Unified: Track all local name kinds in one pass

[asgerf]

In Swift there is a single shared namespace for variables, functions, types, modules, etc. This PR updates the Variables.qll pass to track all names at once, and renames it to LocalNameBinding.qll to account for the fact that this is not only for variables anymore.

Also contains some drive-by AST mapping fixes. Commit-by-commit review recommended.

Why not treat different name kinds separately?

Some languages have distinct namespaces for variables and types, but trying to separate them for Swift leads to some complications. For example, we would have trouble resolving the references to C below, where both references would appear to refer to both the variable and the type -- if neither resolution pass knows about the other name kind, it gets hard to reason about shadowing among them.

class C {}
let C = foo()
C(); // call the lambda returned by foo()

let C = foo()
class C {}
C(); // call the constructor of class C

With that said, statement labels (break/continue targets) actually do have their own namespace, even in Swift, which lets us experiment with various solutions to this. I expect we can just add a namespace column to the local name binding module, e.g. so we get accessCand(AstNode n, string namespace, string name); and treat (namespace, name) as the "effective" name of a local. But I've left this for a future PR.

Uncertain scopes

The old VariableAccess class is now called PotentialLocalNameAccess; in a future we will reintroduce something like VariableAccess once we have the pieces needed to define it properly. The "potential" part is due to the fact that the local resolution might pass through a class scope, in which inherited members take precedence over outer lexical scopes:

let x = 1
class A {}

class B {
  class C : A {} // 'A' refers to 'B.A' if it exists, otherwise the top-level `A`

 func foo() {
    x // Refers to 'self.x' if it exists, otherwise the top-level 'x'
  }
}

Since types mentioned in the base classes of a class can themselves be resolved through inherited names, we can't build the class hierarchy prior to name binding -- it has to be combined (this will be done in a future PR).

[Copilot]

Pull request overview

Updates Swift name binding to resolve variables, functions, types, modules, and other local names through one unified pass.

Changes:

• Replaces variable-specific APIs with generalized local-name binding.
• Adds scope tests for top-level, class, and generic type names.
• Extracts generic parameters and constraints for nominal Swift types.

Show a summary per file

File	Description
unified/ql/test/library-tests/local-name-binding/top_level.swift	Tests top-level name resolution.
unified/ql/test/library-tests/local-name-binding/test.swift	Adds type-name access coverage.
unified/ql/test/library-tests/local-name-binding/test.ql	Updates the test harness for generalized names.
unified/ql/test/library-tests/local-name-binding/test.expected	Adds expected query outputs.
unified/ql/test/library-tests/local-name-binding/class_scope.swift	Tests class and generic-parameter scopes.
unified/ql/lib/unified.qll	Exports the renamed binding module.
unified/ql/lib/codeql/unified/internal/LocalNameBinding.qll	Implements generalized local-name binding.
unified/ql/lib/codeql/unified/internal/AstExtra.qll	Identifies top-level statements.
unified/extractor/tests/corpus/swift/types/generic-class-parameters-and-constraints.swift	Adds generic-class extraction input.
unified/extractor/tests/corpus/swift/types/generic-class-parameters-and-constraints.output	Records expected generic-class AST output.
unified/extractor/src/languages/swift/swift.rs	Translates nominal-type parameters and constraints.

Review details

Suppressed comments (1)

unified/extractor/src/languages/swift/swift.rs:1168

• protocolDecl has no genericParameterClause field in swift_node_types.yml; SwiftSyntax represents the angle-bracket list as primaryAssociatedTypeClause. Consequently this optional capture is always empty and protocol primary associated-type names are never represented or bound. Please match primaryAssociatedTypeClause and translate its names with the appropriate associated-type semantics.

                genericParameterClause: (genericParameterClause parameters: _* @params)?

• Files reviewed: 10/11 changed files
• Comments generated: 1
• Review effort level: Balanced