Another Bundle of Parser Fixes

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
     }
   }
@@ -321,6 +330,13 @@ extension Parser {
       } while keepGoing != nil && loopProgress.evaluate(currentToken)
     }
 
+    let whereClause: RawGenericWhereClauseSyntax?
+    if self.at(.whereKeyword) {
+      whereClause = self.parseGenericWhereClause()
+    } else {
+      whereClause = nil
+    }
+
     let rangle: RawTokenSyntax
     if self.currentToken.starts(with: ">") {
       rangle = self.consumeAnyToken(remapping: .rightAngle)
@@ -337,6 +353,7 @@ extension Parser {
     return RawGenericParameterClauseSyntax(
       leftAngleBracket: langle,
       genericParameterList: parameters,
+      genericWhereClause: whereClause,
       rightAngleBracket: rangle,
       arena: self.arena)
   }
@@ -1154,7 +1171,7 @@ extension Parser {
 
     // Parse the '!' or '?' for a failable initializer.
     let failable: RawTokenSyntax?
-    if let parsedFailable = self.consume(ifAny: [.exclamationMark, .postfixQuestionMark]) {
+    if let parsedFailable = self.consume(ifAny: [.exclamationMark, .postfixQuestionMark, .infixQuestionMark]) {
       failable = parsedFailable
     } else if let parsedFailable = self.consumeIfContextualPunctuator("!") {
       failable = parsedFailable
@@ -1373,7 +1390,7 @@ extension Parser {
     } else {
       unexpectedBeforeReturnType = nil
     }
-    let result = self.parseType()
+    let result = self.parseResultType()
     let returnClause = RawReturnClauseSyntax(
       unexpectedBeforeArrow,
       arrow: arrow,

Sources/SwiftParser/Expressions.swift

@@ -962,14 +962,21 @@ extension Parser {
   @_spi(RawSyntax)
   public mutating func parseIdentifierExpression() -> RawExprSyntax {
     let (name, args) = self.parseDeclNameRef(.compoundNames)
-    let identifier = RawIdentifierExprSyntax(
-      identifier: name, declNameArguments: args,
-      arena: self.arena)
-
     guard self.lookahead().canParseAsGenericArgumentList() else {
-      return RawExprSyntax(identifier)
+      if name.tokenText.hasPrefix("<#") && name.tokenText.hasSuffix("#>") && args == nil {
+        return RawExprSyntax(
+          RawEditorPlaceholderExprSyntax(
+            identifier: name,
+            arena: self.arena))
+      }
+      return RawExprSyntax(RawIdentifierExprSyntax(
+        identifier: name, declNameArguments: args,
+        arena: self.arena))
     }
 
+    let identifier = RawIdentifierExprSyntax(
+      identifier: name, declNameArguments: args,
+      arena: self.arena)
     let generics = self.parseGenericArguments()
     return RawExprSyntax(RawSpecializeExprSyntax(
       expression: RawExprSyntax(identifier), genericArgumentClause: generics,
@@ -1794,7 +1801,7 @@ extension Parser {
       // At this point, we know we have a closure signature. Parse the capture list
       // and parameters.
       var elements = [RawClosureCaptureItemSyntax]()
-      do {
+      if !self.at(.rightSquareBracket) {
         var keepGoing: RawTokenSyntax? = nil
         var loopProgress = LoopProgressCondition()
         repeat {

Sources/SwiftParser/Lexer.swift

@@ -904,7 +904,6 @@ extension Lexer.Cursor {
           _ = self.advanceToEndOfLine()
           continue
         case UInt8(ascii: "*"):
-          self = start
           _ = self.advanceToEndOfSlashStarComment()
           continue
         default:
@@ -1605,10 +1604,10 @@ extension Lexer.Cursor {
       if !self.isAtEndOfFile, self.peek() == UInt8(ascii: ".") && TokStart.peek() != UInt8(ascii: ".") {
         break
       }
-//      if (Identifier::isEditorPlaceholder(StringRef(CurPtr, BufferEnd-CurPtr)) &&
-//          rangeContainsPlaceholderEnd(CurPtr + 2, BufferEnd)) {
-//        break
-//      }
+      let text = SyntaxText(baseAddress: self.input.baseAddress, count: self.input.count)
+      if text.hasPrefix("<#") && text.containsPlaceholderEnd() {
+        break
+      }
 
 //      // If we are lexing a `/.../` regex literal, we don't consider `/` to be an
 //      // operator character.
@@ -2055,6 +2054,13 @@ extension Lexer.Cursor {
       case nil:
         return nil
       case UInt8(ascii: "/"):
+        // If we're at the end of the literal, peek ahead to see if the closing
+        // slash is actually the start of a comment.
+        if !Tmp.isAtEndOfFile &&
+            (Tmp.peek() == UInt8(ascii: "/") || Tmp.peek() == UInt8(ascii: "*")) {
+          return nil
+        }
+
         var EndLex = Tmp
         for _ in 0..<poundCount {
           guard EndLex.advance(matching: UInt8(ascii: "#")) != nil else {
@@ -2257,3 +2263,23 @@ extension Unicode.Scalar {
     return self.value >= 0x20 && self.value < 0x7F
   }
 }
+
+extension SyntaxText {
+  fileprivate func containsPlaceholderEnd() -> Bool {
+    guard self.count >= 2 else {
+      return false
+    }
+
+    for idx in 0..<(self.count - 1) {
+      let c = self[idx]
+      guard c != UInt8(ascii: "\n") else {
+        return false
+      }
+
+      if self[idx] == UInt8(ascii: "#"), self[idx+1] == UInt8(ascii: ">") {
+        return true
+      }
+    }
+    return false
+  }
+}

Sources/SwiftParser/Names.swift

@@ -132,7 +132,7 @@ extension Parser {
     let type: RawTypeSyntax?
     let dot: RawTokenSyntax?
     if self.lookahead().canParseBaseTypeForQualifiedDeclName() {
-      type = self.parseTypeIdentifier()
+      type = self.parseQualifiedTypeIdentifier()
       dot = self.consumePrefix(".", as: .period)
     } else {
       type = nil
@@ -151,6 +151,50 @@ extension Parser {
       arguments: args,
       arena: self.arena)
   }
+
+  @_spi(RawSyntax)
+  public mutating func parseQualifiedTypeIdentifier() -> RawTypeSyntax {
+    if self.at(.anyKeyword) {
+      return RawTypeSyntax(self.parseAnyType())
+    }
+
+    var result: RawTypeSyntax?
+    var keepGoing: RawTokenSyntax? = nil
+    var loopProgress = LoopProgressCondition()
+    repeat {
+      let (name, _) = self.parseDeclNameRef()
+      let generics: RawGenericArgumentClauseSyntax?
+      if self.atContextualPunctuator("<") {
+        generics = self.parseGenericArguments()
+      } else {
+        generics = nil
+      }
+      if let keepGoing = keepGoing {
+        result = RawTypeSyntax(RawMemberTypeIdentifierSyntax(
+          baseType: result!,
+          period: keepGoing,
+          name: name,
+          genericArgumentClause: generics,
+          arena: self.arena))
+      } else {
+        result = RawTypeSyntax(RawSimpleTypeIdentifierSyntax(
+          name: name, genericArgumentClause: generics, arena: self.arena))
+      }
+
+      // If qualified name base type cannot be parsed from the current
+      // point (i.e. the next type identifier is not followed by a '.'),
+      // then the next identifier is the final declaration name component.
+      var backtrack = self.lookahead()
+      backtrack.consumePrefix(".", as: .period)
+      guard backtrack.canParseBaseTypeForQualifiedDeclName() else {
+        break
+      }
+
+      keepGoing = self.consume(if: .period) ?? self.consume(if: .prefixPeriod)
+    } while keepGoing != nil && loopProgress.evaluate(currentToken)
+
+    return result!
+  }
 }
 
 extension Parser.Lookahead {

Sources/SwiftParser/Patterns.swift

@@ -117,7 +117,7 @@ extension Parser {
       return (pattern, nil)
     }
 
-    let result = self.parseType()
+    let result = self.parseResultType()
     let type = RawTypeAnnotationSyntax(
       colon: colon,
       type: result,

Sources/SwiftParser/Types.swift

@@ -185,7 +185,8 @@ extension Parser {
       ) {
         base = RawTypeSyntax(RawMetatypeTypeSyntax(
           baseType: base, period: period, typeOrProtocol: type, arena: self.arena))
-       }
+        continue
+      }
 
       if !self.currentToken.isAtStartOfLine {
         if self.currentToken.isOptionalToken {
@@ -860,6 +861,22 @@ extension Parser {
   }
 }
 
+extension Parser {
+  mutating func parseResultType() -> RawTypeSyntax {
+    if self.currentToken.starts(with: "<") {
+      let generics = self.parseGenericParameters()
+      let baseType = self.parseType()
+      return RawTypeSyntax(
+        RawNamedOpaqueReturnTypeSyntax(
+          genericParameters: generics,
+          baseType: baseType,
+          arena: self.arena))
+    } else {
+      return self.parseType()
+    }
+  }
+}
+
 extension Lexer.Lexeme {
   var isBinaryOperator: Bool {
     return self.tokenKind == .spacedBinaryOperator

Sources/SwiftSyntax/Documentation.docc/gyb_generated/SwiftSyntax.md

@@ -177,6 +177,7 @@ allows Swift tools to parse, inspect, generate, and transform Swift source code.
 - <doc:SwiftSyntax/TupleTypeSyntax>
 - <doc:SwiftSyntax/FunctionTypeSyntax>
 - <doc:SwiftSyntax/AttributedTypeSyntax>
+- <doc:SwiftSyntax/NamedOpaqueReturnTypeSyntax>
 
 ### Patterns