Commits on Sep 19, 2024

1. uniplate_derive: add new Uniplate derive macro …

   Reimplement the uniplate-derive macro to allow for Biplates and
   "multiple type traversals" as discussed in [Niklas Dewally, 2024‐03:
   Implementing Uniplates and Biplates with Structure Preserving Trees].
   (currently at
   https://github.com/conjure-cp/conjure-oxide/wiki/2024%E2%80%9003-Implementing-Uniplates-and-Biplates-with-Structure-Preserving-Trees).
   
   Implementation overview
   =======================
   
   The library syn supports the creation of custom AST nodes. Using the
   Parse trait, one can implement parsers for these custom nodes by
   combining existing Rust AST nodes together as well as parsing Rust
   tokens by hand.
   
   The macro code has two parts: parsing into a custom AST, and using this
   AST for code-gen. This simplifies code-gen, as only the data needed for
   Uniplate is encoded in the AST. This also allows for better error
   reporting, as Most errors are now reported during parsing, allowing
   errors to be associated with the specific tokens that caused them.
   
   The biggest change in Uniplate's AST compared to Rust's is the
   representation of types. Uniplate has three kinds of type: boxed pointer
   types, plateable types, and unpalatable types.
   Plateable types include the current type being derived, or other types
   explicitly specified through the walk_through attribute in the macro
   invocation.
   
   Boxed pointer types represent smart pointers such as Box and Rc. These
   use the .borrow() function instead of & to pass the inner value to the
   Biplate instance. Generating instances for Box<A> and Rc<A> would mean
   that values are constantly moved from stack to heap - this avoids this.
   
   Implementations for standard library iterator types and primitives are
   provided by Uniplate. These implementations are generated by declarative
   macro, allowing easy extension to more collection types in the future.
   
   Testing
   =======
   
   Add trybuild, a library for UI testing derive macros. The Rust tester
   does not run at-all when test code does not compile, but we need to test
   whether our macro gives a compile error when it should. trybuild also
   checks that the error messages given by the compiler have not changed.
   
   Two test ASTs are used for Uniplate and Biplates: a toy
   statement-expression found in the original paper, and the current
   Conjure Oxide AST. Property-based testing in paper.rs shows that
   children() and with_children() work for random homogenous AST's,
   including with boxes and iterators. As these two methods essentially act
   as wrappers for the child tree and context function returned by the
   uniplate() / biplate() methods, this test is sufficient to show that
   automatically derived Uniplate implementations act as intended.
   
   Signed-off-by: Niklas Dewally <niklas@dewally.com>

   

   niklasdewally committed Sep 19, 2024
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2. core: replace manual uniplate impls with derive macro …

   Replace the manual implementation of the Uniplate and Biplate traits for
   the AST with the derive macro.
   
   Adding uniplate_derive to the ast broke is_enum_variant, therefore this
   commit also removes and replaces all invocations of is_xxx() functions
   with let..else or pattern matching.
   
   Signed-off-by: Niklas Dewally <niklas@dewally.com>

   

   niklasdewally committed Sep 19, 2024
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