Force inclusion of lambdas and local functions as opt candidates

An alternative "fix" would be to import these on demand during inlining
discovery, but that would miss early optimizations (like SSA promotion),
which wouldn't make much up for inlining.

Closes #27

Author: dubiousconst282

src/DistIL.Cli/Program.cs

@@ -179,9 +179,9 @@ Multiple patterns can be separated with '|'.
     public void FilterPassCandidates(List<MethodDef> candidates)
     {
         if (FilterUnmarked) {
-            candidates.RemoveAll(m => (GetOptimizeAttr(m) ?? GetOptimizeAttr(m.DeclaringType)) is not true);
+            candidates.RemoveAll(m => (IsMarkedForOpts(m) ?? IsMarkedForOpts(m.DeclaringType)) is not true && !IsGeneratedInnerMethod(m));
 
-            static bool? GetOptimizeAttr(ModuleEntity entity)
+            static bool? IsMarkedForOpts(ModuleEntity entity)
             {
                 foreach (var attr in entity.GetCustomAttribs()) {
                     if (attr.Type.Namespace != "DistIL.Attributes") continue;
@@ -190,6 +190,13 @@ public void FilterPassCandidates(List<MethodDef> candidates)
                 }
                 return null;
             }
+            // Checks if the given method has a mangled lambda or local function name.
+            // We'll forcibly import these in order to enable inlining into marked methods. See #27
+            // - https://github.com/dotnet/roslyn/blob/main/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNames.cs
+            static bool IsGeneratedInnerMethod(MethodDef method)
+            {
+                return method.Name.StartsWith('<') && (method.Name.Contains(">b__") || method.Name.Contains(">g__"));
+            }
         }
         if (MethodFilter != null && MethodFilter.StartsWith('!')) {
             var pred = GetMethodFilter()!;