        /// <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;
+        }
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/InvalidModStateException.cs b/src/StardewModdingAPI/Framework/ModLoading/InvalidModStateException.cs
index ab11272a..075e237a 100644
--- a/src/StardewModdingAPI/Framework/ModLoading/InvalidModStateException.cs
+++ b/src/StardewModdingAPI/Framework/ModLoading/InvalidModStateException.cs
@@ -1,9 +1,9 @@
-using System;
+using System;
 
 namespace StardewModdingAPI.Framework.ModLoading
 {
     /// <summary>An exception which indicates that something went seriously wrong while loading mods, and SMAPI should abort outright.</summary>
-    public class InvalidModStateException : Exception
+    internal class InvalidModStateException : Exception
     {
         /// <summary>Construct an instance.</summary>
         /// <param name="message">The error message.</param>
diff --git a/src/StardewModdingAPI/Framework/ModLoading/ModMetadataStatus.cs b/src/StardewModdingAPI/Framework/ModLoading/ModMetadataStatus.cs
index 1b2b0b55..ab65f7b4 100644
--- a/src/StardewModdingAPI/Framework/ModLoading/ModMetadataStatus.cs
+++ b/src/StardewModdingAPI/Framework/ModLoading/ModMetadataStatus.cs
@@ -1,4 +1,4 @@
-namespace StardewModdingAPI.Framework.ModLoading
+namespace StardewModdingAPI.Framework.ModLoading
 {
     /// <summary>Indicates the status of a mod's metadata resolution.</summary>
     internal enum ModMetadataStatus
@@ -9,4 +9,4 @@
         /// <summary>The mod cannot be loaded.</summary>
         Failed
     }
-}
\ No newline at end of file
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/Platform.cs b/src/StardewModdingAPI/Framework/ModLoading/Platform.cs
new file mode 100644
index 00000000..45e881c4
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/Platform.cs
@@ -0,0 +1,12 @@
+namespace StardewModdingAPI.Framework.ModLoading
+{
+    /// <summary>The game's platform version.</summary>
+    internal enum Platform
+    {
+        /// <summary>The Linux/Mac version of the game.</summary>
+        Mono,
+
+        /// <summary>The Windows version of the game.</summary>
+        Windows
+    }
+}
diff --git a/src/StardewModdingAPI/Framework/ModLoading/PlatformAssemblyMap.cs b/src/StardewModdingAPI/Framework/ModLoading/PlatformAssemblyMap.cs
new file mode 100644
index 00000000..463f45e8
--- /dev/null
+++ b/src/StardewModdingAPI/Framework/ModLoading/PlatformAssemblyMap.cs
@@ -0,0 +1,55 @@
+using System.Collections.Generic;
+using System.Linq;