c8063c9e41
net-plugin: modularize constants (consts.rs) and sockets (sockets.rs); remove legacy commented socket code; fix unused imports mir: move instruction unit tests to tests/mir_instruction_unit.rs (file lean-up); no semantic changes runner/pyvm: ensure using pre-strip; misc docs updates Build: cargo build ok; legacy cfg warnings remain as before
143 lines
7.5 KiB
Markdown
143 lines
7.5 KiB
Markdown
# Nyash Grammar (Stage‑2 EBNF)
|
||
|
||
Status: Fixed for Phase 15 Stage‑2. Parser implementations (Rust/Python/Nyash selfhost) should conform to this subset.
|
||
|
||
program := stmt* EOF
|
||
|
||
stmt := 'return' expr
|
||
| 'local' IDENT '=' expr
|
||
| 'if' expr block ('else' block)?
|
||
| 'loop' '('? expr ')' ? block
|
||
| expr ; expression statement
|
||
|
||
block := '{' stmt* '}'
|
||
|
||
expr := logic
|
||
logic := compare (('&&' | '||') compare)*
|
||
compare := sum (( '==' | '!=' | '<' | '>' | '<=' | '>=' ) sum)?
|
||
sum := term (('+' | '-') term)*
|
||
term := unary (('*' | '/') unary)*
|
||
unary := ('-' | '!' | 'not') unary | factor
|
||
|
||
factor := INT
|
||
| STRING
|
||
| IDENT call_tail*
|
||
| '(' expr ')'
|
||
| 'new' IDENT '(' args? ')'
|
||
| '[' args? ']' ; Array literal (Stage‑1 sugar, gated)
|
||
| '{' map_entries? '}' ; Map literal (Stage‑2 sugar, gated)
|
||
| match_expr ; Pattern matching (replaces legacy peek)
|
||
|
||
match_expr := 'match' expr '{' match_arm+ default_arm? '}'
|
||
match_arm := pattern guard? '=>' (expr | block) ','?
|
||
default_arm:= '_' '=>' (expr | block) ','?
|
||
|
||
pattern := '_'
|
||
| STRING | INT | 'true' | 'false' | 'null'
|
||
| IDENT '(' IDENT? ')' ; Type pattern e.g., StringBox(s)
|
||
| '[' (IDENT (',' '..' IDENT)? )? ']'
|
||
| '{' ( (STRING|IDENT) ':' IDENT (',' '..')? )? '}'
|
||
| pattern '|' pattern ; OR pattern (same arm)
|
||
|
||
guard := 'if' expr
|
||
|
||
map_entries := (STRING | IDENT) ':' expr (',' (STRING | IDENT) ':' expr)* [',']
|
||
|
||
call_tail := '.' IDENT '(' args? ')' ; method
|
||
| '(' args? ')' ; function call
|
||
|
||
args := expr (',' expr)*
|
||
|
||
Notes
|
||
- ASI: Newline is the primary statement separator. Do not insert a semicolon between a closed block and a following 'else'.
|
||
- Semicolon (optional): When `NYASH_PARSER_ALLOW_SEMICOLON=1` is set, `;` is accepted as an additional statement separator (equivalent to newline). It is not allowed between `}` and a following `else`.
|
||
- Do‑while: not supported by design. Prefer a single‑entry, pre‑condition loop normalized via sugar (e.g., `repeat N {}` / `until cond {}`) to a `loop` with clear break conditions.
|
||
- Short-circuit: '&&' and '||' must not evaluate the RHS when not needed.
|
||
- Unary minus has higher precedence than '*' and '/'.
|
||
- IDENT names consist of [A-Za-z_][A-Za-z0-9_]*
|
||
- Array literal is enabled when syntax sugar is on (NYASH_SYNTAX_SUGAR_LEVEL=basic|full) or when NYASH_ENABLE_ARRAY_LITERAL=1 is set.
|
||
- Map literal is enabled when syntax sugar is on (NYASH_SYNTAX_SUGAR_LEVEL=basic|full) or when NYASH_ENABLE_MAP_LITERAL=1 is set.
|
||
- Identifier keys (`{name: v}`) are Stage‑3 and require either NYASH_SYNTAX_SUGAR_LEVEL=full or NYASH_ENABLE_MAP_IDENT_KEY=1.
|
||
- Pattern matching: `match` replaces legacy `peek`. MVP supports wildcard `_`, literals, simple type patterns, fixed/variadic array heads `[hd, ..tl]`, simple map key extract `{ "k": v, .. }`, OR patterns, and guards `if`.
|
||
|
||
## Box Members (Phase‑15, env gate: NYASH_ENABLE_UNIFIED_MEMBERS; default ON)
|
||
|
||
This section adds a minimal grammar for Box members (a unified member model) without changing JSON v0/MIR. Parsing is controlled by env `NYASH_ENABLE_UNIFIED_MEMBERS` (default ON; set `0/false/off` to disable).
|
||
|
||
```
|
||
box_decl := 'box' IDENT '{' member* '}'
|
||
|
||
member := stored
|
||
| computed
|
||
| once_decl
|
||
| birth_once_decl
|
||
| method_decl
|
||
| block_as_role ; nyash-mode (block-first) equivalent
|
||
|
||
stored := IDENT ':' TYPE ( '=' expr )?
|
||
; stored property (read/write). No handlers supported.
|
||
|
||
computed := IDENT ':' TYPE ( '=>' expr | block ) handler_tail?
|
||
; computed property (read‑only). Recomputes on each read.
|
||
|
||
once_decl := 'once' IDENT ':' TYPE ( '=>' expr | block ) handler_tail?
|
||
; lazy once. First read computes and caches; later reads return cached value.
|
||
|
||
birth_once_decl:= 'birth_once' IDENT ':' TYPE ( '=>' expr | block ) handler_tail?
|
||
; eager once. Computed during construction (before user birth), in declaration order.
|
||
|
||
method_decl := IDENT '(' params? ')' ( ':' TYPE )? block handler_tail?
|
||
|
||
; nyash-mode (block-first) variant — gated with NYASH_ENABLE_UNIFIED_MEMBERS=1
|
||
block_as_role := block 'as' ( 'once' | 'birth_once' )? IDENT ':' TYPE
|
||
|
||
handler_tail := ( catch_block )? ( cleanup_block )?
|
||
catch_block := 'catch' ( '(' ( IDENT IDENT | IDENT )? ')' )? block
|
||
cleanup_block := 'cleanup' block
|
||
|
||
; Stage‑3 (Phase 1 via normalization gate NYASH_CATCH_NEW=1)
|
||
; Postfix handlers for expressions and calls
|
||
postfix_catch := primary_expr 'catch' ( '(' ( IDENT IDENT | IDENT )? ')' )? block
|
||
postfix_cleanup := primary_expr 'cleanup' block
|
||
```
|
||
|
||
Semantics (summary)
|
||
- stored: O(1) slot read; write via assignment. Initializer (if present) evaluates at construction once.
|
||
- computed: read‑only; each read evaluates the block; assignment is an error unless a setter is explicitly defined.
|
||
- once: first read evaluates the block and caches the value; subsequent reads return the cached value. On exception without a `catch`, the property becomes poisoned and rethrows on later reads (no retries).
|
||
- birth_once: evaluated before the user `birth` body, in declaration order; exceptions without a `catch` abort construction; cycles between `birth_once` members are an error.
|
||
- handlers: `catch/cleanup` are permitted for computed/once/birth_once/method blocks (Stage‑3), not for stored.
|
||
|
||
Lowering (no JSON v0 change)
|
||
- stored → slot
|
||
- computed → synthesize `__get_name():T { try body; catch; finally }`; reads of `obj.name` become `obj.__get_name()`
|
||
- once → add `__name: Option<T>` and emit `__get_name()` with first‑read initialization; on uncaught exception mark poisoned and rethrow on subsequent reads
|
||
- birth_once → add `__name: T` and insert initialization just before user `birth` in declaration order; handlers apply to each initializer
|
||
- method → existing method forms; optional postfix handlers lower to try/catch/finally
|
||
|
||
## Stage‑3 (Gated) Additions
|
||
|
||
Enabled when `NYASH_PARSER_STAGE3=1` for the Rust parser (and via `--stage3`/`NYASH_NY_COMPILER_STAGE3=1` for the selfhost parser):
|
||
|
||
- try/catch/cleanup
|
||
- `try_stmt := 'try' block ('catch' '(' (IDENT IDENT | IDENT | ε) ')' block) ('cleanup' block)?`
|
||
- MVP policy: single `catch` per `try`。
|
||
- `(Type var)` or `(var)` or `()` are accepted for the catch parameter。
|
||
|
||
- Block‑postfix catch/cleanup（Phase 15.5）
|
||
- `block_catch := '{' stmt* '}' ('catch' '(' (IDENT IDENT | IDENT | ε) ')' block)? ('cleanup' block)?`
|
||
- Applies to standalone block statements. Do not attach to `if/else/loop` structural blocks (wrap with a standalone block when needed).
|
||
- Gate: `NYASH_BLOCK_CATCH=1` (or `NYASH_PARSER_STAGE3=1`).
|
||
- throw
|
||
- `throw_stmt := 'throw' expr`
|
||
|
||
- Method‑level postfix catch/cleanup（Phase 15.6, gated）
|
||
- `method_decl := 'method' IDENT '(' params? ')' block ('catch' '(' (IDENT IDENT | IDENT | ε) ')' block)? ('cleanup' block)?`
|
||
- Gate: `NYASH_METHOD_CATCH=1`（または `NYASH_PARSER_STAGE3=1` と同梱）
|
||
|
||
- Member‑level postfix catch/cleanup（Phase 15.6, gated）
|
||
- Applies to computed/once/birth_once in the unified member model: see “Box Members”.
|
||
- Gate: `NYASH_PARSER_STAGE3=1` (shared). Stored members do not accept handlers.
|
||
|
||
These constructs remain experimental; behaviour may degrade to no‑op in some backends until runtime support lands, as tracked in CURRENT_TASK.md.
|