Allow 'as' keyword in binary pattern match expressions

grammar.js

@@ -613,7 +613,10 @@ module.exports = grammar({
         alias($._pattern_binary_expression, $.binary_expression)
       ),
     _pattern_binary_expression: ($) =>
-      binaryExpr(prec.left, 1, "<>", $._pattern_expression),
+      choice(
+        binaryExpr(prec.left, 1, "<>", $._pattern_expression),
+        binaryExpr(prec.left, 1, "as", $.string, $.identifier)
+      ),
     _pattern: ($) =>
       seq(
         $._pattern_expression,
@@ -859,9 +862,13 @@ function series_of(rule, separator) {
 
 // A binary expression with a left-hand side, infix operator, and then right-hand-side
 // https://github.com/elixir-lang/tree-sitter-elixir/blob/de20391afe5cb03ef1e8a8e43167e7b58cc52869/grammar.js#L850-L859
-function binaryExpr(assoc, precedence, operator, expr) {
+function binaryExpr(assoc, precedence, operator, left, right = null) {
   return assoc(
     precedence,
-    seq(field("left", expr), field("operator", operator), field("right", expr))
+    seq(
+      field("left", left),
+      field("operator", operator),
+      field("right", right || left)
+    )
   );
 }

test/corpus/cases.txt

@@ -108,3 +108,81 @@ pub fn listed(names: List(String), person: Person) -> String {
                 (list_pattern)))
             (record
               (constructor_name))))))))
+
+================================================================================
+Pattern matching binaries with 'as'
+================================================================================
+
+// From https://gleam.run/news/v0.31-keeping-dependencies-explicit/#quality-of-life-improvements
+case tag {
+  "category " as key <> value
+  | "region " as key <> value
+  | "priority " as key <> value -> {
+    let key = string.trim(key)
+    Ok(Tag(key, value))
+  }
+  _ -> Error(Nil)
+}
+
+--------------------------------------------------------------------------------
+
+(source_file
+  (comment)
+  (case
+    (case_subjects
+      (identifier))
+    (case_clauses
+      (case_clause
+        (case_clause_patterns
+          (case_clause_pattern
+            (binary_expression
+              (binary_expression
+                (string
+                  (quoted_content))
+                (identifier))
+              (identifier)))
+          (case_clause_pattern
+            (binary_expression
+              (binary_expression
+                (string
+                  (quoted_content))
+                (identifier))
+              (identifier)))
+          (case_clause_pattern
+            (binary_expression
+              (binary_expression
+                (string
+                  (quoted_content))
+                (identifier))
+              (identifier))))
+        (block
+          (let
+            (identifier)
+            (function_call
+              (field_access
+                (identifier)
+                (label))
+              (arguments
+                (argument
+                  (identifier)))))
+          (record
+            (constructor_name)
+            (arguments
+              (argument
+                (record
+                  (constructor_name)
+                  (arguments
+                    (argument
+                      (identifier))
+                    (argument
+                      (identifier)))))))))
+      (case_clause
+        (case_clause_patterns
+          (case_clause_pattern
+            (discard)))
+        (record
+          (constructor_name)
+          (arguments
+            (argument
+              (record
+                (constructor_name)))))))))