ReML type bindings

[melsman]

Add support for explicit region and effect abstractions in type bindings.

[Copilot]

Pull request overview

Adds ReML support for explicit region/effect abstractions in type bindings by extending the parser/AST, elaboration, and type-function representations, along with new/updated explicit-region tests.

Changes:

• Extend the grammar and AST to carry explicit region/effect parameters on type bindings and constructed types.
• Update elaboration/type-function machinery to track ReML arity (region/effect var counts) and validate regvar usage.
• Add new explicit-region regression tests and expected outputs.

Reviewed changes

Copilot reviewed 29 out of 30 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
test/explicit_regions/ty1.sml	Updates type-binding syntax to include explicit regvar parameter sequences.
test/explicit_regions/expty3.sml	New test for region-abstract type declarations and application.
test/explicit_regions/expty3.sml.out.ok	Expected output for expty3.sml.
test/explicit_regions/err_ty2.sml	New negative test for repeated abstract regvars in type bindings.
test/explicit_regions/err_ty2.sml.log.ok	Expected error log for err_ty2.sml.
test/explicit_regions/err_ty3.sml	New negative test for free regvar in type binding.
test/explicit_regions/err_ty3.sml.log.ok	Expected error log for err_ty3.sml.
test/explicit_regions/err_expty4.sml	New negative test ensuring applied region-abstract type functions are tracked.
test/explicit_regions/err_expty4.sml.log.ok	Expected error log for err_expty4.sml.
test/explicit_regions/er18.sml.log.ok	Updates expected errors due to new regvar-seq validation.
test/explicit_regions/all.tst	Registers new tests in the explicit-regions test suite.
test/explicit_regions/Makefile	Updates test source list to include new explicit-region tests.
src/Parsing/Topdec.grm	Adds parsing support for regvar sequences in type bindings and prefix regvar type application.
src/Parsing/GrammarUtils.sml	Updates type traversal/rewriting to carry regvar lists on CONty and TYPBIND.
src/Manager/OpacityElim.sml	Adjusts synthetic TYPBIND construction for new regvar-seq payload.
src/Manager/FreeIds.sml	Updates free-id traversal to match new TYPBIND/CONty shapes.
src/Compiler/Lambda/CompileDec.sml	Updates constraint collection traversal for new CONty shape.
src/Common/TyName.sml	Extends TyName with ReML arity tracking and updates pickling.
src/Common/TYNAME.sig	Exposes arity_reml and updates freshTyName signature.
src/Common/STATOBJECT.sml	Updates TypeFcn API to include regvar parameters and ReML arity.
src/Common/ErrorTraverse.sml	Traverses new regvar-seq info and regvars in CONty.
src/Common/ErrorInfo.sml	Adds new error variants/messages for regvar-seq scoping/order and ReML arity mismatches.
src/Common/ElabDec.sml	Implements regvar-seq checks in type bindings and arity checks for regvar application.
src/Common/EfficientElab/StatObject.sml	Extends efficient TypeFcn/TypeScheme instantiation and equality to account for regvars.
src/Common/EfficientElab/Environments.sml	Updates TyName creation and primitive type function construction for new APIs.
src/Common/EfficientElab/ElabTopdec.sml	Updates where type elaboration / TyName creation for new APIs.
src/Common/ERROR_INFO.sml	Signature updates for new explicit-region error constructors.
src/Common/DecGrammar.sml	Updates AST representation, regvar collection, and pretty-printing for regvar-seq/type application.
src/Common/DEC_GRAMMAR.sml	Signature updates for the new typbind/CONty shapes and regvar collection API.

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