wip(#218): Rust-like record syntax — grammar + token bridges + 6 fixtures

ATOMIC PR IN PROGRESS — DO NOT MERGE (15/257 still failing).

Contains:
- Grammar: bare { = block, records #{ } (token.ml/lexer.ml/parser.mly,
  from stage-c/pc-brace-disambig). Conflicts 72->68 S/R, 10->7 R/R.
- Token-bridge completeness: added HASH_LBRACE arm to BOTH
  lib/parse.ml AND lib/parse_driver.ml (same non-exhaustive-match
  class as #219 EXTERN — warning-8 demoted, Match_failure at runtime;
  these were the ONLY two Token->Parser bridges).
- Migrated 6 regression .affine fixtures (expression-position record
  literals {..}->#{..}; type-position records unchanged).

Progress: 21 -> 15 failures. Remaining 15 are inline AffineScript
source embedded as string literals in the OCaml test suite (E2E TEA
counter/titlescreen, LSP Phase B hover, full_pipeline, AOT test 17,
etc.) — those test inputs still use old record syntax and need #{
migration in the test .ml fixtures, not .affine files.

Refs #218

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

conformance/valid/011_rows.affine

@@ -9,7 +9,7 @@ fn get_name[..r](entity: {name: String, ..r}) -> String {
 }
 
 fn with_id[..r](record: {..r}, id: Int) -> {id: Int, ..r} {
-  { id: id, ..record }
+  #{ id: id, ..record }
 }
 
 type HasPosition[..r] = {x: Int, y: Int, ..r}

examples/rows.affine

@@ -15,5 +15,5 @@ struct Point3D {
 fn getX(p: Point2D) -> Int = p.x;
 
 fn mk_point(x: Int, y: Int) -> Point2D {
-  { x: x, y: y }
+  #{ x: x, y: y }
 }

examples/typecheck_complete_test.affine

@@ -15,11 +15,11 @@ enum Color {
 }
 
 fn make_point(x: Int, y: Int) -> Point {
-  { x: x, y: y }
+  #{ x: x, y: y }
 }
 
 fn origin() -> Point {
-  { x: 0, y: 0 }
+  #{ x: 0, y: 0 }
 }
 
 fn mutate_counter() -> Int {

lib/lexer.ml

@@ -165,6 +165,9 @@ let rec token state buf =
   | "->" -> ARROW
   | "=>" -> FAT_ARROW
   | "::" -> COLONCOLON
+  (* Record-literal opener (affinescript#215): `#{` is the unambiguous
+     record/struct-literal sigil; bare `{` is always a block. *)
+  | "#{" -> HASH_LBRACE
   (* Row variable "..name" — must come before ".." so sedlex prefers the longer match *)
   | "..", lower_ident ->
     let s = Sedlexing.Utf8.lexeme buf in

lib/parse.ml

@@ -105,6 +105,7 @@ let next_token state () =
     | Token.LPAREN -> Parser.LPAREN
     | Token.RPAREN -> Parser.RPAREN
     | Token.LBRACE -> Parser.LBRACE
+    | Token.HASH_LBRACE -> Parser.HASH_LBRACE
     | Token.RBRACE -> Parser.RBRACE
     | Token.LBRACKET -> Parser.LBRACKET
     | Token.RBRACKET -> Parser.RBRACKET

lib/parse_driver.ml

@@ -76,6 +76,7 @@ let to_menhir_token (tok : Token.t) : Parser.token =
     | Token.LPAREN -> Parser.LPAREN
     | Token.RPAREN -> Parser.RPAREN
     | Token.LBRACE -> Parser.LBRACE
+    | Token.HASH_LBRACE -> Parser.HASH_LBRACE
     | Token.RBRACE -> Parser.RBRACE
     | Token.LBRACKET -> Parser.LBRACKET
     | Token.RBRACKET -> Parser.RBRACKET

lib/parser.mly

@@ -66,6 +66,7 @@ let rec effect_union_of_list = function
 
 /* Punctuation */
 %token LPAREN RPAREN LBRACE RBRACE LBRACKET RBRACKET
+%token HASH_LBRACE   /* `#{` record-literal opener (affinescript#215) */
 %token COMMA SEMICOLON COLON COLONCOLON DOT DOTDOT
 %token ARROW FAT_ARROW PIPE AT UNDERSCORE BACKSLASH QUESTION
 
@@ -768,10 +769,11 @@ expr_primary:
      ordinary parameter binding named "self". */
   | SELF_KW { ExprVar (mk_ident "self" $startpos $endpos) }
   | name = lower_ident { ExprVar (mk_ident name $startpos $endpos) }
-  /* Struct literal: `Point { x: v, y: w }`.  Must come before the plain
-     upper_ident production so Menhir shifts LBRACE rather than reducing
-     upper_ident to ExprVar when the next token is LBRACE. */
-  | _ty = upper_ident LBRACE b = expr_record_body RBRACE
+  /* Struct literal: `Point #{ x: v, y: w }` (affinescript#215). The `#{`
+     sigil makes this unambiguous against a bare block and removes the
+     Rust-style struct-literal-in-`if`/`match`-scrutinee hazard entirely;
+     no production-ordering hack needed any more. */
+  | _ty = upper_ident HASH_LBRACE b = expr_record_body RBRACE
     { ExprRecord { er_fields = fst b; er_spread = snd b } }
   | name = upper_ident { ExprVar (mk_ident name $startpos $endpos) }
   | ty = upper_ident COLONCOLON variant = upper_ident
@@ -787,11 +789,12 @@ expr_primary:
   /* Arrays */
   | LBRACKET es = separated_list(COMMA, expr) RBRACKET { ExprArray es }
 
-  /* Records — use a recursive rule (expr_record_body / expr_record_rest) to
-     avoid the LALR(1) greedy-separator conflict that arises when a ROW_VAR
-     spread like `..record` follows a COMMA that `separated_list` has already
-     consumed expecting another record_field. */
-  | LBRACE b = expr_record_body RBRACE
+  /* Anonymous record `#{ f: v, ..spread }` (affinescript#215). The `#{`
+     sigil removes the entire block-vs-record-literal ambiguity (family
+     C+D) by construction — bare `{` is now unconditionally a block.
+     expr_record_body / expr_record_rest stay recursive to avoid the
+     ROW_VAR greedy-separator conflict on `..spread` after a COMMA. */
+  | HASH_LBRACE b = expr_record_body RBRACE
     { ExprRecord { er_fields = fst b; er_spread = snd b } }
 
   /* Block */

lib/token.ml

@@ -73,6 +73,7 @@ type t =
   | RPAREN
   | LBRACE
   | RBRACE
+  | HASH_LBRACE   (** #{ — record-literal opener (affinescript#215) *)
   | LBRACKET
   | RBRACKET
   | COMMA
@@ -187,6 +188,7 @@ let to_string = function
   | RPAREN -> ")"
   | LBRACE -> "{"
   | RBRACE -> "}"
+  | HASH_LBRACE -> "#{"
   | LBRACKET -> "["
   | RBRACKET -> "]"
   | COMMA -> ","

test/e2e/fixtures/row_polymorphism.affine

@@ -16,5 +16,5 @@ struct Point3D {
 fn getX(p: Point2D) -> Int = p.x;
 
 fn mk_point(x: Int, y: Int) -> Point2D {
-  { x: x, y: y }
+  #{ x: x, y: y }
 }

test/e2e/fixtures/type_decls.affine

@@ -27,9 +27,9 @@ enum Result[T, E] {
 }
 
 fn make_point(x: Int, y: Int) -> Point {
-  { x: x, y: y }
+  #{ x: x, y: y }
 }
 
 fn origin() -> Point {
-  { x: 0, y: 0 }
+  #{ x: 0, y: 0 }
 }