Handle unexpected token before in keyword

Author: kimdv

Sources/SwiftParser/TokenPrecedence.swift

@@ -203,17 +203,17 @@ enum TokenPrecedence: Comparable {
       // Consider 'any' a prefix operator to a type and a type is expression-like.
       .Any,
       // 'where' can only occur in the signature of declarations. Consider the signature expression-like.
-      .where,
-      // 'in' occurs in closure input/output definitions and for loops. Consider both constructs expression-like.
-      .in:
+      .where:
       self = .exprKeyword
 
     case  // Control-flow constructs
     .defer, .do, .for, .guard, .if, .repeat, .switch, .while,
       // Secondary parts of control-flow constructs
       .case, .catch, .default, .else,
       // Return-like statements
-      .break, .continue, .fallthrough, .return, .throw, .then, .yield:
+      .break, .continue, .fallthrough, .return, .throw, .then, .yield,
+      // 'in' occurs in closure input/output definitions and for loops. Consider both constructs expression-like.
+      .in:
       self = .stmtKeyword
 
     // MARK: Decl keywords

Tests/SwiftParserTest/StatementTests.swift

@@ -921,4 +921,13 @@ final class StatementTests: ParserTestCase {
       """
     )
   }
+
+  func testForStatementWithUnexpectedTokenBeforeInKeyword() {
+    assertParse(
+      "for var elem1️⃣? in arr { }",
+      diagnostics: [
+        DiagnosticSpec(message: "unexpected code '?' in 'for' statement")
+      ]
+    )
+  }
 }