61 lines
9.1 KiB
Markdown
61 lines
9.1 KiB
Markdown
# Honey
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Honey is currently bootstrapped with the Bro compiler. the expected development workspace places the Bro project at [`../brolang`](../brolang); consult that project for compiler behavior and documentation.
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style: see the [language guidelines](docs/style.md).
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build Honey from this directory:
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```sh
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bro build
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```
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run a source file with the interpreter:
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```sh
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./build/honey run example.hon
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```
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```hon
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add proc(left, right int) int {
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return left + right
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}
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main proc() int {
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answer :: add(19, 23)
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return answer
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}
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```
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this prints `42`. interpreted `main` must be a top-level function with no parameters; nonvoid results are printed, not used as process exit statuses.
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the native bootstrap accepts either a no-argument `main` or `main proc(init process.Init)`. it supplies `init.io` and `init.args` from native startup `argc`/`argv`. startup scans each argument once into a heap-allocated array of borrowed zero-terminated slices (`process.Args.values: [][;0]u8`), without copying strings. the descriptor array and borrowed strings remain valid until `main` returns; startup then frees the descriptors, including on a fallible return. allocation failure exits with status `2`. `init.args.values.len` includes the executable name, and `init.args.values[index]` directly accesses an argument after a length guard. callers can supply their own `process.Args { values = slices[..] }` for testing.
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source loading uses the supplied `io.Io` for opening, reading, and closing files. `io.open` accepts a borrowed zero-terminated slice (`[;0]u8`), including `init.args.values[index]` without copying its storage. the bootstrap supports checked sentinel-slice construction with `pointer[..length;0]`. `io.read_all(allocator, reader, maximum)` reads to EOF into a caller-owned `ArrayList(u8)`; release it with `arraylist.deinit`. it frees partial storage on error and consumes one extra byte to distinguish an exact-size input from a limit violation. the driver maps `limit_exceeded` to `source_too_large` at its `u32` source-size limit.
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a recursive example is in [programs/factorial.hon](programs/factorial.hon); `./build/honey run programs/factorial.hon` prints `120`.
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the parser supports arithmetic expressions with nested parenthesized groups, such as `a + (b - c) * 2 / 3`. groups control precedence without adding AST nodes; inner expression spans exclude the grouping parentheses. parsing accepts integer division syntax, but type checking requires float operands for `/`.
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function calls are postfix expressions: `f()`, `f(a, b)`, and `factory()(x)`. calls bind tighter than unary and binary arithmetic and can appear in initializers or as expression statements inside function bodies. argument lists allow a trailing comma; newlines remain statement boundaries. type checking validates callable values, argument counts and argument types.
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`true` and `false` are boolean literals; `bool` is available for parameters, storage and results. `==`, `!=`, `<`, `<=`, `>` and `>=` compare compatible numeric operands and produce `bool`; `==` and `!=` also accept boolean operands. comparisons preserve contextual numeric inference without making their operands boolean. arithmetic binds tighter than relational comparisons, which bind tighter than equality; comparisons associate left to right. boolean arithmetic/ordering and string/function/void comparisons are invalid; there is no implicit numeric-to-boolean conversion.
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`if`/`else` supports braced arms, single statements and `else if` chains. conditions must have type `bool`. a braceless guard requires parentheses unless it is a function call: `if (n <= 1) return 1` or `if ready() return`. `else` binds to the nearest `if`; after a braced arm it may start on the next line. branches are represented as AST blocks even when braceless.
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name resolution (`@source/sema`) runs after parsing. it predeclares package names and each block's direct locals, allowing forward references and mutually recursive functions. parameters and top-level function-body locals share a scope; each conditional arm introduces a child scope whose names do not escape it. signatures resolve names in the enclosing package scope. shadowing is forbidden, including reuse of builtin type names (`int`, `float`, `bool`, `string`, `void`); sibling function and arm scopes may independently reuse names.
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`sema.resolve` returns an owned binding table indexed by AST `NodeId`, without modifying the AST. `sema.binding` identifies a declaration, builtin type, or invalid binding carrying its diagnostic ID; nodes with no binding return `.none`. release the result with `sema.deinit`. unknown names and duplicate declarations add source-spanned diagnostics; invalid syntax retains its existing diagnostic identity. same-scope duplicates retain the first declaration for recovery, while forbidden inner declarations invalidate that name's uses rather than silently binding them to an outer declaration.
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type checking (`@source/sema/check`) runs after name resolution. `check.check` borrows the AST and binding table and returns owned per-node types; query with `check.type_of` and release with `check.deinit`. declarations infer their initializer types, including forward references and function aliases; function types identify the declaration supplying the callable signature. annotations must name builtin types; type names are not ordinary values. `void` is valid as a function result, not as a parameter or stored value.
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numeric typing follows contextual rules within Honey's current `int` and `float` families. integer literals can adopt either family; float literals remain float. numeric demands propagate through arithmetic and inferred bindings before undemanded integers default to `int`. conflicting demands are errors; fixed `int` values do not implicitly convert to `float`. `+`, `-`, `*` and unary `-` require compatible numeric operands; `/` requires and supplies float context. `3 / 2`, `3.0 / 2`, and `ratio float :: 3 / 2` are valid; division involving fixed `int` values requires explicit conversion.
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type errors carry source spans and diagnostic identities; invalid operands propagate their existing identity without duplicate errors, while independent expressions, arguments and conditional arms are still checked. inference cycles without a type anchor are diagnosed. function signatures are checked independently of their bodies. bare `return` and same-line `return expression` are supported inside function bodies and must match the declared result type. nonvoid return-path checking is structural: every path must return or terminate in a diagnostic trap, and both conditional successors are considered without constant folding. a missing `else` permits fallthrough, even for a literal `true` condition; a later return can close that path. statements after a return and untaken branches are still type-checked but are not executed.
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`lower.lower` turns the checked AST and binding table into an owned `@source/ir` module. functions, globals, local slots and instruction-result temporaries have explicit IDs; typed instructions execute in source evaluation order and basic blocks end in jump, conditional-branch, return or diagnostic-trap terminators. conditional arms join only when execution can continue; local slots and temporaries are function-wide, without SSA or phi nodes. literals are parsed and strings decoded during lowering; the module retains no AST, binding-table or source-buffer references. release it with `ir.deinit`; keep and reuse the diagnostic store used during lowering so diagnostic IDs remain valid. the IR is target-independent and is intended to feed later native backends as well as the current interpreter.
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`interpreter.run` consumes only IR and returns a value or a diagnostic trap. string values carry a module-local `ir.StringId`, not a slice; resolve bytes with `ir.string_bytes(&module, id)` before releasing the module. decoded bytes and their full backing allocations remain module-owned, without copying strings during calls or returns. heap-backed invocation frames track their current block and resume it after calls or global initialization. parameters are initialized on entry and locals execute in statement order; premature local reads trap. globals initialize lazily on their first read, cache their result for that run, and trap on initialization cycles. integers use signed 64-bit storage with checked arithmetic; floats use 64-bit IEEE arithmetic and comparisons, including NaN behavior. numeric literal overflow and float underflow to zero are diagnosed; representable subnormals are accepted. strings support `\\`, `\"`, `\n`, `\r`, `\t`, `\0` and `\xNN` escapes.
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recoverable source errors do not stop execution of unaffected code. unused invalid functions, globals and conditional arms retain diagnostic traps; reaching invalid code reports its original diagnostic identity. missing-return traps affect only paths that fall through, not arms that already return or trap. diagnostics include the filename, line and byte column. exit status is `0` for clean execution, `1` for source diagnostics or a runtime trap, and `2` for usage or infrastructure failure. native code generation, loops, assignment and boolean logical operators remain unimplemented.
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