Emit instantiated types as external references if possible (#105816)

Fixes #105397.

The repro case hits an interesting problem in native layout - we emit the `IEnumerable<IEnumerable<double?>>` type as a constructed type, however the components of it are only generated as necessary. Because native layout expresses it as a decomposed instantiation, we're not able to find the type because the component of it is not constructed and we don't really keep track of those.

This can be fixed by simply not generating types as composed out of various components.

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/EETypeNode.cs

@@ -91,6 +91,7 @@ public EETypeNode(NodeFactory factory, TypeDesc type)
  else if (type.IsCanonicalSubtype(CanonicalFormKind.Any))
  Debug.Assert((this is CanonicalEETypeNode) || (this is NecessaryCanonicalEETypeNode));
 
+ Debug.Assert(!type.IsGenericParameter);
  Debug.Assert(!type.IsRuntimeDeterminedSubtype);
  _type = type;
  _optionalFieldsNode = new EETypeOptionalFieldsNode(this);

src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/DependencyAnalysis/NativeLayoutVertexNode.cs

@@ -232,7 +232,7 @@ internal sealed class NativeLayoutMethodLdTokenVertexNode : NativeLayoutMethodEn
  protected override string GetName(NodeFactory factory) => "NativeLayoutMethodLdTokenVertexNode_" + factory.NameMangler.GetMangledMethodName(_method);
 
  public NativeLayoutMethodLdTokenVertexNode(NodeFactory factory, MethodDesc method)
- : base(factory, method, 0)
+ : base(factory, method, method.IsRuntimeDeterminedExactMethod || method.IsGenericMethodDefinition ? 0 : MethodEntryFlags.CreateInstantiatedSignature)
  {
  }
 

src/tests/nativeaot/SmokeTests/UnitTests/Generics.cs

@@ -58,6 +58,7 @@ internal static int Run()
  Test99198Regression.Run();
  Test102259Regression.Run();
  Test104913Regression.Run();
+ Test105397Regression.Run();
  TestInvokeMemberCornerCaseInGenerics.Run();
  TestRefAny.Run();
  TestNullableCasting.Run();
@@ -3629,6 +3630,31 @@ public static void Run()
  }
  }
 
+ class Test105397Regression
+ {
+ interface IEnumerable<T> { }
+
+ interface ITest<TResult>
+ {
+ TReturn UsingDatabaseResult<TState, TReturn>(TState state, Func<TResult, TState, TReturn> @using);
+ }
+ class Test<TResult> : ITest<TResult>
+ {
+ public TReturn UsingDatabaseResult<TState, TReturn>(TState state, Func<TResult, TState, TReturn> @using)
+ {
+ return default;
+ }
+ }
+
+ struct GenStruct<T> { }
+
+ public static void Run()
+ {
+ ITest<object> t = new Test<object>();
+ t.UsingDatabaseResult<IEnumerable<IEnumerable<GenStruct<double>>>, int>(null, (x, y) => 1);
+ }
+ }
+
  class TestInvokeMemberCornerCaseInGenerics
  {
  class Generic<T>