[WIP] Fix DAM annotations applied to never-instantiated types in GetType() calls

[Copilot]

Description

DAM annotations on types are applied when GetType() is called on parameters, even when those types are never instantiated. This keeps unnecessary members in trimmed applications.

[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.NonPublicMethods)]
class C
{
    void Method() { }  // Kept even though C is never instantiated
}

static void Do(C c) => c.GetType();
Do(null);  // C never allocated, but NonPublicMethods applied

Changes

Core Fix:

• HandleCallAction.cs: Check IsInstantiated() before calling ApplyDynamicallyAccessedMembersToTypeHierarchy() in Object_GetType handler

Tests:

• ObjectGetTypeDataflow.cs: Updated expectations for InstantiatedGenericAsSource (IL2075 instead of IL2112)
• Added NeverInstantiatedType test case

Known Issue - Timing

IsInstantiated() may return false during dataflow analysis even for types that will be instantiated, because:

• Instance constructors mark types as instantiated
• Constructor marking may happen after or in different order than GetType() dataflow analysis
• Results in overly conservative behavior (80/81 tests pass)

Recommendation

Investigate OptimizeTypeHierarchyAnnotations - the existing feature designed for this scenario. May need to enable by default or fix implementation bugs rather than adding new timing-sensitive checks.

Testing

• 80/81 DataFlow tests pass
• Failing test confirms conceptual correctness (expects behavior from fix, gets current behavior without it)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>DAM on type gets unnecessarily applied</issue_title>
<issue_description>The NonPublicMethods annotation gets applied here because of the c.GetType call, but since C was never allocated, we shouldn't consider it as returned by the GetType call.

using System.Diagnostics.CodeAnalysis;

Require(typeof(C));
Do(null);

static void Do(C c) => c.GetType();

static void Require([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.NonPublicEvents)] Type t) { }


[DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.NonPublicMethods)]
class C
{
    // The public default constructor is not kept, but this instance method is due to the NonPublicMethods on the type.
    void Method() { }
}
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes DAM on type gets unnecessarily applied #118427

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