use bind for nullary functions

grammar/conflicts.js

@@ -58,9 +58,9 @@ module.exports = {
      */
 
     // Function vs bind vs splice
-    [$._fun_name, $.pat_name],
-    [$._fun_name, $.exp_name],
-    [$._fun_name, $.exp_name, $.pat_name],
+    [$._function_name, $.pat_name],
+    [$._function_name, $.exp_name],
+    [$._function_name, $.exp_name, $.pat_name],
 
     // Signature vs bind
     [$.signature, $.pat_name],

grammar/context.js

@@ -47,7 +47,7 @@ module.exports = {
   )),
 
   implicit_param: $ => prec.left('implicit', seq(
-    $.implicit_parid,
+    $.implicit_variable,
     $._type_annotation,
   )),
 

grammar/decl.js

@@ -60,94 +60,57 @@ module.exports = {
 
   guard_equation: $ => seq($._guards, '=', $._cmd_texp_end, field('expression', $._exp)),
 
-  _fun_guards: $ => repeat1($.guard_equation),
+  _bind_guards: $ => repeat1($.guard_equation),
 
-  _funrhs: $ => seq(
+  _bind_match: $ => seq(
     choice(
       seq('=', field('expression', $._exp)),
-      $._fun_guards,
+      $._bind_guards,
     ),
     optional($._where_binds),
   ),
 
-  /**
-    * The `implicit_parid` here is for:
-    * g = let ?par = Impy 5 in f
-    */
-  _fun_name: $ => choice($._var, $.implicit_parid),
+  _function_name: $ => field('name', $._var),
 
-  _funvar: $ => seq(
-    field('name', $._fun_name),
-    optional(field('patterns', $.patterns)),
+  function_head_parens: $ => parens(
+    $,
+    choice(
+      $._function_head,
+      $._function_head_patterns,
+    ),
   ),
 
-  _funlhs_parens: $ => choice(
-    $._funvar,
-    $._funlhs_common,
+  _function_head_patterns: $ => choice(
+    $._function_name,
+    $.function_head_parens,
   ),
 
-  /**
-   * Patterns following a parenthesized pattern are always optional for simplicity, even though GHC requires them for
-   * the outermost set.
-   */
-  _funlhs_common: $ => choice(
+  _function_head: $ => choice(
+    seq($._function_head_patterns, field('patterns', $.patterns)),
     alias($._funlhs_infix, $.infix),
-    seq(
-      parens($, $._funlhs_parens),
-      optional(field('patterns', $.patterns)),
-    ),
   ),
 
-  _funlhs: $ => choice(
-    seq(
-      field('name', $._fun_name),
-      field('patterns', $.patterns),
-    ),
-    $._funlhs_common,
+  function: $ => seq(
+    $._function_head,
+    $._bind_match,
   ),
 
   /**
-   * This little contortion ensures that a nullary function declaration/variable binding is not considered for a dynamic
-   * conflict:
-   *
-   * > fun = exp
-   *
-   * vs.
-   *
-   * > fun a b c = exp
-   * > Con a b c = exp
-   *
-   * This works by creating a shift/reduce conflict between `function` and `bind`.
-   * The shift step is from `_var` to `_funrhs` (the latter of which starts with either `=` or `|`, so lookahead is
-   * clear-cut) and the reduce step is from `_var` to `pat_name`.
-   * The shift precedence is set by giving _both_ nodes the prec 'function-nullary', and the reduce precedence is set by
-   * giving `_var` in `pat_name` the prec 'pat-name'.
-   * An entry in the `precedences` config in `grammar.js` defines the order of these precedences, causing the parser to
-   * create only a state transition to `_funrhs` when encountering a `=` or `|` after a `variable`.
-   */
-  function: $ => choice(
-    prec('function-nullary', seq(
-      field('name', choice($._var, $.implicit_parid)),
-      $._funrhs,
-    )),
-    seq(
-      $._funlhs,
-      $._funrhs,
-    ),
-  ),
-
-  bind: $ => seq(
-    field('pattern', $._pat),
-    $._funrhs,
-  ),
+    * The `implicit_variable` here is for:
+    * g = let ?par = Impy 5 in f
+    */
+  bind: $ => prec('bind', seq(
+    choice(field('pattern', $._pat), field('name', $._var), field('implicit', $.implicit_variable)),
+    $._bind_match,
+  )),
 
   /**
-  * The difference between a `function` with a `_funlhs_infix` and a `bind` is that the former is for _declaring_ a
-  * `varop` and the latter uses a `conop` to pattern match on the rhs expression.
+  * The difference between a `function` with a `_funlhs_infix` and a `bind` with `pat_infix` is that the former is for
+  * _declaring_ a `varop` and the latter uses a `conop` to pattern match on the rhs expression.
   * The former may not have a type annotation, while the latter may.
   *
-  * > h : t :: [Int] = undefined
   * > a <> b = undefined
+  * > h : t :: [Int] = undefined
   */
   _decl: $ => choice(
     $._gendecl,

grammar/exp.js

@@ -257,7 +257,7 @@ module.exports = {
   exp_name: $ => choice(
     $._cons,
     $._vars,
-    $.implicit_parid,
+    $.implicit_variable,
     $.label,
   ),
 

grammar/inline.js

@@ -74,9 +74,8 @@ module.exports = {
     // function vs bind
     // ------------------------------------------------
 
-    $._funlhs,
-    $._funlhs_parens,
-    $._funvar,
+    $._function_head_patterns,
+    $._function_head,
 
   ],
 

grammar/lexeme.js

@@ -10,7 +10,7 @@ module.exports = {
 
   _varid: _ => token(seq(varid_start_char, id_char, /#*/)),
 
-  implicit_parid: _ => token(seq('?', varid_start_char, id_char)),
+  implicit_variable: _ => token(seq('?', varid_start_char, id_char)),
 
   _conid: _ => token(seq(conid_start_char, id_char, /#*/)),
 

grammar/precedences.js

@@ -66,7 +66,7 @@ module.exports = {
     // ------------------------------------------------
 
     [
-      'function-nullary',
+      'bind',
       'pat-name',
     ],