Unified: Use ParameterEx in type inference

[hvitved]

This PR simplifies the type inference library by pulling in ParameterEx. The PR also implements typing for parameters of implicit struct parameters via a new defaultConstructorParameterType plugin predicate.

DCA looks good; a small improvement in call resolution rate.

[Copilot]

🟡 Changes recommended

Swift inferred-property parameters can disappear, and required mutable properties are incorrectly marked as defaulted.

3 open findings

• Preserve inferred-type memberwise initializer parameters · New
• Only mark properties with initializers as defaulted · New
• Fix API documentation typo · New

What changed in this PR

Updates Unified type inference to model explicit and synthesized parameters through ParameterEx.

Changes:

• Extends ParameterEx with type and default-value metadata.
• Refactors type inference declarations and callables around Unified AST types.
• Adds callable return-type support to the generated AST API.

File	Description
unified/​ql/​lib/​utils/​test/​TestUtils.qll	Uses type-inference callable naming.
unified/​ql/​lib/​codeql/​unified/​internal/​typeinference/​TypeInference.qll	Refactors declarations and parameters.
unified/​ql/​lib/​codeql/​unified/​internal/​ParameterEx.qll	Adds parameter type/default metadata.
unified/​ql/​lib/​codeql/​unified/​internal/​AstPluginSwift.qll	Supplies Swift memberwise parameters.
unified/​ql/​lib/​codeql/​unified/​internal/​AstPlugin.qll	Expands the plugin contract.
unified/​ql/​lib/​codeql/​unified/​internal/​Ast.qll	Exposes callable return types.
unified/​extractor/​ast_types.yml	Adds return types to callable schema.

🧠 Review effort: Balanced

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[Copilot]

🟡 Changes recommended

Optional Swift properties are incorrectly reported as lacking synthesized default values.

1 open finding

• Recognize implicit nil defaults for Optional stored properties · New

3 resolved since last review

• Only mark properties with initializers as defaulted
• Preserve inferred-type memberwise initializer parameters
• Fix API documentation typo

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

The new synthesized-parameter inference path lacks direct type-inference coverage.

2 open findings

• Add coverage for synthesized-parameter type inference · New
• Fix missing “has” in comment · New

1 resolved since last review

• Recognize implicit nil defaults for Optional stored properties

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Synthesized parameters mishandle skipped defaults and properties whose types are inferred.

2 open findings

• Infer synthesized initializer parameter types from inferred properties · New
• Match labeled arguments to parameters when defaults are omitted · New

2 resolved since last review

• Add coverage for synthesized-parameter type inference
• Fix missing “has” in comment

🧠 Review effort: Balanced

[asgerf]

I'm slightly worried about having an AST plugin that references type inference.

But come of think of it: is there any harm in considering all of these parameters to have a default? The default constructor is only created when there are no other constructors, so it really shouldn't affect overload resolution. Maybe we can simplify it and resolve my above concern at the same time.

[hvitved]

I'm slightly worried about having an AST plugin that references type inference.

It actually only needs static name binding; does that make you less worried? But if we want to support implicitly typed fields at some point, it will need full type inference.

[asgerf]

But if we want to support implicitly typed fields at some point, it will need full type inference.

Do you mean fields whose type is inferred from its initializer? In that case, we get a free pass because those fields are recognized as having default value, based on the fact that they have an initializer.