Improve recovery of unknown pound literals

Sources/SwiftParser/Diagnostics/ParseDiagnosticsGenerator.swift

@@ -441,6 +441,18 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: IdentifierExprSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+    if node.identifier.presence == .missing,
+       let unexpected = node.unexpectedBeforeIdentifier,
+       unexpected.first?.as(TokenSyntax.self)?.tokenKind == .pound {
+      addDiagnostic(unexpected, UnknownDirectiveError(unexpected: unexpected), handledNodes: [unexpected.id, node.identifier.id])
+    }
+    return .visitChildren
+  }
+
   public override func visit(_ node: PrecedenceGroupAssignmentSyntax) -> SyntaxVisitorContinueKind {
     if shouldSkip(node) {
       return .skipChildren

Sources/SwiftParser/Diagnostics/ParserDiagnosticMessages.swift

@@ -183,6 +183,14 @@ public struct UnexpectedNodesError: ParserError {
   }
 }
 
+public struct UnknownDirectiveError: ParserError {
+  public let unexpected: UnexpectedNodesSyntax
+
+  public var message: String {
+    return "use of unknown directive \(nodesDescription([unexpected], format: false))"
+  }
+}
+
 // MARK: - Fix-Its (please sort alphabetically)
 
 public enum StaticParserFixIt: String, FixItMessage {

Sources/SwiftParser/Expressions.swift

@@ -1112,6 +1112,8 @@ extension Parser {
         wildcard: wild,
         arena: self.arena
       ))
+    case (.pound, let handle)?:
+      return RawExprSyntax(self.parseUnknownPoundLiteral(poundHandle: handle))
     case (.poundSelectorKeyword, _)?:
       return RawExprSyntax(self.parseObjectiveCSelectorLiteral())
     case (.poundKeyPathKeyword, _)?:
@@ -1209,6 +1211,32 @@ extension Parser {
   }
 }
 
+extension Parser {
+  /// Parse an unknown pound literal, that starts with a `#` at `poundHandle`
+  /// into a `RawIdentifierExprSyntax` that is missing the identifier and
+  /// instead contains all the tokens of the pound literal as unexpected tokens.
+  mutating func parseUnknownPoundLiteral(poundHandle: TokenConsumptionHandle) -> RawIdentifierExprSyntax {
+    var unexpected: [RawSyntax] = []
+    unexpected.append(RawSyntax(self.eat(poundHandle)))
+    if let name = self.consume(if: .identifier) {
+      unexpected.append(RawSyntax(name))
+    }
+    // If there is a parenthesis, consume all tokens up to the closing parenthesis.
+    if let leftParen = self.consume(if: .leftParen) {
+      unexpected.append(RawSyntax(leftParen))
+      let (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
+      unexpected += unexpectedBeforeRightParen?.elements ?? []
+      unexpected.append(RawSyntax(rightParen))
+    }
+    return RawIdentifierExprSyntax(
+      RawUnexpectedNodesSyntax(elements: unexpected, arena: self.arena),
+      identifier: missingToken(.identifier, text: nil),
+      declNameArguments: nil,
+      arena: self.arena
+    )
+  }
+}
+
 extension Parser {
   /// Parse a string literal expression.
   ///

Sources/SwiftParser/RawTokenKindSubset.swift

@@ -726,6 +726,7 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
   case leftSquareBracket
   case nilKeyword
   case period
+  case pound // For recovery of unknown directives
   case poundColorLiteralKeyword
   case poundColumnKeyword
   case poundDsohandleKeyword
@@ -765,6 +766,7 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
     case .leftSquareBracket: self = .leftSquareBracket
     case .nilKeyword: self = .nilKeyword
     case .period: self = .period
+    case .pound: self = .pound
     case .poundColorLiteralKeyword: self = .poundColorLiteralKeyword
     case .poundColumnKeyword: self = .poundColumnKeyword
     case .poundDsohandleKeyword: self = .poundDsohandleKeyword
@@ -807,6 +809,7 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
     case .leftSquareBracket: return .leftSquareBracket
     case .nilKeyword: return .nilKeyword
     case .period: return .period
+    case .pound: return .pound
     case .poundColorLiteralKeyword: return .poundColorLiteralKeyword
     case .poundColumnKeyword: return .poundColumnKeyword
     case .poundDsohandleKeyword: return .poundDsohandleKeyword

Tests/SwiftParserTest/translated/DollarIdentifierTests.swift

@@ -236,7 +236,7 @@ final class DollarIdentifierTests: XCTestCase {
         // TODO: Old parser expected error on line 32: cannot declare entity named '$Protocol'; the '$' prefix is reserved
         // TODO: Old parser expected error on line 33: cannot declare entity named '$Precedence'; the '$' prefix is reserved
         // TODO: Old parser expected error on line 37: use of unknown directive '#$UnknownDirective'
-        DiagnosticSpec(message: "extraneous code '#$UnknownDirective()' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#$UnknownDirective()'"),
       ]
     )
   }

Tests/SwiftParserTest/translated/ObjectLiteralsTests.swift

@@ -3,33 +3,50 @@
 import XCTest
 
 final class ObjectLiteralsTests: XCTestCase {
-  func testObjectLiterals1() {
+  func testObjectLiterals1a() {
     AssertParse(
       """
-      let _ = [1️⃣#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)#] 
-      let _ = [2️⃣#Image(imageLiteral: localResourceNameAsString)#] 
-      let _ = [3️⃣#FileReference(fileReferenceLiteral: localResourceNameAsString)#]
+      let _ = [1️⃣#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)2️⃣#]
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '[#Color(...)#]' has been renamed to '#colorLiteral(...), Fix-It replacements: 9 - 10 = '', 11 - 16 = 'colorLiteral', 17 - 32 = 'red', 78 - 80 = ''
-        DiagnosticSpec(locationMarker: "1️⃣", message: "unexpected code '#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)#' in array"),
-        // TODO: Old parser expected error on line 2: '[#Image(...)#]' has been renamed to '#imageLiteral(...)', Fix-It replacements: 9 - 10 = '', 11 - 16 = 'imageLiteral', 17 - 29 = 'resourceName', 57 - 59 = ''
-        DiagnosticSpec(locationMarker: "2️⃣", message: "unexpected code '#Image(imageLiteral: localResourceNameAsString)#' in array"),
-        // TODO: Old parser expected error on line 3: '[#FileReference(...)#]' has been renamed to '#fileLiteral(...)', Fix-It replacements: 9 - 10 = '', 11 - 24 = 'fileLiteral', 25 - 45 = 'resourceName', 73 - 75 = ''
-        DiagnosticSpec(locationMarker: "3️⃣", message: "unexpected code '#FileReference(fileReferenceLiteral: localResourceNameAsString)#' in array"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
       ]
     )
   }
 
+  func testObjectLiterals1b() {
+    AssertParse(
+      """
+      let _ = [1️⃣#Image(imageLiteral: localResourceNameAsString)2️⃣#]
+      """,
+      diagnostics: [
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#Image(imageLiteral: localResourceNameAsString)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
+      ]
+    )
+  }
+
+  func testObjectLiterals1c() {
+    AssertParse(
+      """
+      let _ = [1️⃣#FileReference(fileReferenceLiteral: localResourceNameAsString)2️⃣#]
+      """,
+      diagnostics: [
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#FileReference(fileReferenceLiteral: localResourceNameAsString)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
+      ]
+    )
+  }
+
+
   func testObjectLiterals2a() {
     AssertParse(
       """
       let _ = 1️⃣#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '#Color(...)' has been renamed to '#colorLiteral(...), Fix-It replacements: 10 - 15 = 'colorLiteral', 16 - 31 = 'red'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#Color(colorLiteralRed: red, green: green, blue: blue, alpha: alpha)'"),
       ]
     )
   }
@@ -40,9 +57,7 @@ final class ObjectLiteralsTests: XCTestCase {
       let _ = 1️⃣#Image(imageLiteral: localResourceNameAsString)
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '#Image(...)' has been renamed to '#imageLiteral(...)', Fix-It replacements: 10 - 15 = 'imageLiteral', 16 - 28 = 'resourceName'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#Image(imageLiteral: localResourceNameAsString)' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#Image(imageLiteral: localResourceNameAsString)'"),
       ]
     )
   }
@@ -54,9 +69,7 @@ final class ObjectLiteralsTests: XCTestCase {
       let _ = 1️⃣#FileReference(fileReferenceLiteral: localResourceNameAsString)
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '#FileReference(...)' has been renamed to '#fileLiteral(...)', Fix-It replacements: 10 - 23 = 'fileLiteral', 24 - 44 = 'resourceName'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#FileReference(fileReferenceLiteral: localResourceNameAsString)' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#FileReference(fileReferenceLiteral: localResourceNameAsString)'"),
       ]
     )
   }
@@ -68,9 +81,7 @@ final class ObjectLiteralsTests: XCTestCase {
       let _ = 1️⃣#notAPound
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: use of unknown directive '#notAPound'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#notAPound' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#notAPound'"),
       ]
     )
   }
@@ -81,72 +92,67 @@ final class ObjectLiteralsTests: XCTestCase {
       let _ = 1️⃣#notAPound(1, 2)
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: use of unknown directive '#notAPound'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#notAPound(1, 2)' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#notAPound(1, 2)'"),
       ]
     )
   }
 
   func testObjectLiterals3c() {
     AssertParse(
       """
-      let _ = 1️⃣#Color //  {{none}}
+      let _ = 1️⃣#Color
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: expected argument list in object literal
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#Color' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#Color'"),
       ]
     )
   }
 
   func testObjectLiterals4() {
     AssertParse(
       """
-      let _ = [1️⃣##] //  {{none}}
+      let _ = [1️⃣#2️⃣#]
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: expected expression in container literal
-        DiagnosticSpec(message: "unexpected code '##' in array"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
       ]
     )
   }
 
   func testObjectLiterals5() {
     AssertParse(
       """
-      let _ = [1️⃣#Color(_: 1, green: 1, 2)
+      let _ = [1️⃣#Color(_: 1, green: 1, 2)2️⃣
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '[#Color(...)#]' has been renamed to '#colorLiteral(...)', Fix-It replacements: 9 - 10 = '', 11 - 16 = 'colorLiteral', 17 - 18 = 'red'
-        DiagnosticSpec(message: "expected ']' to end array"),
-        DiagnosticSpec(message: "extraneous code '#Color(_: 1, green: 1, 2)' at top level"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#Color(_: 1, green: 1, 2)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "expected ']' to end array"),
       ]
     )
   }
 
   func testObjectLiterals6() {
     AssertParse(
       """
-      let _ = [1️⃣#Color(red: 1, green: 1, blue: 1)#
+      let _ = [1️⃣#Color(red: 1, green: 1, blue: 1)2️⃣#3️⃣
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '[#Color(...)#]' has been renamed to '#colorLiteral(...)', Fix-It replacements: 9 - 10 = '', 11 - 16 = 'colorLiteral', 17 - 20 = 'red', 43 - 44 = ''
-        DiagnosticSpec(message: "expected ']' to end array"),
-        DiagnosticSpec(message: "extraneous code '#Color(red: 1, green: 1, blue: 1)#' at top level"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#Color(red: 1, green: 1, blue: 1)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "3️⃣", message: "expected ']' to end array"),
       ]
     )
   }
 
   func testObjectLiterals7() {
     AssertParse(
       """
-      let _ = [1️⃣#Color(withRed: 1, green: 1, whatever: 2)#]
+      let _ = [1️⃣#Color(withRed: 1, green: 1, whatever: 2)2️⃣#]
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '[#Color(...)#]' has been renamed to '#colorLiteral(...)', Fix-It replacements: 9 - 10 = '', 11 - 16 = 'colorLiteral', 17 - 24 = 'red', 51 - 53 = ''
-        DiagnosticSpec(message: "unexpected code '#Color(withRed: 1, green: 1, whatever: 2)#' in array"),
+        DiagnosticSpec(message: "use of unknown directive '#Color(withRed: 1, green: 1, whatever: 2)'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'")
       ]
     )
   }
@@ -157,9 +163,7 @@ final class ObjectLiteralsTests: XCTestCase {
       let _ = 1️⃣#Color(_: 1, green: 1)
       """,
       diagnostics: [
-        // TODO: Old parser expected error on line 1: '#Color(...)' has been renamed to '#colorLiteral(...)', Fix-It replacements: 10 - 15 = 'colorLiteral', 16 - 17 = 'red'
-        DiagnosticSpec(message: "expected expression in variable"),
-        DiagnosticSpec(message: "extraneous code '#Color(_: 1, green: 1)' at top level"),
+        DiagnosticSpec(message: "use of unknown directive '#Color(_: 1, green: 1)'"),
       ]
     )
   }

Tests/SwiftParserTest/translated/RawStringErrorsTests.swift

@@ -34,13 +34,16 @@ final class RawStringErrorsTests: XCTestCase {
   func testRawStringErrors3() {
     AssertParse(
       #####"""
-      let _ = ###"""invalid"###1️⃣###
+      let _ = ###"""invalid"###1️⃣#2️⃣#3️⃣#
       """#####,
       diagnostics: [
         // TODO: Old parser expected error on line 1: too many '#' characters in closing delimiter, Fix-It replacements: 26 - 29 = ''
         // TODO: Old parser expected error on line 1: consecutive statements on a line must be separated by ';'
         // TODO: Old parser expected error on line 1: expected expression
-        DiagnosticSpec(message: "extraneous code '###' at top level"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "consecutive statements on a line must be separated by ';'"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "3️⃣", message: "use of unknown directive '#'"),
       ]
     )
   }
@@ -60,13 +63,16 @@ final class RawStringErrorsTests: XCTestCase {
   func testRawStringErrors5() {
     AssertParse(
       #####"""
-      let _ = ###"invalid"###1️⃣###
+      let _ = ###"invalid"###1️⃣#2️⃣#3️⃣#
       """#####,
       diagnostics: [
         // TODO: Old parser expected error on line 1: too many '#' characters in closing delimiter, Fix-It replacements: 24 - 27 = ''
         // TODO: Old parser expected error on line 1: consecutive statements on a line must be separated by ';'
         // TODO: Old parser expected error on line 1: expected expression
-        DiagnosticSpec(message: "extraneous code '###' at top level"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "consecutive statements on a line must be separated by ';'"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "use of unknown directive '#'"),
+        DiagnosticSpec(locationMarker: "3️⃣", message: "use of unknown directive '#'"),
       ]
     )
   }