[TrimmableTypeMap] Add GetStaticMethodFallbackTypesCore override for desugared default interface methods

[Copilot]

Adds GetStaticMethodFallbackTypesCore override to TrimmableTypeMapTypeManager to support Java 8+ default interface methods desugared by D8/R8.

Problem

TrimmableTypeMapTypeManager did not override GetStaticMethodFallbackTypesCore(). Without this, calls to desugared default interface methods fail with NoSuchMethodError at runtime when using the trimmable type map. This affects any app using Java libraries with default interface methods (Java 8+ feature, very common in modern Android libraries like AndroidX).

Fix

Added the same override that already exists in ManagedTypeManager to TrimmableTypeMapTypeManager:

protected override IReadOnlyList<string>? GetStaticMethodFallbackTypesCore(string jniSimpleReference)
{
    int slash = jniSimpleReference.LastIndexOf('/');
    var desugarType = slash > 0
        ? $"{jniSimpleReference.Substring(0, slash + 1)}Desugar{jniSimpleReference.Substring(slash + 1)}"
        : $"Desugar{jniSimpleReference}";
    return new[] {
        $"{desugarType}$_CC",
        $"{jniSimpleReference}$-CC",
    };
}

This generates two fallback type names for desugared companion classes (Desugar{Type}$_CC and {Type}$-CC) so that JNI static method lookups on desugared default interface methods succeed at runtime.

Tests

Added TrimmableTypeMapTypeManagerTests to tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/ to verify the fallback type generation. The tests use a subclass of TrimmableTypeMapTypeManager (accessible via the existing InternalsVisibleTo in Mono.Android) and cover three cases:

• Type with a single-level package name (e.g. android/app/Activity)
• Type without a package name (e.g. Activity)
• Type with a deep package hierarchy (e.g. com/example/package/MyInterface)

[simonrozsival]

@copilot continue

[Copilot]

@copilot continue

Added the GetStaticMethodFallbackTypesCore override to TrimmableTypeMapTypeManager in c0a25a0. The implementation is a direct copy from ManagedTypeManager, generating the two desugar fallback type names (Desugar...$_CC and ...$-CC) needed for D8/R8-desugared default interface methods.

[Copilot]

Pull request overview

Adds support in the trimmable typemap runtime type manager for resolving Java 8+ desugared default interface method companion classes during JNI static method lookup, preventing runtime NoSuchMethodError when default interface methods are used.

Changes:

• Added GetStaticMethodFallbackTypesCore() override to TrimmableTypeMapTypeManager.
• Implemented desugar companion-class fallback name generation (Desugar{Type}$_CC and {Type}$-CC) consistent with ManagedTypeManager.

[jonathanpeppers]

@copilot we are missing a new test to verify this code path works.

[Copilot]

Added tests in b8d9cca. The new TrimmableTypeMapTypeManagerTests class in tests/Mono.Android-Tests/Mono.Android-Tests/Java.Interop/TrimmableTypeMapTypeManagerTests.cs creates a subclass of TrimmableTypeMapTypeManager (accessible via the existing InternalsVisibleTo in Mono.Android) and verifies the fallback type generation for three cases: type with a package name, type without a package name, and type with a deep package hierarchy.