Add diagnostics for init declarations

Author: StevenWong12

Sources/SwiftParser/Declarations.swift

@@ -1061,6 +1061,14 @@ extension Parser {
     // Parse the signature.
     let signature = self.parseFunctionSignature()
 
+    // mark the unexpected result type of initializer
+    // and replace the ‘output‘ of signature with nil
+    var unexpectedResultType: RawUnexpectedNodesSyntax?
+    if let output = signature.output {
+      signature.raw = signature.layoutView.replacingChild(at: 5, with: nil, arena: self.arena)
+      unexpectedResultType = RawUnexpectedNodesSyntax([output.raw], arena: self.arena)
+    }
+
     let whereClause: RawGenericWhereClauseSyntax?
     if self.at(.keyword(.where)) {
       whereClause = self.parseGenericWhereClause()
@@ -1078,6 +1086,7 @@ extension Parser {
       optionalMark: failable,
       genericParameterClause: generics,
       signature: signature,
+      unexpectedResultType,
       genericWhereClause: whereClause,
       body: items,
       arena: self.arena

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -748,6 +748,33 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: InitializerDeclSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+
+    if let unexpectedName = node.signature.input.unexpectedBeforeLeftParen {
+      addDiagnostic(
+        unexpectedName,
+        .initializerCannotHaveName,
+        fixIts: [
+          FixIt(message: RemoveNodesFixIt(unexpectedName), changes: .makeMissing(unexpectedName))
+        ],
+        handledNodes: [unexpectedName.id]
+      )
+    }
+
+    if let unexpectedOutput = node.unexpectedBetweenSignatureAndGenericWhereClause {
+      addDiagnostic(
+        unexpectedOutput,
+        .initializerCannotHaveResultType,
+        handledNodes: [unexpectedOutput.id]
+      )
+    }
+
+    return .visitChildren
+  }
+
   public override func visit(_ node: MemberDeclListItemSyntax) -> SyntaxVisitorContinueKind {
     if shouldSkip(node) {
       return .skipChildren

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -131,6 +131,12 @@ extension DiagnosticMessage where Self == StaticParserError {
   public static var initializerInPattern: Self {
     .init("unexpected initializer in pattern; did you mean to use '='?")
   }
+  public static var initializerCannotHaveName: Self {
+    .init("initializers cannot have a name")
+  }
+  public static var initializerCannotHaveResultType: Self {
+    .init("initializers cannot have a result type")
+  }
   public static var invalidFlagAfterPrecedenceGroupAssignment: Self {
     .init("expected 'true' or 'false' after 'assignment'")
   }