Class: Fusion::Parser

Inherits:
Object
  • Object
show all
Includes:
AST
Defined in:
lib/fusion/parser.rb

Constant Summary collapse

COMPARISON_MEMBERS =

The comparisons desugar to a compare piped into its reading member: a < b → [a, b] | @OP.compare | @OP.lt.

{ lt: "lt", lte: "lte", gt: "gt", gte: "gte" }.freeze
PRIMARY_STARTERS =

Tokens that can begin a unary operand — used to decide whether ! has an operand or is the bare !null.

[:number, :string, :true_kw, :false_kw, :null_kw, :bang, :minus, :slash, :tilde, :lbracket, :lbrace, :lparen, :ident, :at, :atat].freeze
GUARDEDPAT_STARTERS =

Tokens that can begin a guardedpat (used to detect whether ! is followed by a payload pattern or stands alone).

[:number, :string, :true_kw, :false_kw, :null_kw, :minus, :lbracket, :lbrace, :ident].freeze

Constants included from AST

AST::ArrayItem, AST::ArraySpread, AST::Clause, AST::IDENTIFIER, AST::KeyValuePair, AST::ObjectSpread, AST::PatternItem, AST::PatternPair, AST::PatternRest

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tokens) ⇒ Parser

Returns a new instance of Parser.



18
19
20
21
 
# File 'lib/fusion/parser.rb', line 18

def initialize(tokens)
  @toks = tokens
  @i = 0
end

Class Method Details

.parse_file(src, site:) ⇒ Object

Parse a complete program. The lexer and parser report failures by raising ParseError; this single entry point rescues them and returns a standardized syntax_error value, so no caller ever sees a raw Ruby error. site is the syntax_error's {origin:, file:} context.



27
28
29
30
31
32
33
34
35
 
# File 'lib/fusion/parser.rb', line 27

def self.parse_file(src, site:)
  toks = Lexer.new(src).tokens
  p = new(toks)
  expr = p.parse_expr
  p.expect(:eof)
  expr
rescue ParseError => e
  Interpreter::ErrorVal.from_runtime(kind: "syntax_error", **site, operation: "parsing code", input: src, message: e.message)
end

.parse_repl(src, site:) ⇒ Object

Parse one REPL entry — a statement (identifier "=" expr) or a bare expression — returning an AST::Statement::Assignment / AST::Expression, or, like parse_file, a standardized syntax_error value instead of ever raising. The REPL uses the error/non-error distinction to tell "keep editing" (didn't parse yet) from "evaluate now" (a complete statement or expression).



42
43
44
45
46
47
48
49
50
 
# File 'lib/fusion/parser.rb', line 42

def self.parse_repl(src, site:)
  toks = Lexer.new(src).tokens
  p = new(toks)
  entry = p.parse_repl_entry
  p.expect(:eof)
  entry
rescue ParseError => e
  Interpreter::ErrorVal.from_runtime(kind: "syntax_error", **site, operation: "parsing code", input: src, message: e.message)
end

Instance Method Details

#advance ⇒ Object 



568
569
570
 
# File 'lib/fusion/parser.rb', line 568

def advance
  @toks[@i].tap { @i += 1 }
end

#at?(type) ⇒ Boolean

Returns:

  • (Boolean) 


564
565
566
 
# File 'lib/fusion/parser.rb', line 564

def at?(type)
  peek.type == type
end

#expect(type) ⇒ Object

Raises:



572
573
574
575
576
577
 
# File 'lib/fusion/parser.rb', line 572

def expect(type)
  t = peek
  raise ParseError, "Expected #{type} but got #{t.type} (#{t.value.inspect}) at #{t.pos}" unless t.type == type

  advance
end

#fold_operator(operands, member) ⇒ Object

A single-operand run collapses to that operand; otherwise fold n-ary.



261
262
263
 
# File 'lib/fusion/parser.rb', line 261

def fold_operator(operands, member)
  operands.length == 1 ? operands.first : pipe_operator(operands, member)
end

#looks_like_function? ⇒ Boolean

Look ahead from current position (just after "(") to decide if this is a function literal: is there a top-level "=>" before the matching ")"?

Returns:

  • (Boolean) 


398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
 
# File 'lib/fusion/parser.rb', line 398

def looks_like_function?
  depth = 0
  j = @i
  while j < @toks.length
    t = @toks[j]
    case t.type
    when :lparen, :lbracket, :lbrace then depth += 1
    when :rparen, :rbracket, :rbrace
      return false if depth == 0 # hit our closing ) first

      depth -= 1
    when :arrow
      return true if depth == 0
    when :eof
      return false
    end
    j += 1
  end
  false
end

#name_ref(path) ⇒ Object

--- Desugaring helpers ---------------------------------------------------



246
 
# File 'lib/fusion/parser.rb', line 246

def name_ref(path) = Expression::FileRef.new(variety: :name, path: path)

#negate(expr) ⇒ Object

-x: a numeric literal folds to a negative literal; anything else negates.



266
267
268
269
270
271
272
 
# File 'lib/fusion/parser.rb', line 266

def negate(expr)
  if expr.is_a?(Expression::Lit) && expr.value.is_a?(Numeric)
    Expression::Lit.new(value: -expr.value)
  else
    pipe_into(expr, "negate")
  end
end

#op_member(member) ⇒ Object

@OP.member, a shadowable reference.



249
 
# File 'lib/fusion/parser.rb', line 249

def op_member(member) = Expression::Member.new(obj: name_ref("OP"), key: member)

#parse_additive ⇒ Object

A run of +/- folds into one @OP.sum; each - term is negated.



129
130
131
132
133
134
135
136
137
138
139
140
 
# File 'lib/fusion/parser.rb', line 129

def parse_additive
  terms = [parse_multiplicative]
  folded = false
  while at?(:plus) || at?(:minus)
    negated = at?(:minus)
    advance
    term = parse_multiplicative
    terms << (negated ? negate(term) : term)
    folded = true
  end
  folded ? pipe_operator(terms, "sum") : terms.first
end

#parse_and ⇒ Object 



88
89
90
91
92
93
94
95
 
# File 'lib/fusion/parser.rb', line 88

def parse_and
  operands = [parse_equality]
  while at?(:andand)
    advance
    operands << parse_equality
  end
  fold_operator(operands, "and")
end

#parse_array ⇒ Object 



318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
 
# File 'lib/fusion/parser.rb', line 318

def parse_array
  expect(:lbracket)
  items = []
  until at?(:rbracket)
    if at?(:spread)
      advance
      items << ArraySpread.new(value: parse_expr)
    else
      items << ArrayItem.new(value: parse_expr)
    end
    break unless at?(:comma)

    advance
  end
  expect(:rbracket)
  Expression::ArrLit.new(items: items)
end

#parse_arraypat ⇒ Object

p_array (reference.md §2.5). Items are p_guardeds — never error patterns. The grammar's two arms (with / without a rest) become two phases: the loop parses leading items up to an optional single ...rest; once a rest is consumed, the inner loop parses trailing items only, so a second ... lands in parse_guardedpat as an unexpected token. There is no seen_rest flag — "at most one rest" is enforced by the shape of the loop.



488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
 
# File 'lib/fusion/parser.rb', line 488

def parse_arraypat
  expect(:lbracket)
  items = []
  until at?(:rbracket)
    if at?(:spread)
      items << parse_pattern_rest
      while at?(:comma)
        advance
        break if at?(:rbracket) # trailing comma
        raise ParseError, "a pattern may contain at most one `...rest` (at #{peek.pos})" if at?(:spread)

        items << PatternItem.new(pattern: parse_guardedpat)
      end
      break
    end
    items << PatternItem.new(pattern: parse_guardedpat)
    break unless at?(:comma)

    advance
  end
  expect(:rbracket)
  Pattern::PArr.new(items: items)
end

#parse_corepat ⇒ Object 



459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
 
# File 'lib/fusion/parser.rb', line 459

def parse_corepat
  t = peek
  case t.type
  when :number, :string, :true_kw, :false_kw, :null_kw
    advance
    Pattern::PLit.new(value: t.value)
  when :minus
    advance
    Pattern::PLit.new(value: -expect(:number).value) # negative literal
  when :lbracket then parse_arraypat
  when :lbrace then parse_objectpat
  when :ident
    advance
    t.value == "_" ? Pattern::PWild.new(dummy: nil) : Pattern::PBind.new(name: t.value)
  when :bang
    # `!pat` is only valid as a clause's top-level pattern, never inside an
    # array element, object member, or error payload.
    raise ParseError, "`!pat` may only appear as a clause's top-level pattern (at #{t.pos})"
  else
    raise ParseError, "Unexpected token in pattern: #{t.type} at #{t.pos}"
  end
end

#parse_equality ⇒ Object 



97
98
99
100
101
102
103
104
 
# File 'lib/fusion/parser.rb', line 97

def parse_equality
  operands = [parse_ordering]
  while at?(:eqeq)
    advance
    operands << parse_ordering
  end
  fold_operator(operands, "equal")
end

#parse_errpat ⇒ Object 



437
438
439
440
441
442
443
444
 
# File 'lib/fusion/parser.rb', line 437

def parse_errpat
  expect(:bang)
  if GUARDEDPAT_STARTERS.include?(peek.type)
    Pattern::PErr.new(inner: parse_guardedpat)               # "!" guardedpat
  else
    Pattern::PErr.new(inner: Pattern::PWild.new(dummy: nil)) # bare "!" — matches any error, binds nothing
  end
end

#parse_expr ⇒ Object 



69
70
71
 
# File 'lib/fusion/parser.rb', line 69

def parse_expr
  parse_or
end

#parse_fileref ⇒ Object 



307
308
309
310
311
312
313
314
315
316
 
# File 'lib/fusion/parser.rb', line 307

def parse_fileref
  expect(:at)
  return Expression::FileRef.new(variety: :self, path: nil) unless at?(:path)

  # A reference is eligible for builtin/stdlib fallback (:name) iff it has no
  # "../"; downward paths stay eligible, only "../" forces file-only (:path).
  # The lexer produced the whole path as one tight token (see Lexer#try_lex_path).
  path = advance.value
  Expression::FileRef.new(variety: path.include?("..") ? :path : :name, path: path)
end

#parse_function_or_group ⇒ Object

A "(" begins a grouped expression, a function literal, or — when empty — the clause-less function (). A function is a comma-separated list of pattern => expr; we detect one by scanning for a top-level => before the matching ). () matches nothing (so it yields null for any normal input and propagates errors).



368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
 
# File 'lib/fusion/parser.rb', line 368

def parse_function_or_group
  expect(:lparen)
  if at?(:rparen)
    advance
    return Expression::FuncLit.new(clauses: [])
  end
  if looks_like_function?
    clauses = []
    loop do
      pat = parse_pattern
      expect(:arrow)
      body = parse_expr
      clauses << Clause.new(pattern: pat, body: body)

      break if !at?(:comma)

      advance
      break if at?(:rparen) # trailing comma
    end
    expect(:rparen)
    Expression::FuncLit.new(clauses: clauses)
  else
    e = parse_expr
    expect(:rparen)
    e
  end
end

#parse_guardedpat ⇒ Object 



446
447
448
449
450
451
452
453
454
455
456
457
 
# File 'lib/fusion/parser.rb', line 446

def parse_guardedpat
  inner = parse_corepat
  if at?(:question)
    advance
    # A predicate is a full pipe so it may chain functions: `a ? b | c` tests
    # `a | b | c`. It stops at `=>`, `,`, `]`, `}`, `)` like any expression.
    pred = parse_pipe
    Pattern::PGuard.new(inner: inner, pred_expr: pred)
  else
    inner
  end
end

#parse_multiplicative ⇒ Object

A run of *// folds into one @OP.product (each / term inverted); %/// are binary and break the run. Standard left-to-right: a * b % c is (a * b) % c.



144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
 
# File 'lib/fusion/parser.rb', line 144

def parse_multiplicative
  node = parse_pipe
  run = nil # accumulating product-run terms, or nil
  loop do
    if at?(:star) || at?(:slash)
      inverted = at?(:slash)
      advance
      term = parse_pipe
      term = pipe_into(term, "invert") if inverted
      if run
        run << term
      else
        run = [node, term]
      end
    elsif at?(:percent) || at?(:slashslash)
      node = pipe_operator(run, "product") if run
      run = nil
      op = at?(:percent) ? "modulo" : "quotient"
      advance
      node = pipe_operator([node, parse_pipe], op)
    else
      break
    end
  end
  run ? pipe_operator(run, "product") : node
end

#parse_object ⇒ Object

Fixed keys must be distinct (the ObjLit data rule); a repeat is a clean syntax_error. Keys arriving via ...spread are dynamic and not checked.



338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
 
# File 'lib/fusion/parser.rb', line 338

def parse_object
  expect(:lbrace)
  pairs = []
  keys = []
  until at?(:rbrace)
    if at?(:spread)
      advance
      pairs << ObjectSpread.new(value: parse_expr)
    else
      key_tok = expect(:string)
      key = key_tok.value
      raise ParseError, "duplicate key #{key.inspect} (at #{key_tok.pos})" if keys.include?(key)

      keys << key
      expect(:colon)
      pairs << KeyValuePair.new(key: key, value: parse_expr)
    end
    break unless at?(:comma)

    advance
  end
  expect(:rbrace)
  Expression::ObjLit.new(pairs: pairs)
end

#parse_objectpat ⇒ Object

p_object (reference.md §2.5). Leading pairs up to an optional single ...rest, which must come last — only a trailing comma may follow it. Keys must be distinct (the PObj data rule); a repeat is a clean syntax_error.



515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
 
# File 'lib/fusion/parser.rb', line 515

def parse_objectpat
  expect(:lbrace)
  pairs = []
  keys = []
  until at?(:rbrace)
    if at?(:spread)
      pairs << parse_pattern_rest
      advance if at?(:comma) && peek(1)&.type == :rbrace # trailing comma
      unless at?(:rbrace)
        raise ParseError, "in an object pattern, `...rest` must come last (at #{peek.pos})"
      end

      break
    end
    key_pos = peek.pos
    pair = parse_pattern_pair
    raise ParseError, "duplicate key #{pair.key.inspect} (at #{key_pos})" if keys.include?(pair.key)

    keys << pair.key
    pairs << pair
    break unless at?(:comma)

    advance
  end
  expect(:rbrace)
  Pattern::PObj.new(pairs: pairs)
end

#parse_or ⇒ Object

--- Operator sugar (reference §2.7) -------------------------------------- The ladder below desugars every operator to a pipe into an @OP.* member (or, for the map-pipes, a stdlib call). Tightest to loosest:

postfix · unary (! - / ~) · pipe (| |: |? |+) · * / % // · + - · ?? < <= > >= · == · && · ||

@OP.* is a shadowable :name reference, so a local @OP reskins the operators.



79
80
81
82
83
84
85
86
 
# File 'lib/fusion/parser.rb', line 79

def parse_or
  operands = [parse_and]
  while at?(:oror)
    advance
    operands << parse_and
  end
  fold_operator(operands, "or")
end

#parse_ordering ⇒ Object

?? (compare) and the comparisons are binary and left-associative — they do not fold, and a < b < c does not chain (it compares a boolean).



112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
 
# File 'lib/fusion/parser.rb', line 112

def parse_ordering
  node = parse_additive
  loop do
    if at?(:qq)
      advance
      node = pipe_operator([node, parse_additive], "compare")
    elsif COMPARISON_MEMBERS.key?(peek.type)
      member = COMPARISON_MEMBERS[advance.type]
      node = pipe_into(pipe_operator([node, parse_additive], "compare"), member)
    else
      break
    end
  end
  node
end

#parse_pattern ⇒ Object

---- Patterns ---- ---- Pattern grammar (mirrors reference.md §2.5 EBNF) ------------------ pattern = p_error | p_guarded p_error = "!" | "!" p_guarded p_guarded = p_core [ "?" predicate ] p_core = p_literal | p_bind | p_wildcard | p_array | p_object Note: p_core does NOT include p_error. The "no nested !pat" property falls out of the grammar shape — p_error is only reachable from pattern (a clause's top level), never from inside arrays, objects, or another error's payload. No flag-threading is needed.



429
430
431
 
# File 'lib/fusion/parser.rb', line 429

def parse_pattern
  at?(:bang) ? parse_errpat : parse_guardedpat
end

#parse_pattern_pair ⇒ Object

p_pair = string ":" p_guarded



553
554
555
556
557
 
# File 'lib/fusion/parser.rb', line 553

def parse_pattern_pair
  key = expect(:string).value
  expect(:colon)
  PatternPair.new(key: key, pattern: parse_guardedpat)
end

#parse_pattern_rest ⇒ Object

p_rest = "..." [ identifier ] — the single rest binder, shared by array and object patterns. Callers parse it only at a rest position and then continue with items/pairs only, which is what holds a pattern to one rest.



546
547
548
549
550
 
# File 'lib/fusion/parser.rb', line 546

def parse_pattern_rest
  expect(:spread)
  name = at?(:ident) ? advance.value : nil
  PatternRest.new(name: name)
end

#parse_pipe ⇒ Object 



171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
 
# File 'lib/fusion/parser.rb', line 171

def parse_pipe
  node = parse_unary
  loop do
    if at?(:pipe)
      advance
      node = Expression::Pipe.new(left: node, right: parse_unary)
    elsif at?(:pipemap) || at?(:pipefilter) || at?(:pipereduce)
      target = { pipemap: "map", pipefilter: "filter", pipereduce: "reduce" }[peek.type]
      advance
      arg = Expression::ObjLit.new(
        pairs: [
          KeyValuePair.new(key: "c", value: node),
          KeyValuePair.new(key: "f", value: parse_unary),
        ],
      )
      node = Expression::Pipe.new(left: arg, right: name_ref(target))
    else
      break
    end
  end
  node
end

#parse_postfix ⇒ Object 



218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
 
# File 'lib/fusion/parser.rb', line 218

def parse_postfix
  node = parse_primary
  loop do
    if at?(:dot)
      advance
      key = expect(:ident).value
      node = Expression::Member.new(obj: node, key: key)
    elsif at?(:lbracket)
      advance
      idx = parse_expr
      if at?(:equals)
        advance
        value = parse_expr
        expect(:rbracket)
        node = Expression::IndexSet.new(obj: node, idx: idx, value: value)
      else
        expect(:rbracket)
        node = Expression::Index.new(obj: node, idx: idx)
      end
    else
      break
    end
  end
  node
end

#parse_primary ⇒ Object 



274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
 
# File 'lib/fusion/parser.rb', line 274

def parse_primary
  t = peek
  case t.type
  when :number, :string, :true_kw, :false_kw, :null_kw
    advance
    Expression::Lit.new(value: t.value)
  when :lbracket then parse_array
  when :lbrace then parse_object
  when :lparen then parse_function_or_group
  when :ident
    advance
    Expression::Ident.new(name: t.value)
  when :at then parse_fileref
  when :atat then parse_superref
  else raise ParseError, "Unexpected token #{t.type} (#{t.value.inspect}) at #{t.pos}"
  end
end

#parse_repl_entry ⇒ Object

A leading identifier = marks a statement; anything else is an expression. (A bare identifier is itself a valid expression, so the = is the decider.)



54
55
56
57
58
59
60
 
# File 'lib/fusion/parser.rb', line 54

def parse_repl_entry
  if at?(:ident) && peek(1)&.type == :equals
    parse_statement
  else
    parse_expr
  end
end

#parse_statement ⇒ Object

statement = identifier "=" expr (REPL only; files contain one expr)



63
64
65
66
67
 
# File 'lib/fusion/parser.rb', line 63

def parse_statement
  name = expect(:ident).value
  expect(:equals)
  AST::Statement::Assignment.new(name: name, expression: parse_expr)
end

#parse_superref ⇒ Object

@@ is super. Bare @@ is super of the current file's own name; @@name (or a downward @@dir/name) is a stable reference to that name — it skips the sibling name.fsn, resolving builtin → stdlib, so a user's local shadow can't intercept it. @@../… is meaningless (super of an upward path) and falls through to a parse error.

Raises:



297
298
299
300
301
302
303
304
305
 
# File 'lib/fusion/parser.rb', line 297

def parse_superref
  expect(:atat)
  return Expression::FileRef.new(variety: :super, path: nil) unless at?(:path)

  tok = advance
  raise ParseError, "`@@` cannot take an upward path (at #{tok.pos})" if tok.value.include?("..")

  Expression::FileRef.new(variety: :super_name, path: tok.value)
end

#parse_unary ⇒ Object

Unary prefixes: !x builds an error (bare ! is !null); -x negates, /x inverts, ~x is logical not. All bind tighter than |.



200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
 
# File 'lib/fusion/parser.rb', line 200

def parse_unary
  if at?(:bang)
    advance
    PRIMARY_STARTERS.include?(peek.type) ? Expression::ErrLit.new(payload: parse_unary) : Expression::ErrLit.new(payload: nil)
  elsif at?(:minus)
    advance
    negate(parse_unary)
  elsif at?(:slash)
    advance
    pipe_into(parse_unary, "invert")
  elsif at?(:tilde)
    advance
    pipe_into(parse_unary, "not")
  else
    parse_postfix
  end
end

#peek(o = 0) ⇒ Object

---- token helpers ----



560
561
562
 
# File 'lib/fusion/parser.rb', line 560

def peek(o = 0)
  @toks[@i + o]
end

#pipe_into(expr, member) ⇒ Object

expr | @OP.member



252
 
# File 'lib/fusion/parser.rb', line 252

def pipe_into(expr, member) = Expression::Pipe.new(left: expr, right: op_member(member))

#pipe_operator(operands, member) ⇒ Object

[operands...] | @OP.member



255
256
257
258
 
# File 'lib/fusion/parser.rb', line 255

def pipe_operator(operands, member)
  arr = Expression::ArrLit.new(items: operands.map { |e| ArrayItem.new(value: e) })
  Expression::Pipe.new(left: arr, right: op_member(member))
end