Cache the AssemblyQualifiedName property value

[AaronRobinsonMSFT]

This follows the pattern for other names that
are cached on RuntimeType.

Fixes #118389

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[jkotas]

runtime/src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

Lines 3836 to 3840 in a53ffc1

	// This method looks like an attractive inline but expands to two calls,
	// neither of which can be inlined or optimized further. So block it
	// from inlining.
	[MethodImpl(MethodImplOptions.NoInlining)]
	private string? GetCachedName(TypeNameKind kind) => Cache.GetName(kind);

looks like a very questionable comment. We use the Cache property in number of places.

TypeNameKind enum and the overall of structure of this code looks overengineered and unnecessarily inefficient. I am wondering why it cannot be just:

string? AssemblyQualifiedName => Cache.AssemblyQualifiedName;

string? AssemblyQualifiedName => m_assemblyQualifiedName ?? 
     HasRoundtripableFullName(m_runtimeType) ?
         ConstructName(ref m_assemblyQualifiedName, TypeNameFormatFlags.FormatNamespace | TypeNameFormatFlags.FormatFullInst | TypeNameFormatFlags.FormatAssembly) : null;

Dtto for all other names.

[jkotas]

Console.WriteLine(typeof(delegate**).Namespace); is crashing with BadImageFormatException. It should return null instead.

Would you like to fix this one as well in this PR, or is it left for a separate PR? (It should be just about switching order of two lines and adding a test case.)

[jkotas]

Thanks

[AaronRobinsonMSFT]

@ericstj FYI this added some new tests for the Reflection stack and reworked some caching logic in RuntimeType.

[Copilot]

Pull Request Overview

This PR caches the AssemblyQualifiedName property value on RuntimeType to improve performance by avoiding repeated computation. This follows the established pattern where other name properties like Name, FullName, and ToString are already cached.

Key changes include:

• Adding caching for AssemblyQualifiedName property in both CoreCLR and Mono implementations
• Consolidating name formatting logic and improving null handling for function pointers
• Removing unused FormatNoVersion flag from type string formatting

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs	Adds caching for AssemblyQualifiedName, refactors name construction methods, and improves namespace handling
src/mono/System.Private.CoreLib/src/System/RuntimeType.Mono.cs	Updates method signatures to return nullable strings and improves function pointer handling
src/libraries/System.Private.CoreLib/src/System/RuntimeType.cs	Adds shared helper method IsFullNameRoundtripCompatible for consistent name validation
src/coreclr/vm/typestring.h	Removes unused FormatNoVersion flag from type string formatting
src/coreclr/vm/typestring.cpp	Simplifies assembly display name formatting by removing conditional version handling
src/libraries/System.Runtime/tests/System.Reflection.Tests/TypeInfoTests.cs	Adds tests for function pointer FullName and Namespace behavior