Types #9
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Types #9
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Switch to 2-phase compilation: 1 phase to build an AST, and another to check types and generate code. Support type annotations, as well as type inference: require annotations on function parameters, and let them be optional on variable definitions and return types. Infer variable types from the initializer expression and return types from the type of the first returned expression. Breaks pretty much every API feature: just working on compilation for now.
Phase 1 builds an AST from the source code. Phase 2 resolves the types and allocates the symbol tables. Phase 3 allocates runtime objects and emits bytecode. Makes 'int' and 'BigInt' separate types. Most everything is broken: as it turns out, designs that work well for a dynamic language are unsuitable for one that is statically-typed.
Start working on classes
At this point, variables with generic types must be treated completely generically. This will allow abstract data types, like 'Vec' and 'Map', but doesn't allow creating, for example, a polymorphic function that sums a list of numbers (either 'int' or 'float'). That behavior will be implemented later, when the codebase becomes stable. Also using the Boehm–Demers–Weiser garbage collector for now (using FetchContent from an unofficial git repo). At some point, paw will get its own garbage collector. At first, it will be a simple tracing GC, like the one we had before static typing was added, except that it needs to coordinate with a custom allocator so it can find pointers (or maintain a lookup table).
Use an AstFolder pass to turn each InstanceDecl into a FuncDecl (the 'stenciler'). Uses the base template, which is fully type checked, along with the concrete types that the instance was instantiated with. Structures are not monomorphied right now. We have a uniform value representation, so it isn't strictly necessary.
Requires that we use extra metadata to distinguish tombstones from vacant/occupied slots (no more type tag that we can use for this purpose). Get more tests to work.
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