Add Roslyn Analyzer to detect calls to non-existent functions (name mismatch)

[Copilot]

• Understand the issue requirements (detect calling non-existent functions due to name mismatch)
• Explore existing analyzer infrastructure
• Run existing tests to verify baseline
• Create a new analyzer FunctionNotFoundAnalyzer that detects:
  • Calls to activities via CallActivityAsync with non-existent function names
  • Calls to sub-orchestrations via CallSubOrchestratorAsync with non-existent function names
• Add corresponding test cases for the new analyzer (17 tests)
• Update resource strings for the diagnostic messages
• Update AnalyzerReleases.Unshipped.md to track new rules
• Run tests to validate the implementation (all 90 tests pass)
• Run code review and address feedback
  • Added null check for SemanticModel
  • Changed FindOverridingMethod to ClassOverridesMethod returning bool
  • Changed mutable struct to immutable readonly struct with primary constructor
  • Removed unused System.Diagnostics import
• Address code quality suggestions:
  • Use .Where(...) LINQ filter in foreach loops for diagnostics
  • Use .Any(...) in ClassOverridesMethod instead of explicit foreach loop
  • Combine nested if statements for TaskActivity derived classes check
• Security: CodeQL checker timed out but no new security-sensitive code patterns introduced

Original prompt

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This section details on the original issue you should resolve

<issue_title>Roslyn Analyzer should detect calling non-existent functions (due to name mismatch)</issue_title>
<issue_description>Originally reported by #253 </issue_description>

<agent_instructions>inspect and implement correctly and robustly, add corresponding testcases to validate</agent_instructions>

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

• Fixes Roslyn Analyzer should detect calling non-existent functions (due to name mismatch) #326

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[YunchuWang]

@copilot check and address the comments

[Copilot]

@copilot check and address the comments

Addressed the code quality suggestions in commit 7b66c06:

• Used .Where(...) LINQ filter in foreach loops instead of inner if statements
• Used .Any(...) in ClassOverridesMethod instead of explicit foreach loop with early return
• Combined nested if statements for the TaskActivity derived classes check

[Copilot]

Pull request overview

This PR introduces a new Roslyn analyzer (FunctionNotFoundAnalyzer) to detect compile-time mismatches when calling activities or sub-orchestrations with names that don't match any defined functions in the compilation. This helps prevent runtime errors caused by typos or incorrect function names.

Key Changes:

• New analyzer detects non-existent activity and sub-orchestration references
• Comprehensive test coverage with 17 test cases covering various scenarios
• Support for multiple registration patterns (Azure Functions attributes, class-based syntax, lambda/func registrations)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Analyzers/Activities/FunctionNotFoundAnalyzer.cs	Core analyzer implementation that tracks function invocations and definitions across the compilation, reporting diagnostics for mismatches
test/Analyzers.Tests/Activities/FunctionNotFoundAnalyzerTests.cs	Comprehensive test suite covering activity and sub-orchestration scenarios including Durable Functions, class-based, and lambda registrations
src/Analyzers/Resources.resx	Resource strings for diagnostic messages with clear, actionable guidance
src/Analyzers/AnalyzerReleases.Unshipped.md	Documentation for new diagnostic rules DURABLE2003 and DURABLE2004

[YunchuWang]

verified all cases of analyzer work as intended, signing off