[SwiftParser] Account for a newline between nonisolated and (

Author: xedin

Sources/SwiftParser/Types.swift

@@ -689,7 +689,6 @@ extension Parser.Lookahead {
 
   mutating func skipTypeAttributeList() {
     var specifierProgress = LoopProgressCondition()
-    // TODO: Can we model isolated/_const so that they're specified in both canParse* and parse*?
     while canHaveParameterSpecifier,
       self.at(anyIn: SimpleTypeSpecifierSyntax.SpecifierOptions.self) != nil
         || self.at(.keyword(.nonisolated), .keyword(.dependsOn)),
@@ -701,7 +700,7 @@ extension Parser.Lookahead {
 
         // The argument is missing but it still could be a valid modifier,
         // i.e. `nonisolated` in an inheritance clause.
-        guard self.at(.leftParen) else {
+        guard self.at(.leftParen), !self.currentToken.isAtStartOfLine else {
           continue
         }
 
@@ -1178,6 +1177,11 @@ extension Parser {
           break SPECIFIER_PARSING
         }
       } else if self.at(.keyword(.nonisolated)) {
+        // If '(' is located on the new line 'nonisolated' cannot be parsed
+        // as a specifier.
+        if self.peek(isAt: .leftParen) && self.peek().isAtStartOfLine {
+          break SPECIFIER_PARSING
+        }
         specifiers.append(parseNonisolatedTypeSpecifier())
       } else {
         break SPECIFIER_PARSING

Tests/SwiftParserTest/TypeTests.swift

@@ -565,6 +565,25 @@ final class TypeTests: ParserTestCase {
     assertParse("struct S : nonisolated P {}")
     assertParse("let _ = [nonisolated()]")
 
+    assertParse("""
+      let x: nonisolated
+      (hello)
+      """
+    )
+
+    assertParse("""
+      struct S: nonisolated
+                  P {
+      }
+      """
+    )
+
+    assertParse("""
+      let x: nonisolated
+          (Int) async -> Void  = {}
+      """
+    )
+
     assertParse(
       "Foo<Int, nonisolated1️⃣ @Sendable (Int, inout (any Actor)?) async throws -> Void>()",
       diagnostics: [