[ASTGen] Simplify diagnostics framework

This simplifies both the diagnostic declarations and usages.

To create a new diangnostic message, create a static method:

  extension ASTGenDiagnostic {
    static func invalidToken(_ token: TokenSyntax) -> Self {
      return Self(
        node: token,
        message: "invalid token: '\(token.trimmed)'"
      )
    }
  }

To use it In ASTGenVisitor:

  self.diagnose(.invalidToken(token))

Author: rintaro

lib/ASTGen/Sources/ASTGen/ASTGen.swift

@@ -69,7 +69,7 @@ class Boxed<Value> {
 }
 
 struct ASTGenVisitor {
-  fileprivate let diagnosticEngine: BridgedDiagnosticEngine
+  let diagnosticEngine: BridgedDiagnosticEngine
 
   let base: UnsafeBufferPointer<UInt8>
 
@@ -273,24 +273,6 @@ extension ASTGenVisitor {
   }
 }
 
-extension ASTGenVisitor {
-  /// Emits the given diagnostic via the C++ diagnostic engine.
-  @inline(__always)
-  func diagnose(_ diagnostic: Diagnostic) {
-    emitDiagnostic(
-      diagnosticEngine: self.diagnosticEngine,
-      sourceFileBuffer: self.base,
-      diagnostic: diagnostic,
-      diagnosticSeverity: diagnostic.diagMessage.severity
-    )
-  }
-
-  /// Emits the given diagnostics via the C++ diagnostic engine.
-  func diagnoseAll(_ diagnostics: [Diagnostic]) {
-    diagnostics.forEach(diagnose)
-  }
-}
-
 // Forwarding overloads that take optional syntax nodes. These are defined on demand to achieve a consistent
 // 'self.generate(foo: FooSyntax)' recursion pattern between optional and non-optional inputs.
 extension ASTGenVisitor {

lib/ASTGen/Sources/ASTGen/Decls.swift

@@ -340,7 +340,7 @@ extension ASTGenVisitor {
     case .`init`:
       return .`init`
     default:
-      self.diagnose(Diagnostic(node: specifier, message: UnknownAccessorSpecifierError(specifier)))
+      self.diagnose(.unknownAccessorSpecifier(specifier))
       return nil
     }
   }
@@ -448,7 +448,7 @@ extension ASTGenVisitor {
         let storage = primaryVar.asAbstractStorageDecl
         storage.setAccessors(generate(accessorBlock: accessors, for: storage))
       } else {
-        self.diagnose(Diagnostic(node: binding.pattern, message: NonTrivialPatternForAccessorError()))
+        self.diagnose(.nonTrivialPatternForAccessor(binding.pattern))
       }
     }
     return BridgedPatternBindingEntry(
@@ -667,9 +667,7 @@ extension ASTGenVisitor {
       fixity = value
     } else {
       fixity = .infix
-      self.diagnose(
-        Diagnostic(node: node.fixitySpecifier, message: UnexpectedTokenKindError(token: node.fixitySpecifier))
-      )
+      self.diagnose(.unexpectedTokenKind(token: node.fixitySpecifier))
     }
 
     return .createParsed(
@@ -712,9 +710,7 @@ extension ASTGenVisitor {
     }
 
     func diagnoseDuplicateSyntax(_ duplicate: some SyntaxProtocol, original: some SyntaxProtocol) {
-      self.diagnose(
-        Diagnostic(node: duplicate, message: DuplicateSyntaxError(duplicate: duplicate, original: original))
-      )
+      self.diagnose(.duplicateSyntax(duplicate: duplicate, original: original))
     }
 
     let body = node.groupAttributes.reduce(into: PrecedenceGroupBody()) { body, element in
@@ -735,7 +731,7 @@ extension ASTGenVisitor {
             body.lowerThanRelation = relation
           }
         default:
-          return self.diagnose(Diagnostic(node: keyword, message: UnexpectedTokenKindError(token: keyword)))
+          return self.diagnose(.unexpectedTokenKind(token: keyword))
         }
       case .precedenceGroupAssignment(let assignment):
         if let current = body.assignment {
@@ -757,7 +753,7 @@ extension ASTGenVisitor {
       if let value = BridgedAssociativity(from: token.keywordKind) {
         associativityValue = value
       } else {
-        self.diagnose(Diagnostic(node: token, message: UnexpectedTokenKindError(token: token)))
+        self.diagnose(.unexpectedTokenKind(token: token))
         associativityValue = .none
       }
     } else {
@@ -769,7 +765,7 @@ extension ASTGenVisitor {
       if token.keywordKind == .true {
         assignmentValue = true
       } else {
-        self.diagnose(Diagnostic(node: token, message: UnexpectedTokenKindError(token: token)))
+        self.diagnose(.unexpectedTokenKind(token: token))
         assignmentValue = false
       }
     } else {
@@ -824,7 +820,7 @@ extension ASTGenVisitor {
       if let value = BridgedImportKind(from: specifier.keywordKind) {
         importKind = value
       } else {
-        self.diagnose(Diagnostic(node: specifier, message: UnexpectedTokenKindError(token: specifier)))
+        self.diagnose(.unexpectedTokenKind(token: specifier))
         importKind = .module
       }
     } else {

lib/ASTGen/Sources/ASTGen/Diagnostics.swift

@@ -13,65 +13,90 @@
 import SwiftDiagnostics
 import SwiftSyntax
 
-protocol ASTGenError: DiagnosticMessage {}
+extension ASTGenVisitor {
+  /// Emits the given ASTGen diagnostic via the C++ diagnostic engine.
+  func diagnose(_ message: ASTGenDiagnostic, highlights: [Syntax]? = nil, notes: [Note] = [], fixIts: [FixIt] = []) {
+    self.diagnose(Diagnostic(
+      node: message.node,
+      message: message,
+      highlights: highlights,
+      notes: notes,
+      fixIts: fixIts
+    ))
+  }
 
-extension ASTGenError {
-  var diagnosticID: MessageID {
-    MessageID(domain: "ASTGen", id: "\(Self.self)")
+  /// Emits the given diagnostic via the C++ diagnostic engine.
+  func diagnose(_ diagnostic: Diagnostic) {
+    emitDiagnostic(
+      diagnosticEngine: self.diagnosticEngine,
+      sourceFileBuffer: self.base,
+      diagnostic: diagnostic,
+      diagnosticSeverity: diagnostic.diagMessage.severity
+    )
   }
 
-  var severity: DiagnosticSeverity { .error }
+  /// Emits the given diagnostics via the C++ diagnostic engine.
+  func diagnoseAll(_ diagnostics: [Diagnostic]) {
+    diagnostics.forEach(diagnose)
+  }
 }
 
-/// An error emitted when a token is of an unexpected kind.
-struct UnexpectedTokenKindError: ASTGenError {
-  let token: TokenSyntax
-  private let parent: Syntax
+struct ASTGenDiagnostic: DiagnosticMessage {
+  var node: Syntax
+  var message: String
+  var severity: DiagnosticSeverity
+  var messageID: String
 
-  init(token: TokenSyntax) {
-    guard let parent = token.parent else {
-      preconditionFailure("Expected a child (not a root) token")
-    }
+  var diagnosticID: MessageID {
+    MessageID(domain: "ASTGen", id: messageID)
+  }
 
-    self.token = token
-    self.parent = parent
+  init(node: some SyntaxProtocol, message: String, severity: DiagnosticSeverity = .error, messageID: String) {
+    self.node = Syntax(node)
+    self.message = message
+    self.severity = severity
+    self.messageID = messageID
   }
 
-  var message: String {
-    return """
-      unexpected token kind for token:
-        \(self.token.debugDescription)
-      in parent:
-        \(self.parent.debugDescription(indentString: "  "))
-      """
+  fileprivate init(node: some SyntaxProtocol, message: String, severity: DiagnosticSeverity = .error, function: String = #function) {
+    // Extract messageID from the function name.
+    let messageID = String(function.prefix(while: { $0 != "(" }))
+    self.init(node: node, message: message, severity: severity, messageID: messageID)
   }
 }
 
-/// An error emitted when an optional child token is unexpectedly nil.
-struct MissingChildTokenError: ASTGenError {
-  let parent: Syntax
-  let kindOfTokenMissing: TokenKind
+extension ASTGenDiagnostic {
+  /// An error emitted when a token is of an unexpected kind.
+  static func unexpectedTokenKind(token: TokenSyntax) -> Self {
+    guard let parent = token.parent else {
+      preconditionFailure("Expected a child (not a root) token")
+    }
 
-  init(parent: some SyntaxProtocol, kindOfTokenMissing: TokenKind) {
-    self.parent = Syntax(parent)
-    self.kindOfTokenMissing = kindOfTokenMissing
+    return Self(
+      node: token,
+      message: """
+      unexpected token kind for token:
+        \(token.debugDescription)
+      in parent:
+        \(parent.debugDescription(indentString: "  "))
+      """
+    )
   }
 
-  var message: String {
-    """
-    missing child token of kind '\(self.kindOfTokenMissing)' in:
-      \(parent.debugDescription(indentString: "  "))
-    """
+  /// An error emitted when an optional child token is unexpectedly nil.
+  static func missingChildToken(parent: some SyntaxProtocol, kindOfTokenMissing: TokenKind) -> Self {
+    Self(
+      node: parent,
+      message: """
+      missing child token of kind '\(kindOfTokenMissing)' in:
+        \(parent.debugDescription(indentString: "  "))
+      """
+    )
   }
-}
 
-/// An error emitted when a syntax collection entry is encountered that is considered a duplicate of a previous entry
-/// per the language grammar.
-struct DuplicateSyntaxError: ASTGenError {
-  let duplicate: Syntax
-  let original: Syntax
-
-  init(duplicate: some SyntaxProtocol, original: some SyntaxProtocol) {
+  /// An error emitted when a syntax collection entry is encountered that is
+  /// considered a duplicate of a previous entry per the language grammar.
+  static func duplicateSyntax(duplicate: some SyntaxProtocol, original: some SyntaxProtocol) -> Self {
     precondition(duplicate.kind == original.kind, "Expected duplicate and original to be of same kind")
 
     guard let duplicateParent = duplicate.parent, let originalParent = original.parent,
@@ -80,42 +105,28 @@ struct DuplicateSyntaxError: ASTGenError {
       preconditionFailure("Expected a shared syntax collection parent")
     }
 
-    self.duplicate = Syntax(duplicate)
-    self.original = Syntax(original)
-  }
-
-  var message: String {
-    """
-    unexpected duplicate syntax in list:
-      \(duplicate.debugDescription(indentString: "  "))
-    previous syntax:
-      \(original.debugDescription(indentString: "  "))
-    """
-  }
-}
-
-struct NonTrivialPatternForAccessorError: ASTGenError {
-  var message: String {
-    "getter/setter can only be defined for a single variable"
-  }
-}
-
-struct UnknownAccessorSpecifierError: ASTGenError {
-  var specifier: TokenSyntax
-  init(_ specifier: TokenSyntax) {
-    self.specifier = specifier
+    return Self(
+      node: duplicate,
+      message: """
+      unexpected duplicate syntax in list:
+        \(duplicate.debugDescription(indentString: "  "))
+      previous syntax:
+        \(original.debugDescription(indentString: "  "))
+      """
+    )
   }
 
-  var message: String {
-    "unknown accessor specifier '\(specifier.text)'"
+  static func nonTrivialPatternForAccessor(_ pattern: some SyntaxProtocol) -> Self {
+    Self(
+      node: pattern,
+      message: "getter/setter can only be defined for a single variable"
+    )
   }
-}
 
-struct RegexParserError: ASTGenError {
-  var message: String
-  init(_ message: String) {
-    self.message = message
+  static func unknownAccessorSpecifier(_ specifier: TokenSyntax) -> Self {
+    Self(
+      node: specifier,
+      message: "unknown accessor specifier '\(specifier.text)'"
+    )
   }
-
-  var severity: DiagnosticSeverity { .error }
 }

lib/ASTGen/Sources/ASTGen/Exprs.swift

@@ -406,14 +406,10 @@ extension ASTGenVisitor {
   func generate(functionCallExpr node: FunctionCallExprSyntax, postfixIfConfigBaseExpr: BridgedExpr? = nil) -> BridgedCallExpr {
     if !node.arguments.isEmpty || node.trailingClosure == nil {
       if node.leftParen == nil {
-        self.diagnose(
-          Diagnostic(node: node, message: MissingChildTokenError(parent: node, kindOfTokenMissing: .leftParen))
-        )
+        self.diagnose(.missingChildToken(parent: node, kindOfTokenMissing: .leftParen))
       }
       if node.rightParen == nil {
-        self.diagnose(
-          Diagnostic(node: node, message: MissingChildTokenError(parent: node, kindOfTokenMissing: .rightParen))
-        )
+        self.diagnose(.missingChildToken(parent: node, kindOfTokenMissing: .rightParen))
       }
     }
 

lib/ASTGen/Sources/ASTGen/Types.swift

@@ -367,7 +367,7 @@ extension ASTGenVisitor {
             specifierLoc: self.generateSourceLoc(specifier)
           ).asTypeRepr
       } else {
-        self.diagnose(Diagnostic(node: specifier, message: UnexpectedTokenKindError(token: specifier)))
+        self.diagnose(.unexpectedTokenKind(token: specifier))
       }
     }