Patch a Regression in Declaration Lookahead

Author: CodaFi

Sources/SwiftParser/Declarations.swift

@@ -30,14 +30,16 @@ extension TokenConsumer {
       _ = subparser.consumeAttributeList()
     }
 
-    var modifierProgress = LoopProgressCondition()
-    while let (modifierKind, handle) = subparser.at(anyIn: DeclarationModifier.self),
-            modifierKind != .classKeyword,
-            modifierProgress.evaluate(subparser.currentToken) {
-      subparser.eat(handle)
-      if subparser.at(.leftParen) {
-        subparser.consumeAnyToken()
-        subparser.consume(to: .rightParen)
+    if subparser.currentToken.isKeyword {
+      var modifierProgress = LoopProgressCondition()
+      while let (modifierKind, handle) = subparser.at(anyIn: DeclarationModifier.self),
+              modifierKind != .classKeyword,
+              modifierProgress.evaluate(subparser.currentToken) {
+        subparser.eat(handle)
+        if subparser.at(.leftParen) {
+          subparser.consumeAnyToken()
+          subparser.consume(to: .rightParen)
+        }
       }
     }
 
@@ -75,10 +77,17 @@ extension TokenConsumer {
         lookahead.consumeAnyToken()
       } while lookahead.atStartOfDeclaration()
       return lookahead.at(.identifier)
-    case .caseKeyword, nil:
+    case .caseKeyword:
       // When 'case' appears inside a function, it's probably a switch
       // case, not an enum case declaration.
       return false
+    case nil:
+      if subparser.at(anyIn: ContextualDeclKeyword.self)?.0 != nil {
+        subparser.consumeAnyToken()
+        return subparser.atStartOfDeclaration(
+          isAtTopLevel: isAtTopLevel, allowRecovery: allowRecovery)
+      }
+      return false
     default: return true
     }
   }

Tests/SwiftParserTest/Declarations.swift

@@ -148,6 +148,13 @@ final class DeclarationTests: XCTestCase {
   }
 
   func testVariableDeclarations() {
+    AssertParse(
+      """
+      z
+
+      var x: Double = z
+      """)
+    
     AssertParse(
       """
       async let a = fetch("1.jpg")

Tests/SwiftParserTest/Expressions.swift

@@ -48,6 +48,11 @@ final class ExpressionTests: XCTestCase {
 
   func testSequenceExpressions() {
     AssertParse("await a()")
+    AssertParse(
+      """
+      async let child = testNestedTaskPriority(basePri: basePri, curPri: curPri)
+      await child
+      """)
   }
 
   func testNestedTypeSpecialization() {
@@ -508,4 +513,13 @@ final class ExpressionTests: XCTestCase {
     AssertParse("if <#test#> {}")
     AssertParse("if <#b1#>, <#b2#> {}")
   }
+
+  func testKeywordApplyExpression() {
+    AssertParse(
+      """
+      optional(x: .some(23))
+      optional(x: .none)
+      var pair : (Int, Double) = makePair(a: 1, b: 2.5)
+      """)
+  }
 }