feat(grammar): add closures

grammar.js

@@ -13,6 +13,7 @@ const PREC = {
   and: 3,
   or: 2,
   assign: 0,
+  closure: -1,
 };
 const TOKEN_TREE_NON_SPECIAL_PUNCTUATION = [
   '+',
@@ -589,7 +590,7 @@ module.exports = grammar({
         '_',
       ),
     // for example in let (a, b) = c; it would be `(a, b)`
-    tuple_pattern: ($) => seq('(', sepBy(',', $._pattern), optional(','), ')'),
+    tuple_pattern: ($) => seq('(', sepBy(',', choice($._pattern, $.closure_expression)), optional(','), ')'),
 
     // for example in let [a, b] = c; it would be `[a, b]`
     slice_pattern: ($) => seq('[', sepBy(',', $._pattern), optional(','), ']'),
@@ -806,6 +807,7 @@ module.exports = grammar({
         $.index_expression,
         $.parenthesized_expression,
         prec(1, $.macro_invocation),
+        $.closure_expression,
       ),
     // for example in a::<A>(); it would be `a::<A>`
     generic_function: ($) =>
@@ -1035,6 +1037,29 @@ module.exports = grammar({
     while_expression: ($) =>
       seq('while', field('condition', $._condition), field('body', $.block)),
 
+    // |x| { x + 1}
+    closure_expression: $ => prec(PREC.closure, seq(
+      optional('move'),
+      field('parameters', $.closure_parameters),
+      choice(
+        seq(
+          optional(seq('->', field('return_type', $._type))),
+          field('body', $.block),
+        ),
+        field('body', choice($.expression, '_')),
+      ),
+    )),
+
+    closure_parameters: $ => seq(
+      '|',
+      sepBy(',', choice(
+        $._pattern,
+        $.parameter,
+      )),
+      '|',
+    ),
+
+    // for x in a.iter()
     for_expression: $ => seq(
       'for',
       field('pattern', $._pattern),

package.json

@@ -52,6 +52,7 @@
     "build": "tree-sitter generate --no-bindings",
     "build-wasm": "tree-sitter build --wasm",
     "lint": "eslint grammar.js",
+    "fix": "eslint grammar.js --fix",
     "parse": "tree-sitter parse",
     "test": "tree-sitter test"
   },
@@ -103,4 +104,4 @@
       ]
     }
   }
-}
+}

queries/highlights.scm

@@ -71,6 +71,8 @@
     "<"
     ">"
   ] @punctuation.bracket)
+(closure_parameters
+  "|" @punctuation.bracket)
 
 ; ---
 ; Variables
@@ -92,6 +94,8 @@
 (parameter
 	pattern: (identifier) @variable.parameter)
 
+(closure_parameters
+	(identifier) @variable.parameter)
 ; -------
 ; Keywords
 ; -------

queries/indents.scm

@@ -115,6 +115,16 @@
   (#not-same-line? @expr-start @pattern-guard)
 ) @indent
 
+; Align closure parameters if they span more than one line
+(closure_parameters
+  "|"
+  .
+  (_) @anchor
+  (_) @expr-end
+  .
+  (#not-same-line? @anchor @expr-end)
+) @align
+
 (for_expression
   "in" @in
   .

queries/locals.scm

@@ -7,6 +7,7 @@
   (type_item)
   (trait_item)
   (impl_item)
+  (closure_expression)
   (block)
 ] @local.scope
 
@@ -20,6 +21,8 @@
 (constrained_type_parameter
   left: (type_identifier) @local.definition)
 
+(closure_parameters (identifier) @local.definition)
+
 ; References
 (identifier) @local.reference
 (type_identifier) @local.reference

queries/textobjects.scm

@@ -1,6 +1,9 @@
 (function_item
   body: (_) @function.inside) @function.around
 
+(closure_expression
+  body: (_) @function.inside) @function.around
+
 (struct_item
   body: (_) @class.inside) @class.around
 
@@ -16,6 +19,9 @@
 (parameters 
   ((_) @parameter.inside . ","? @parameter.around) @parameter.around)
 
+(closure_parameters
+  ((_) @parameter.inside . ","? @parameter.around) @parameter.around)
+
 (type_parameters
   ((_) @parameter.inside . ","? @parameter.around) @parameter.around)