fix(analysis): resolve alias-call returns and simplify flow assignments

[lewis6991]

• infer_call: infer and apply alias-call substitutions from call-site
  arguments, including colon/dot alignment, so returns like std.Unpack
  are concrete at the call site.
• narrow/get_type_at_flow: drop explicit-annotation precedence and
  antecedent narrowing for assignments; just use the resolved expression
  type.
• stats: prefer declared global type caches for name prefixes so member
  owners attach to their type defs (e.g., stdlib globals).
• tests: add unpack alias-call coverage and a flow regression for
  doc-function assignment narrowing.

[gemini-code-assist]

Summary of Changes

Hello @lewis6991, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refines the type flow analysis by introducing more precise narrowing for function assignments. It ensures that when a function-typed value is assigned to a variable that expects a function signature, the type system correctly narrows the variable's type to that signature, preventing incorrect diagnostic errors and improving type inference accuracy.

Highlights

• Type Narrowing Improvement: Enhanced the type narrowing logic to correctly handle cases where a function-typed source is assigned to a target that expects a signature, ensuring compatibility and more accurate type inference.
• New Test Case: Added test_doc_function_assignment_narrowing to validate the improved type narrowing behavior for function assignments, specifically when a variable can be either an integer or a function.

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Changelog

• crates/emmylua_code_analysis/src/compilation/test/flow.rs
  • Added a new test case test_doc_function_assignment_narrowing to verify the correct type narrowing behavior when a function is assigned to a variable with a union type including a function signature.
• crates/emmylua_code_analysis/src/semantic/infer/narrow/narrow_type/mod.rs
  • Modified the narrow_down_type function to include a new branch for LuaType::Signature. This branch now returns the target type if the source type is identified as a function, facilitating proper type narrowing for function assignments.

Activity

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[gemini-code-assist]

Code Review

This pull request correctly fixes an issue where function assignments did not properly narrow union types, and the added test case effectively validates this. I've suggested a small improvement to also handle narrowing from any and unknown types for consistency with how other types like table are handled.

[gemini-code-assist]

This is a good addition for narrowing function types. However, it doesn't handle cases where the source type is any or unknown. When a variable of type any is assigned a function, its type should be narrowed to that function's type. This is how LuaType::Table is handled, and for consistency, function types should behave similarly.

I suggest also checking for is_any() and is_unknown() on real_source_ref.

Suggested change

	if real_source_ref.is_function() {
	if real_source_ref.is_function() || real_source_ref.is_any() || real_source_ref.is_unknown() {