1	# src/syntax/bind: where every name in a source is bound, and what every other
2	# name refers to. One walk over the tree threads an environment (the binders
3	# in scope, innermost first) through Bend's binding forms:
4	#   - an item's name (`def f`, `type T`, `law l`, a constructor line);
5	#   - a telescope: a def's parameters, a type's parameters, a constructor's
6	#     fields, each type seeing the names before it;
7	#   - `case p:` patterns and `for x: T` / `exs x: T where P`, for the lines
8	#     under them;
9	#   - a let (`x = v`, `+x = v`, `x : T = v`, `x : T <- m`, `a b = f g`,
10	#     `(a, K{b}) = p`) for the lines after it in its block -- the right side
11	#     sees the outer names, so `st = step(st)` reads the old st;
12	#   - `x => e`, `@x: A -> B` and `&x: A -> B`, for the rest of their sequence.
13	# The walk branches on token and statement kinds, never on a computed test,
14	# so each step recurses on one subtree and the checker accepts it.
15	# A binder shadows an item of the same name; a dotted name is an item of the
16	# file (`text.of`) or, through an import alias, of another file (`Lex.Tok`);
17	# anything else is free (Base, or unknown).
18	import Base
19	import ./lex.bend as Lex
20	import ../lazy/lazy.bend as Lazy
21	import ./tree.bend as Tree
22	
23	# what a binder is: an item's or a constructor's name, a parameter, a type's
24	# parameter, a constructor's field, a let name, a pattern binder, a law's
25	# `for`, or a type-level `@x:` / `&x:`
26	type BindKind is Data:
27	  KItem{}
28	  KCtor{}
29	  KParam{}
30	  KTypeParam{}
31	  KField{}
32	  KLocal{}
33	  KPat{}
34	  KFor{}
35	  KTypeVar{}
36	
37	# KLocal is a name a let, a do-bind or a lambda binds; KPat one bound by a
38	# pattern (a case, or a destructuring let). note: what to show for it -- a
39	# declaration's own text (`+x: U32`), else the line that bound it
40	type Bind is Data:
41	  Bind{name: String, line: U32, col: U32, kind: BindKind, note: String}
42	
43	# what a use refers to: a binder of the file (by position), an item of the
44	# file, an item behind an import alias, or nothing known (Base, or unknown)
45	type Target is Data:
46	  TLocal{line: U32, col: U32}
47	  TItem{name: String}
48	  TQual{alias: String, name: String}
49	  TFree{}
50	
51	# a name that is not a binder, with what it refers to
52	type Use is Data:
53	  Use{name: String, line: U32, col: U32, target: Target}
54	
55	# the names in scope at a statement's line
56	type Scope is Data:
57	  Scope{line: U32, env: List<&2, Bind>}
58	
59	# everything the binder knows about a source, each list in source order
60	type Bound is Data:
61	  Bound{binds: List<&2, Bind>, uses: List<&2, Use>, scopes: List<&2, Scope>}
62	
63	# a line and a column
64	type Pos is Data:
65	  Pos{line: U32, col: U32}
66	
67	# names of the file
68	# -----------------
69	
70	# a name that can be declared: plain, capitalized or dotted
71	def declared.is_name(kk: Lex.TokKind) -> Bool:
72	  match kk:
73	    case Lex.TName{}:
74	      True{}
75	    case Lex.TUpper{}:
76	      True{}
77	    case Lex.TDotted{}:
78	      True{}
79	    case other:
80	      False{}
81	
82	# a leaf's name, when its kind is one: the kind is tested, the text only kept
83	def declared.name(nn: Tree.Node) -> Maybe<&2, String>:
84	  match nn:
85	    case Tree.Leaf{Lex.Tok{k, t, l, c}}:
86	      Bool.pick(Maybe<&2, String>, declared.is_name(k), Some{t}, None{})
87	    case other:
88	      None{}
89	
90	# the item a statement declares: the first name after its keyword
91	def declared.go(kids: Tree.Node) -> Maybe<&2, String>:
92	  match kids:
93	    case Tree.NCons{h, rest}:
94	      declared.name(h)
95	    case other:
96	      None{}
97	
98	# a keyword?
99	def declared.is_key(kk: Lex.TokKind) -> Bool:
100	  match kk:
101	    case Lex.TKey{}:
102	      True{}
103	    case other:
104	      False{}
105	
106	# a keyword leaf? its kind is read, never its text
107	def declared.key(nn: Tree.Node) -> Bool:
108	  match nn:
109	    case Tree.Leaf{Lex.Tok{k, t, l, c}}:
110	      declared.is_key(k)
111	    case other:
112	      False{}
113	
114	# the item a statement declares: the first name after its keyword
115	def declared(kids: Tree.Node) -> Maybe<&2, String>:
116	  match kids:
117	    case Tree.NCons{h, +rest}:
118	      Lazy.either(Maybe<&2, String>, declared.key(h), _u => declared.go(rest), _v => declared(rest))
119	    case other:
120	      None{}
121	
122	# is the name at the head of the list?
123	def push_name.again(acc: List<&2, String>, +name: String) -> Bool:
124	  match acc:
125	    case Nil{}:
126	      False{}
127	    case Con{hh, _rest}:
128	      String.eq(hh, name)
129	
130	# a name, when there is one, onto a list, unless it is the name just put
131	# there: a proof file's `law x` and its `def x` are one item, and every use
132	# no binder holds is looked for in this list
133	def push_name(mm: Maybe<&2, String>, +acc: List<&2, String>) -> List<&2, String>:
134	  match mm:
135	    case None{}:
136	      acc
137	    case Some{+name}:
138	      Lazy.stop(List<&2, String>, push_name.again(acc, name), acc, _u => name <> acc)
139	
140	# a type's constructors: the first name of each line under it
141	def ctors(body: Tree.Node, acc: List<&2, String>) -> List<&2, String>:
142	  match body:
143	    case Tree.NCons{Tree.Stmt{k, kids, b}, rest}:
144	      ctors(rest, push_name(declared.go(kids), acc))
145	    case other:
146	      acc
147	
148	# the defs, laws, types and constructors of a source
149	def items(root: Tree.Node, acc: List<&2, String>) -> List<&2, String>:
150	  match root:
151	    case Tree.NCons{Tree.Stmt{Tree.SDef{}, kids, body}, rest}:
152	      items(rest, push_name(declared(kids), acc))
153	    case Tree.NCons{Tree.Stmt{Tree.SLaw{}, kids, body}, rest}:
154	      items(rest, push_name(declared(kids), acc))
155	    case Tree.NCons{Tree.Stmt{Tree.SType{}, kids, body}, rest}:
156	      items(rest, ctors(body, push_name(declared(kids), acc)))
157	    case Tree.NCons{other, rest}:
158	      items(rest, acc)
159	    case other:
160	      acc
161	
162	# the text of a chain's last leaf
163	def last_text(kids: Tree.Node) -> String:
164	  match kids:
165	    case Tree.NCons{Tree.Leaf{Lex.Tok{k, t, l, c}}, Tree.NNil{}}:
166	      t
167	    case Tree.NCons{h, rest}:
168	      last_text(rest)
169	    case other:
170	      ""
171	
172	# the import aliases of a source: the last token of each `import .. as X`
173	def aliases(root: Tree.Node, +acc: List<&2, String>) -> List<&2, String>:
174	  match root:
175	    case Tree.NCons{Tree.Stmt{Tree.SImport{}, kids, body}, rest}:
176	      +last = last_text(kids)
177	      aliases(rest, Bool.pick(List<&2, String>, Bool.or(String.eq(last, "Base"), String.eq(last, "import")), acc, last <> acc))
178	    case Tree.NCons{other, rest}:
179	      aliases(rest, acc)
180	    case other:
181	      acc
182	
183	# resolution
184	# ----------
185	
186	# the innermost binder of a name in an environment
187	def find(env: List<&2, Bind>, +name: String) -> Maybe<&2, Bind>:
188	  match env:
189	    case Nil{}:
190	      None{}
191	    case Con{Bind{+n, l, c, k, note}, t}:
192	      +more = find(t, name)
193	      Bool.pick(Maybe<&2, Bind>, String.eq(n, name), Some{Bind{n, l, c, k, note}}, more)
194	
195	def head_of.go(cs: List<&2, Char>) -> List<&2, Char>:
196	  match cs:
197	    case Nil{}:
198	      Nil{}
199	    case Con{+c, t}:
200	      Lazy.stop(List<&2, Char>, Char.is_eq(c, '.'), Nil{}, _u => c <> head_of.go(t))
201	
202	# a dotted name's part before the first dot
203	def head_of(cs: List<&2, Char>) -> String:
204	  String.from_list(head_of.go(cs))
205	
206	# a dotted name's part after the first dot
207	def rest_of(cs: List<&2, Char>) -> String:
208	  match cs:
209	    case Nil{}:
210	      ""
211	    case Con{c, +t}:
212	      Lazy.stop(String, Char.is_eq(c, '.'), String.from_list(t), _u => rest_of(t))
213	
214	# is the name among these?
215	def has(names: List<&2, String>, +name: String) -> Bool:
216	  List.contains(~String, ~String.eq, names, name)
217	
218	# two names alike, char by char, stopping at the first that differs:
219	# String.eq, without the pairs String.cmp builds on every step
220	def same(aa: String, bb: String) -> Bool:
221	  match aa bb:
222	    case SNil{} SNil{}:
223	      True{}
224	    case SNil{} SCon{_h2, _t2}:
225	      False{}
226	    case SCon{_h1, _t1} SNil{}:
227	      False{}
228	    case SCon{h1, t1} SCon{h2, t2}:
229	      Lazy.and_then(Char.is_eq(h1, h2), _u => same(t1, t2))
230	
231	# is the name among the file's items? `has`, stopping at the first hit, as
232	# every use no binder holds asks it of every item
233	def has_item(names: List<&2, String>, +name: String) -> Bool:
234	  match names:
235	    case Nil{}:
236	      False{}
237	    case Con{hh, rest}:
238	      Lazy.or_else(same(hh, name), _u => has_item(rest, name))
239	
240	# the names an environment holds, and the file's items and aliases
241	type Names is Data:
242	  Names{items: List<&2, String>, aliases: List<&2, String>}
243	
244	def resolve.local(mm: Maybe<&2, Bind>, +name: String, ns: Names) -> Target:
245	  match mm:
246	    case Some{Bind{n, l, c, k, note}}:
247	      TLocal{l, c}
248	    case None{}:
249	      Names{its, als} = ns
250	      +cs = String.to_list(name)
251	      +head = head_of(cs)
252	      Bool.pick(Target, has_item(its, name), TItem{name},
253	        Lazy.stop(Target, Bool.not(Bool.and(String.contains(name, "."), has(als, head))), TFree{},
254	          _u => TQual{head, rest_of(cs)}))
255	
256	# what a name at a point refers to, given what is in scope
257	def resolve(env: List<&2, Bind>, +name: String, ns: Names) -> Target:
258	  resolve.local(find(env, name), name, ns)
259	
260	# the walk
261	# --------
262	
263	# what the walk has gathered so far, each list reversed
264	type Out is Data:
265	  Out{binds: List<&2, Bind>, uses: List<&2, Use>, scopes: List<&2, Scope>}
266	
267	# what the walk is reading; MLhs and MLhsType carry the environment the
268	# right side of the let will see, and MLhs the kind its names bind with.
269	# MSkip steps over one node (a name a form already bound), then reads on in
270	# next; MStop reads nothing more
271	type Mode is Data:
272	  MBlock{}
273	  MCtors{}
274	  MCtor{}
275	  MHead{}
276	  MName{}
277	  MSig{}
278	  MTele{kind: BindKind}
279	  MTeleType{kind: BindKind}
280	  MLhs{outer: List<&2, Bind>, kind: BindKind}
281	  MLhsType{outer: List<&2, Bind>}
282	  MTerm{}
283	  MSkip{next: Mode}
284	  MStop{}
285	
286	# the walk's result: the environment after, and the output
287	type W is Data:
288	  W{env: List<&2, Bind>, out: Out}
289	
290	# a declaration as written: `+x: List<&2, U32>`, `~f: U32 -> U32`. A space
291	# follows `:` and `,`, spaces surround `->`, everything else is glued
292	def spaced(+tt: String) -> String:
293	  Bool.pick(String, String.eq(tt, "->"), " -> ",
294	    Bool.pick(String, Bool.or(String.eq(tt, ":"), String.eq(tt, ",")), tt ++ " ", tt))
295	
296	# a group's close bracket, "" when it never closed
297	def render_close(close: Maybe<&2, Lex.Tok>) -> String:
298	  match close:
299	    case None{}:
300	      ""
301	    case Some{Lex.Tok{k, t, l, c}}:
302	      t
303	
304	# the text of a whole chain
305	def render_all(nn: Tree.Node) -> String:
306	  match nn:
307	    case Tree.NCons{Tree.Leaf{Lex.Tok{k, t, l, c}}, rest}:
308	      spaced(t) ++ render_all(rest)
309	    case Tree.NCons{Tree.Group{Lex.Tok{k, t, l, c}, kids, close}, rest}:
310	      t ++ render_all(kids) ++ render_close(close) ++ render_all(rest)
311	    case other:
312	      ""
313	
314	# the text of a chain up to its first comma
315	def render(nn: Tree.Node) -> String:
316	  match nn:
317	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TComma{}, t, l, c}}, rest}:
318	      ""
319	    case Tree.NCons{Tree.Leaf{Lex.Tok{k, t, l, c}}, rest}:
320	      spaced(t) ++ render(rest)
321	    case Tree.NCons{Tree.Group{Lex.Tok{k, t, l, c}, kids, close}, rest}:
322	      t ++ render_all(kids) ++ render_close(close) ++ render(rest)
323	    case other:
324	      ""
325	
326	# a use of a name, resolved against the environment
327	def use(+name: String, line: U32, col: U32, +env: List<&2, Bind>, ns: Names, out: Out) -> W:
328	  Out{binds, uses, scopes} = out
329	  W{env, Out{binds, Use{name, line, col, resolve(env, name, ns)} <> uses, scopes}}
330	
331	# the names in scope at a statement's line, recorded
332	def mark(line: U32, +env: List<&2, Bind>, out: Out) -> Out:
333	  Out{binds, uses, scopes} = out
334	  Out{binds, uses, Scope{line, env} <> scopes}
335	
336	# what the names of a telescope bind as, by its bracket: `(` parameters,
337	# `<` type parameters, `{` fields
338	def tele_kind(+oo: String) -> BindKind:
339	  Bool.pick(BindKind, String.eq(oo, "("), KParam{},
340	    Bool.pick(BindKind, String.eq(oo, "<"), KTypeParam{}, KField{}))
341	
342	# a result's environment
343	def env_of(ww: W) -> List<&2, Bind>:
344	  W{env, out} = ww
345	  env
346	
347	# a result's output
348	def out_of(ww: W) -> Out:
349	  W{env, out} = ww
350	  out
351	
352	# the plan of a step
353	# ------------------
354	# The walk takes a node apart only as far as its head (a leaf, a group, a
355	# statement, or anything else), and recurses on the head's parts and on the
356	# rest of the chain. What each step does -- the mode it reads the rest in,
357	# whether it binds or uses a name, which environment it passes on -- is
358	# decided by the plain defs below, from the mode, the head and a peek at the
359	# rest. The forms that need a peek (`K{..}`, `op name`, `x =>`, `@x:`, `&x:`)
360	# read the rest from where they are, and a name the form already bound is
361	# stepped over in MSkip.
362	
363	# does the chain start with a leaf of this kind?
364	def plan.lam(rest: Tree.Node) -> Bool:
365	  match rest:
366	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TLam{}, _t, _l, _c}}, _r}:
367	      True{}
368	    case _other:
369	      False{}
370	
371	# does the chain start with a group?
372	def plan.group(rest: Tree.Node) -> Bool:
373	  match rest:
374	    case Tree.NCons{Tree.Group{_o, _g, _cl}, _r}:
375	      True{}
376	    case _other:
377	      False{}
378	
379	# does the chain start with a name (lower or upper case)?
380	def plan.named(rest: Tree.Node) -> Bool:
381	  match rest:
382	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TName{}, _t, _l, _c}}, _r}:
383	      True{}
384	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TUpper{}, _t, _l, _c}}, _r}:
385	      True{}
386	    case _other:
387	      False{}
388	
389	# does the chain start with a name and a `:`? An upper-case name counts when
390	# upper says so
391	def plan.typed(rest: Tree.Node, upper: Bool) -> Bool:
392	  match rest:
393	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TName{}, _t, _l, _c}},
394	      Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TColon{}, _ct, _cl, _cc}}, _r}}:
395	      True{}
396	    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TUpper{}, _t, _l, _c}},
397	      Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TColon{}, _ct, _cl, _cc}}, _r}}:
398	      upper
399	    case _other:
400	      False{}
401	
402	# the chain's first token; a blank one when it does not start with a leaf
403	def plan.peek(rest: Tree.Node) -> Lex.Tok:
404	  match rest:
405	    case Tree.NCons{Tree.Leaf{tok}, _r}:
406	      tok
407	    case _other:
408	      Lex.Tok{Lex.TSpace{}, "", 0, 0}
409	
410	# the chain after its first node
411	def plan.tail(rest: Tree.Node) -> Tree.Node:
412	  match rest:
413	    case Tree.NCons{_h, r}:
414	      r
415	    case _other:
416	      Tree.NNil{}
417	
418	# the mode the rest is read in after a head that means nothing in this mode
419	def plan.skip(mode: Mode) -> Mode:
420	  match mode:
421	    case MBlock{}:
422	      MStop{}
423	    case MCtors{}:
424	      MStop{}
425	    case MCtor{}:
426	      MSig{}
427	    case MHead{}:
428	      MHead{}
429	    case MName{}:
430	      MSig{}
431	    case MSig{}:
432	      MTerm{}
433	    case MTele{kind}:
434	      MTele{kind}
435	    case MTeleType{kind}:
436	      MTeleType{kind}
437	    case MLhs{outer, kind}:
438	      MLhs{outer, kind}
439	    case MLhsType{outer}:
440	      MLhsType{outer}
441	    case MTerm{}:
442	      MTerm{}
443	    case MSkip{next}:
444	      next
445	    case MStop{}:
446	      MStop{}
447	
448	# the mode the rest is read in after a leaf of kind k
449	def plan.lmode(mode: Mode, kk: Lex.TokKind, +rest: Tree.Node) -> Mode:
450	  match mode kk:
451	    case MHead{} Lex.TKey{}:
452	      MName{}
453	    case MTele{+kind} Lex.TOp{}:
454	      Bool.pick(Mode, plan.named(rest), MSkip{MTele{kind}}, MTele{kind})
455	    case MTele{kind} Lex.TColon{}:
456	      MTeleType{kind}
457	    case MTeleType{kind} Lex.TComma{}:
458	      MTele{kind}
459	    case MTeleType{+kind} Lex.TAll{}:
460	      Bool.pick(Mode, plan.typed(rest, False{}), MSkip{MTeleType{kind}}, MTeleType{kind})
461	    case MLhs{+outer, kind} Lex.TUpper{}:
462	      Bool.pick(Mode, plan.group(rest), MLhs{outer, KPat{}}, MLhs{outer, kind})
463	    case MLhs{+outer, kind} Lex.TDotted{}:
464	      Bool.pick(Mode, plan.group(rest), MLhs{outer, KPat{}}, MLhs{outer, kind})
465	    case MLhs{outer, _kind} Lex.TColon{}:
466	      MLhsType{outer}
467	    case MLhs{_outer, _kind} Lex.TEq{}:
468	      MTerm{}
469	    case MLhs{_outer, _kind} Lex.TBind{}:
470	      MTerm{}
471	    case MLhsType{_outer} Lex.TEq{}:
472	      MTerm{}
473	    case MLhsType{_outer} Lex.TBind{}:
474	      MTerm{}
475	    case MTerm{} Lex.TAll{}:
476	      Bool.pick(Mode, plan.typed(rest, True{}), MSkip{MTerm{}}, MTerm{})
477	    case MTerm{} Lex.TAmp{}:
478	      Bool.pick(Mode, plan.typed(rest, False{}), MSkip{MTerm{}}, MTerm{})
479	    case other _k:
480	      plan.skip(other)
481	
482	# does a leaf of kind k record a binder?
483	def plan.rec(mode: Mode, kk: Lex.TokKind, +rest: Tree.Node) -> Bool:
484	  match mode kk:
485	    case MCtor{} Lex.TUpper{}:
486	      True{}
487	    case MName{} Lex.TName{}:
488	      True{}
489	    case MName{} Lex.TUpper{}:
490	      True{}
491	    case MName{} Lex.TDotted{}:
492	      True{}
493	    case MTele{_kind} Lex.TOp{}:
494	      plan.named(rest)
495	    case MTele{_kind} Lex.TName{}:
496	      True{}
497	    case MTele{_kind} Lex.TUpper{}:
498	      True{}
499	    case MTeleType{_kind} Lex.TAll{}:
500	      plan.typed(rest, False{})
501	    case MLhs{_outer, _kind} Lex.TUpper{}:
502	      Bool.not(plan.group(rest))
503	    case MLhs{_outer, _kind} Lex.TName{}:
504	      True{}
505	    case MTerm{} Lex.TName{}:
506	      plan.lam(rest)
507	    case MTerm{} Lex.TAll{}:
508	      plan.typed(rest, True{})
509	    case MTerm{} Lex.TAmp{}:
510	      plan.typed(rest, False{})
511	    case _other _k:
512	      False{}
513	
514	# does the binder a leaf records go into the environment too? All do but an
515	# item's name and a constructor's, which the file's items hold
516	def plan.push(mode: Mode, kk: Lex.TokKind, rest: Tree.Node) -> Bool:
517	  match mode:
518	    case MCtor{}:
519	      False{}
520	    case MName{}:
521	      False{}
522	    case other:
523	      plan.rec(other, kk, rest)
524	
525	# does a leaf of kind k use a name?
526	def plan.use(mode: Mode, kk: Lex.TokKind, +rest: Tree.Node) -> Bool:
527	  match mode kk:
528	    case MTeleType{_kind} Lex.TName{}:
529	      True{}
530	    case MTeleType{_kind} Lex.TUpper{}:
531	      True{}
532	    case MTeleType{_kind} Lex.TDotted{}:
533	      True{}
534	    case MLhs{_outer, _kind} Lex.TUpper{}:
535	      plan.group(rest)
536	    case MLhs{_outer, _kind} Lex.TDotted{}:
537	      plan.group(rest)
538	    case MLhsType{_outer} Lex.TName{}:
539	      True{}
540	    case MLhsType{_outer} Lex.TUpper{}:
541	      True{}
542	    case MLhsType{_outer} Lex.TDotted{}:
543	      True{}
544	    case MTerm{} Lex.TName{}:
545	      Bool.not(plan.lam(rest))
546	    case MTerm{} Lex.TUpper{}:
547	      True{}
548	    case MTerm{} Lex.TDotted{}:
549	      True{}
550	    case _other _k:
551	      False{}
552	
553	# is a leaf of kind k the `=` or `<-` of a let, whose right side sees the
554	# names outside the let?
555	def plan.keep(mode: Mode, kk: Lex.TokKind) -> Bool:
556	  match mode kk:
557	    case MLhs{_outer, _kind} Lex.TEq{}:
558	      True{}
559	    case MLhs{_outer, _kind} Lex.TBind{}:
560	      True{}
561	    case MLhsType{_outer} Lex.TEq{}:
562	      True{}
563	    case MLhsType{_outer} Lex.TBind{}:
564	      True{}
565	    case _other _k:
566	      False{}
567	
568	# the environment outside a let's left side
569	def plan.outer(mode: Mode) -> List<&2, Bind>:
570	  match mode:
571	    case MLhs{outer, _kind}:
572	      outer
573	    case MLhsType{outer}:
574	      outer
575	    case _other:
576	      []
577	
578	# a binder at the next token, with the note its kind shows
579	def plan.ahead(tok: Lex.Tok, kind: BindKind, +note: String) -> Bind:
580	  match tok:
581	    case Lex.Tok{_k, t, l, c}:
582	      Bind{t, l, c, kind, note}
583	
584	# the name of the next token, "" when there is none
585	def plan.ahead_name(tok: Lex.Tok) -> String:
586	  match tok:
587	    case Lex.Tok{_k, t, _l, _c}:
588	      t
589	
590	# the binder a leaf records: its own name, or for `op name`, `@x:` and `&x:`
591	# the name after it. A telescope's binder notes its declaration
592	def plan.binder(mode: Mode, kk: Lex.TokKind, +tt: String, ll: U32, cc: U32, +rest: Tree.Node) -> Bind:
593	  match mode kk:
594	    case MCtor{} _k:
595	      Bind{tt, ll, cc, KCtor{}, ""}
596	    case MName{} _k:
597	      Bind{tt, ll, cc, KItem{}, ""}
598	    case MTele{kind} Lex.TOp{}:
599	      plan.ahead(plan.peek(rest), kind, tt ++ plan.ahead_name(plan.peek(rest)) ++ render(plan.tail(rest)))
600	    case MTele{kind} _k:
601	      Bind{tt, ll, cc, kind, "" ++ tt ++ render(rest)}
602	    case MTeleType{_kind} _k:
603	      plan.ahead(plan.peek(rest), KTypeVar{}, "")
604	    case MLhs{_outer, kind} _k:
605	      Bind{tt, ll, cc, kind, ""}
606	    case MTerm{} Lex.TName{}:
607	      Bind{tt, ll, cc, KLocal{}, ""}
608	    case MTerm{} _k:
609	      plan.ahead(plan.peek(rest), KTypeVar{}, "")
610	    case _other _k:
611	      Bind{tt, ll, cc, KLocal{}, ""}
612	
613	# a binder onto the environment, when there is one
614	def plan.pushed(push: Bool, +bb: Bind, env: List<&2, Bind>) -> List<&2, Bind>:
615	  match push:
616	    case True{}:
617	      bb <> env
618	    case False{}:
619	      env
620	
621	# a binder onto the output, when there is one
622	def plan.recorded(rec: Bool, +bb: Bind, out: Out) -> Out:
623	  match rec:
624	    case True{}:
625	      Out{binds, uses, scopes} = out
626	      Out{bb <> binds, uses, scopes}
627	    case False{}:
628	      out
629	
630	# a use onto the output, when there is one
631	def plan.used(usd: Bool, +name: String, line: U32, col: U32, env: List<&2, Bind>, ns: Names, out: Out) -> Out:
632	  match usd:
633	    case True{}:
634	      out_of(use(name, line, col, env, ns, out))
635	    case False{}:
636	      out
637	
638	# the environment the rest is read with after a leaf: the one outside a
639	# let's left side at its `=`, else this one with the leaf's binder on it
640	def plan.enter(
641	  keep: Bool,
642	  outer: List<&2, Bind>,
643	  push: Bool,
644	  +bb: Bind,
645	  env: List<&2, Bind>
646	) -> List<&2, Bind>:
647	  match keep:
648	    case True{}:
649	      outer
650	    case False{}:
651	      plan.pushed(push, bb, env)
652	
653	# the mode a group's insides are read in; MStop when they mean nothing here
654	def plan.ginner(mode: Mode, +gt: String) -> Mode:
655	  match mode:
656	    case MSig{}:
657	      MTele{tele_kind(gt)}
658	    case MTeleType{_kind}:
659	      MTerm{}
660	    case MLhs{outer, _kind}:
661	      MLhs{outer, KPat{}}
662	    case MLhsType{_outer}:
663	      MTerm{}
664	    case MTerm{}:
665	      MTerm{}
666	    case _other:
667	      MStop{}
668	
669	# the mode the rest is read in after a group
670	def plan.gnext(mode: Mode) -> Mode:
671	  match mode:
672	    case MSig{}:
673	      MTerm{}
674	    case MLhs{outer, _kind}:
675	      MLhs{outer, KPat{}}
676	    case other:
677	      plan.skip(other)
678	
679	# do the names a group binds stay bound after it? A signature's parameters
680	# and a pattern's binders do
681	def plan.gkeeps(mode: Mode) -> Bool:
682	  match mode:
683	    case MSig{}:
684	      True{}
685	    case MLhs{_outer, _kind}:
686	      True{}
687	    case _other:
688	      False{}
689	
690	# the mode a statement's header is read in
691	def plan.kmode(mode: Mode, sk: Tree.StmtKind, +env: List<&2, Bind>) -> Mode:
692	  match mode sk:
693	    case MBlock{} Tree.SDef{}:
694	      MHead{}
695	    case MBlock{} Tree.SLaw{}:
696	      MHead{}
697	    case MBlock{} Tree.SType{}:
698	      MHead{}
699	    case MBlock{} Tree.SImport{}:
700	      MStop{}
701	    case MBlock{} Tree.SCase{}:
702	      MLhs{env, KPat{}}
703	    case MBlock{} Tree.SFor{}:
704	      MLhs{env, KFor{}}
705	    case MBlock{} Tree.SLet{}:
706	      MLhs{env, KLocal{}}
707	    case MBlock{} Tree.STerm{}:
708	      MTerm{}
709	    case MCtors{} _sk:
710	      MCtor{}
711	    case _other _sk:
712	      MStop{}
713	
714	# the mode a statement's body is read in
715	def plan.bmode(mode: Mode, sk: Tree.StmtKind) -> Mode:
716	  match mode sk:
717	    case MBlock{} Tree.SType{}:
718	      MCtors{}
719	    case MBlock{} Tree.SImport{}:
720	      MStop{}
721	    case MBlock{} _sk:
722	      MBlock{}
723	    case _other _sk:
724	      MStop{}
725	
726	# is the scope recorded before a statement's header?
727	def plan.mark_head(mode: Mode, sk: Tree.StmtKind) -> Bool:
728	  match mode sk:
729	    case MBlock{} Tree.SCase{}:
730	      True{}
731	    case MBlock{} Tree.SFor{}:
732	      True{}
733	    case MBlock{} Tree.SLet{}:
734	      True{}
735	    case MBlock{} Tree.STerm{}:
736	      True{}
737	    case MCtors{} _sk:
738	      True{}
739	    case _other _sk:
740	      False{}
741	
742	# is the scope recorded between a statement's header and its body? A def's is
743	def plan.mark_body(mode: Mode, sk: Tree.StmtKind) -> Bool:
744	  match mode sk:
745	    case MBlock{} Tree.SDef{}:
746	      True{}
747	    case _other _sk:
748	      False{}
749	
750	# the scope recorded onto the output, when it is
751	def plan.marked(yes: Bool, line: U32, +env: List<&2, Bind>, out: Out) -> Out:
752	  match yes:
753	    case True{}:
754	      mark(line, env, out)
755	    case False{}:
756	      out
757	
758	# does a statement close its scope for the statements after it? All but a
759	# let and a `for` in a block do
760	def plan.scoped(mode: Mode, sk: Tree.StmtKind) -> Bool:
761	  match mode sk:
762	    case MBlock{} Tree.SFor{}:
763	      False{}
764	    case MBlock{} Tree.SLet{}:
765	      False{}
766	    case _other _sk:
767	      True{}
768	
769	# the mode the statements after a statement are read in
770	def plan.snext(mode: Mode) -> Mode:
771	  match mode:
772	    case MBlock{}:
773	      MBlock{}
774	    case MCtors{}:
775	      MCtors{}
776	    case other:
777	      plan.skip(other)
778	
779	# the walk: one node in one mode, against an environment. It takes the node
780	# apart as far as its head, and the plan above says what the head does in
781	# this mode. Every recursive call is on a subtree (kids, body, gkids or
782	# rest), never on n itself
783	def walk(nn: Tree.Node, +mode: Mode, +env: List<&2, Bind>, +ns: Names, out: Out) -> W:
784	  match nn:
785	    case Tree.NCons{hd, +rest}:
786	      match hd:
787	        case Tree.Leaf{Lex.Tok{+k, +t, +l, +c}}:
788	          +keep = plan.keep(mode, k)
789	          +bb = plan.binder(mode, k, t, l, c, rest)
790	          +o1 = plan.recorded(plan.rec(mode, k, rest), bb, out)
791	          +o2 = plan.used(plan.use(mode, k, rest), t, l, c, env, ns, o1)
792	          +e2 = plan.enter(keep, plan.outer(mode), plan.push(mode, k, rest), bb, env)
793	          +r = walk(rest, plan.lmode(mode, k, rest), e2, ns, o2)
794	          W{Bool.pick(List<&2, Bind>, keep, env, env_of(r)), out_of(r)}
795	        case Tree.Group{Lex.Tok{_gk, gt, _gl, _gc}, gkids, _close}:
796	          +g = walk(gkids, plan.ginner(mode, gt), env, ns, out)
797	          walk(rest, plan.gnext(mode), Bool.pick(List<&2, Bind>, plan.gkeeps(mode), env_of(g), env), ns, out_of(g))
798	        case Tree.Stmt{+sk, +kids, body}:
799	          +h = walk(kids, plan.kmode(mode, sk, env), env, ns,
800	            plan.marked(plan.mark_head(mode, sk), Tree.line(kids), env, out))
801	          +b = walk(body, plan.bmode(mode, sk), env_of(h), ns,
802	            plan.marked(plan.mark_body(mode, sk), Tree.line(kids), env_of(h), out_of(h)))
803	          walk(rest, plan.snext(mode), Bool.pick(List<&2, Bind>, plan.scoped(mode, sk), env, env_of(h)), ns, out_of(b))
804	        case _other:
805	          walk(rest, plan.skip(mode), env, ns, out)
806	    case _other:
807	      W{env, out}
808	
809	# notes
810	# -----
811	
812	# leading spaces dropped
813	def lstrip(cs: List<&2, Char>) -> List<&2, Char>:
814	  match cs:
815	    case Con{' ', t}:
816	      lstrip(t)
817	    case other:
818	      other
819	
820	# a line's text without its indentation
821	def stripped(+text: String) -> String:
822	  String.from_list(lstrip(String.to_list(text)))
823	
824	# a declaration carries its own note; anything else shows the line that
825	# bound it, which `text` gives only when it is asked for
826	def note_for(kind: BindKind, +note: String, text: Unit -> String) -> String:
827	  match kind:
828	    case KParam{}:
829	      note
830	    case KField{}:
831	      note
832	    case KTypeParam{}:
833	      note
834	    case other:
835	      text(Unit{})
836	
837	# the lines from line `line` on, given the lines from line `at` on: a step
838	# forward from where the last binder was, not a walk from the first line
839	def annotate.ahead(+line: U32, +at: U32, cur: List<&2, String>) -> List<&2, String>:
840	  List.drop(&2, String, cur, U32.to_nat(U32.sub(line, at)))
841	
842	# the first line of these, or ""
843	def annotate.head(+cur: List<&2, String>) -> String:
844	  Maybe.default(&2, String, List.head(&2, String, cur), "")
845	
846	# a line read from the first, for a binder behind the last one
847	def annotate.back(lines: List<&2, String>, +line: U32) -> String:
848	  Maybe.default(&2, String, List.get(&2, String, lines, U32.to_nat(line)), "")
849	
850	# every binder with its note filled. Binders come in source order, so the
851	# lines are read once, front to back, from where the last binder was (`cur`
852	# holds the lines from line `at` on); a binder behind that point reads its
853	# line from the start
854	def annotate.go(binds: List<&2, Bind>, +lines: List<&2, String>, +at: U32, +cur: List<&2, String>) -> List<&2, Bind>:
855	  match binds:
856	    case Nil{}:
857	      Nil{}
858	    case Con{Bind{name, +line, col, +kind, note}, rest}:
859	      +ahead = U32.is_ge(line, at)
860	      +here = Lazy.either(List<&2, String>, ahead, _u => annotate.ahead(line, at, cur), _v => cur)
861	      +text = Lazy.either(String, ahead, _u => annotate.head(here), _v => annotate.back(lines, line))
862	      Bind{name, line, col, kind, note_for(kind, note, _w => stripped(text))}
863	        <> annotate.go(rest, lines, Bool.pick(U32, ahead, line, at), here)
864	
865	# every binder with its note filled
866	def annotate(binds: List<&2, Bind>, +lines: List<&2, String>) -> List<&2, Bind>:
867	  annotate.go(binds, lines, 0, lines)
868	
869	# putting it together
870	# -------------------
871	
872	# the gathered output, in source order and annotated
873	def finish(oo: Out, lines: List<&2, String>) -> Bound:
874	  Out{binds, uses, scopes} = oo
875	  Bound{annotate(List.reverse(&2, Bind, binds), lines), List.reverse(&2, Use, uses), List.reverse(&2, Scope, scopes)}
876	
877	# the binding structure of a parsed source
878	def of_tree(+root: Tree.Node, lines: List<&2, String>) -> Bound:
879	  finish(out_of(walk(root, MBlock{}, [], Names{items(root, []), aliases(root, [])}, Out{[], [], []})), lines)
880	
881	# the binding structure of a source
882	def bound(+source: String) -> Bound:
883	  of_tree(Tree.parse(source), String.lines(source))
884	
885	# queries
886	# -------
887	
888	# where a name is: a binder, or a use of one
889	type Site is Data:
890	  SBind{bind: Bind}
891	  SUse{use: Use}
892	
893	# does the name at (l, c) cover the position (line, col)?
894	def covers(+l2: U32, +c2: U32, +name: String, +line: U32, +col: U32) -> Bool:
895	  +end = (c2 + U32.from_nat(String.length(name)) : U32)
896	  Bool.and(U32.is_eq(l2, line), Bool.and(U32.is_le(c2, col), U32.is_lt(col, end)))
897	
898	# the binder whose name covers a position
899	def bind_at(binds: List<&2, Bind>, +line: U32, +col: U32) -> Maybe<&2, Site>:
900	  match binds:
901	    case Nil{}:
902	      None{}
903	    case Con{Bind{+name, +l, +c, kind, note}, rest}:
904	      +more = bind_at(rest, line, col)
905	      Bool.pick(Maybe<&2, Site>, covers(l, c, name, line, col), Some{SBind{Bind{name, l, c, kind, note}}}, more)
906	
907	# the use whose name covers a position
908	def use_at(uses: List<&2, Use>, +line: U32, +col: U32) -> Maybe<&2, Site>:
909	  match uses:
910	    case Nil{}:
911	      None{}
912	    case Con{Use{+name, +l, +c, tg}, rest}:
913	      +more = use_at(rest, line, col)
914	      Bool.pick(Maybe<&2, Site>, covers(l, c, name, line, col), Some{SUse{Use{name, l, c, tg}}}, more)
915	
916	def at.or(mm: Maybe<&2, Site>, uses: List<&2, Use>, line: U32, col: U32) -> Maybe<&2, Site>:
917	  match mm:
918	    case Some{site}:
919	      Some{site}
920	    case None{}:
921	      use_at(uses, line, col)
922	
923	# the site at a position
924	def at(bb: Bound, +line: U32, +col: U32) -> Maybe<&2, Site>:
925	  Bound{binds, uses, scopes} = bb
926	  at.or(bind_at(binds, line, col), uses, line, col)
927	
928	# the binder at a position (a use's target, or the binder itself)
929	def binder(binds: List<&2, Bind>, +line: U32, +col: U32) -> Maybe<&2, Bind>:
930	  match binds:
931	    case Nil{}:
932	      None{}
933	    case Con{Bind{name, +l, +c, kind, note}, rest}:
934	      +more = binder(rest, line, col)
935	      +here = Bool.and(U32.is_eq(l, line), U32.is_eq(c, col))
936	      Bool.pick(Maybe<&2, Bind>, here, Some{Bind{name, l, c, kind, note}}, more)
937	
938	# the names in scope at a line: those of the statement on it, else of the
939	# nearest statement above
940	def visible.go(scopes: List<&2, Scope>, +qline: U32, best: List<&2, Bind>) -> List<&2, Bind>:
941	  match scopes:
942	    case Nil{}:
943	      best
944	    case Con{Scope{+line, env}, rest}:
945	      +hit = U32.is_le(line, qline)
946	      visible.go(rest, qline, Bool.pick(List<&2, Bind>, hit, env, best))
947	
948	# the scopes hold binders before their notes were filled: read each back
949	def noted(mm: Maybe<&2, Bind>, bb: Bind) -> Bind:
950	  match mm:
951	    case None{}:
952	      bb
953	    case Some{full}:
954	      full
955	
956	# does (l1, c1) come before (l2, c2) in the source?
957	def before(+l1: U32, +c1: U32, +l2: U32, +c2: U32) -> Bool:
958	  Bool.or(U32.is_lt(l1, l2), Bool.and(U32.is_eq(l1, l2), U32.is_lt(c1, c2)))
959	
960	# does a cursor's head sit at or after a position (the seek stops there)?
961	def seek.stop(cur: List<&2, Bind>, +line: U32, +col: U32) -> Bool:
962	  match cur:
963	    case Nil{}:
964	      True{}
965	    case Con{Bind{name, +l, +c, kind, note}, rest}:
966	      Bool.not(before(l, c, line, col))
967	
968	# the binders from the first one not before a position on; the binders are in
969	# source order, so none this drops sits at the position. stop is seek.stop of
970	# binds, carried so the step stays a loop
971	def seek(binds: List<&2, Bind>, +line: U32, +col: U32, +stop: Bool) -> List<&2, Bind>:
972	  match binds:
973	    case Nil{}:
974	      Nil{}
975	    case Con{h, +rest}:
976	      match stop:
977	        case True{}:
978	          h <> rest
979	        case False{}:
980	          seek(rest, line, col, seek.stop(rest, line, col))
981	
982	# the binder at the head of a cursor, when it sits at the position
983	def seek.head(cur: List<&2, Bind>, +line: U32, +col: U32) -> Maybe<&2, Bind>:
984	  match cur:
985	    case Nil{}:
986	      None{}
987	    case Con{Bind{name, +l, +c, kind, note}, rest}:
988	      Bool.pick(Maybe<&2, Bind>, Bool.and(U32.is_eq(l, line), U32.is_eq(c, col)), Some{Bind{name, l, c, kind, note}},
989	        None{})
990	
991	# each binder of an environment, outermost first, with the note its annotated
992	# twin carries, pushed onto acc (so acc ends innermost first again). cur is a
993	# cursor into binds that drops only binders before (tl, tc), the last one
994	# read: an environment's binders were pushed in source order, so each lookup
995	# picks up where the last stopped and binds is read once, not once per
996	# binder. A binder before the last one read starts the cursor over
997	def refresh.go(
998	  env: List<&2, Bind>,
999	  +binds: List<&2, Bind>,
1000	  +cur: List<&2, Bind>,
1001	  +tl: U32,
1002	  +tc: U32,
1003	  acc: List<&2, Bind>
1004	) -> List<&2, Bind>:
1005	  match env:
1006	    case Nil{}:
1007	      acc
1008	    case Con{Bind{name, +l, +c, kind, note}, rest}:
1009	      +start = Bool.pick(List<&2, Bind>, before(l, c, tl, tc), binds, cur)
1010	      +from = seek(start, l, c, seek.stop(start, l, c))
1011	      refresh.go(rest, binds, from, l, c, noted(seek.head(from, l, c), Bind{name, l, c, kind, note}) <> acc)
1012	
1013	# each binder of an environment, with the note its annotated twin carries
1014	def refresh(env: List<&2, Bind>, +binds: List<&2, Bind>) -> List<&2, Bind>:
1015	  refresh.go(List.reverse(&2, Bind, env), binds, binds, 0, 0, [])
1016	
1017	# the names in scope at a line: those of the statement on it, else of the
1018	# nearest statement above
1019	def visible(bb: Bound, qline: U32) -> List<&2, Bind>:
1020	  Bound{binds, uses, scopes} = bb
1021	  refresh(visible.go(scopes, qline, []), binds)
1022	
1023	# every position a binder is named at: its own, then its uses'
1024	def sites.go(uses: List<&2, Use>, +line: U32, +col: U32) -> List<&2, Pos>:
1025	  match uses:
1026	    case Nil{}:
1027	      Nil{}
1028	    case Con{Use{name, l, c, TLocal{+tl, +tc}}, rest}:
1029	      +more = sites.go(rest, line, col)
1030	      Bool.pick(List<&2, Pos>, Bool.and(U32.is_eq(tl, line), U32.is_eq(tc, col)), Pos{l, c} <> more, more)
1031	    case Con{other, rest}:
1032	      sites.go(rest, line, col)
1033	
1034	# every position a binder is named at: its own, then its uses'
1035	def sites(bb: Bound, +line: U32, +col: U32) -> List<&2, Pos>:
1036	  Bound{binds, uses, scopes} = bb
1037	  Pos{line, col} <> sites.go(uses, line, col)
1038	
1039	# every position an item of the file is named at: its declaration, then its
1040	# uses
1041	def item_sites.binds(binds: List<&2, Bind>, +name: String) -> List<&2, Pos>:
1042	  match binds:
1043	    case Nil{}:
1044	      Nil{}
1045	    case Con{Bind{+n, l, c, KItem{}, note}, rest}:
1046	      +more = item_sites.binds(rest, name)
1047	      Bool.pick(List<&2, Pos>, String.eq(n, name), Pos{l, c} <> more, more)
1048	    case Con{Bind{+n, l, c, KCtor{}, note}, rest}:
1049	      +more = item_sites.binds(rest, name)
1050	      Bool.pick(List<&2, Pos>, String.eq(n, name), Pos{l, c} <> more, more)
1051	    case Con{other, rest}:
1052	      item_sites.binds(rest, name)
1053	
1054	def item_sites.uses(uses: List<&2, Use>, +name: String) -> List<&2, Pos>:
1055	  match uses:
1056	    case Nil{}:
1057	      Nil{}
1058	    case Con{Use{n, l, c, TItem{+t}}, rest}:
1059	      +more = item_sites.uses(rest, name)
1060	      Bool.pick(List<&2, Pos>, String.eq(t, name), Pos{l, c} <> more, more)
1061	    case Con{other, rest}:
1062	      item_sites.uses(rest, name)
1063	
1064	# every position an item of the file is named at: its declaration, then its
1065	# uses
1066	def item_sites(bb: Bound, +name: String) -> List<&2, Pos>:
1067	  Bound{binds, uses, scopes} = bb
1068	  List.append(&2, Pos, item_sites.binds(binds, name), item_sites.uses(uses, name))
1069	
1070	# every position a name not of this file is used at (Base, or through an
1071	# alias)
1072	def named_sites.go(uses: List<&2, Use>, +name: String) -> List<&2, Pos>:
1073	  match uses:
1074	    case Nil{}:
1075	      Nil{}
1076	    case Con{Use{+n, l, c, TLocal{tl, tc}}, rest}:
1077	      named_sites.go(rest, name)
1078	    case Con{Use{+n, l, c, tg}, rest}:
1079	      +more = named_sites.go(rest, name)
1080	      Bool.pick(List<&2, Pos>, String.eq(n, name), Pos{l, c} <> more, more)
1081	
1082	# every position a name not of this file is used at (Base, or through an
1083	# alias)
1084	def named_sites(bb: Bound, +name: String) -> List<&2, Pos>:
1085	  Bound{binds, uses, scopes} = bb
1086	  named_sites.go(uses, name)