Parse subscript expression with no arguments (e.g., array[]).

Author: DougGregor

Sources/SwiftParser/Expressions.swift

@@ -594,7 +594,12 @@ extension Parser {
       // Check for a [expr] suffix.
       // Note that this cannot be the start of a new line.
       if let lsquare = self.consume(if: .leftSquareBracket, where: { !$0.isAtStartOfLine }) {
-        let args = self.parseArgumentListElements(inLetOrVar: inLetOrVar)
+        let args: [RawTupleExprElementSyntax]
+        if self.at(.rightSquareBracket) {
+          args = []
+        } else {
+          args = self.parseArgumentListElements(inLetOrVar: inLetOrVar)
+        }
         let (unexpectedBeforeRSquare, rsquare) = self.expect(.rightSquareBracket)
 
         // If we can parse trailing closures, do so.

Tests/SwiftParserTest/Expressions.swift

@@ -431,7 +431,13 @@ final class ExpressionTests: XCTestCase {
     )
   }
 
-  func testRangeSubscript() {
+  func testSubscript() {
+    AssertParse(
+      """
+      array[]
+      """
+    )
+
     AssertParse(
       """
       text[...]