Merge pull request swiftlang#637 from omochi/fix-nested-interpolation-crash

Fix crash on nested interpolation

Author: CodaFi

Sources/SwiftParser/Lexer.swift

@@ -1029,7 +1029,7 @@ extension Lexer.Cursor {
       }
       if !self.isAtEndOfFile, self.peek() == UInt8(ascii: "\\") &&
            TmpPtr.delimiterMatches(customDelimiterLength) &&
-            TmpPtr.advance() == UInt8(ascii: "(") {
+            TmpPtr.peek() == UInt8(ascii: "(") {
         // Consume tokens until we hit the corresponding ')'.
         self = Self.skipToEndOfInterpolatedExpression(TmpPtr, IsMultilineString)
         if self.advance(if: { $0 == Unicode.Scalar(")") }) {

Tests/SwiftParserTest/Expressions.swift

@@ -194,6 +194,24 @@ final class ExpressionTests: XCTestCase {
       return "Fixit: \(range.debugDescription) Text: \"\(text)\""
       """#
     }
+
+    try AssertParse({ $0.parseExpression() }) {
+      #"""
+      "text \(array.map({ "\($0)" }).joined(separator: ",")) text"
+      """#
+    }
+
+    try AssertParse({ $0.parseExpression() }) {
+      #"""
+      """
+      \(gen(xx) { (x) in
+          return """
+          case
+      """
+      })
+      """
+      """#
+    }
   }
 
   func testStringLiterals() throws {