Support closures (with simple usage of traits)

[coord-e]

• TypeBuilder can't affect mir_ty::Instance::resolve

[Copilot]

Pull request overview

This PR adds support for closures and simple trait usage to the Thrust refinement type system. The changes enable the system to handle closure types, trait method dispatch, and the RustCall ABI used by closures.

• Added support for closure types by treating them as tuples of captured variables
• Implemented RustCall ABI handling with parameter expansion for closure calls
• Enhanced function type resolution to properly handle trait method dispatch through Instance::resolve

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/ui/pass/trait_param.rs	Test for trait-based generic function with correct assertion
tests/ui/pass/trait.rs	Test for direct trait method calls
tests/ui/pass/closure_param.rs	Test for closure passed as function parameter
tests/ui/pass/closure_no_capture.rs	Test for closure without captures
tests/ui/pass/closure_mut_0.rs	Test for closure with mutable captures (no parameters)
tests/ui/pass/closure_mut.rs	Test for closure with mutable captures and parameters
tests/ui/fail/trait_param.rs	Negative test for trait-based generic function
tests/ui/fail/trait.rs	Negative test for trait method calls
tests/ui/fail/closure_param.rs	Negative test for closure parameter handling
tests/ui/fail/closure_no_capture.rs	Negative test for closure without captures
tests/ui/fail/closure_mut_0.rs	Negative test for mutable closure (checks x == 2 when x == 3)
tests/ui/fail/closure_mut.rs	Negative test for mutable closure with parameters
src/rty.rs	Added FunctionAbi enum, abi field to FunctionType, and deref method for RefinedType
src/refine/template.rs	Added closure type handling and ABI tracking in type builders
src/chc.rs	Added boxed helper method for Term construction
src/analyze/crate_.rs	Refactored to use new local_fn_sig method for better closure support
src/analyze/basic_block.rs	Implemented RustCall ABI parameter expansion and closure type handling
src/analyze.rs	Added local_fn_sig methods to extract signatures from MIR for closures

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