Add diagnostic for wrong inheritance

Author: kimdv

Sources/SwiftParser/Nominals.swift

@@ -180,7 +180,7 @@ extension Parser {
     }
 
     let inheritance: RawTypeInheritanceClauseSyntax?
-    if self.at(.colon) {
+    if self.at(.colon) || self.at(.leftParen) {
       inheritance = self.parseInheritance()
     } else {
       inheritance = nil
@@ -213,7 +213,16 @@ extension Parser {
   /// Parse an inheritance clause.
   @_spi(RawSyntax)
   public mutating func parseInheritance() -> RawTypeInheritanceClauseSyntax {
-    let (unexpectedBeforeColon, colon) = self.expect(.colon)
+      let unexpectedBeforeColon: RawUnexpectedNodesSyntax?
+      let colon: RawTokenSyntax
+      if self.at(.colon) {
+          unexpectedBeforeColon = nil
+          colon = consumeAnyToken(remapping: .colon)
+      } else {
+          unexpectedBeforeColon = RawUnexpectedNodesSyntax([self.consumeAnyToken()], arena: self.arena)
+          colon = missingToken(.colon)
+      }
+
     var elements = [RawInheritedTypeSyntax]()
     do {
       var keepGoing: RawTokenSyntax? = nil
@@ -241,6 +250,7 @@ extension Parser {
         )
       } while keepGoing != nil && loopProgress.evaluate(currentToken)
     }
+
     return RawTypeInheritanceClauseSyntax(
       unexpectedBeforeColon,
       colon: colon,

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1171,7 +1171,26 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return handleEffectSpecifiers(node)
   }
 
-  public override func visit(_ node: TypeInitializerClauseSyntax) -> SyntaxVisitorContinueKind {
+
+
+    public override func visit(_ node: TypeInheritanceClauseSyntax) -> SyntaxVisitorContinueKind {
+        if shouldSkip(node) {
+            return .skipChildren
+        }
+
+        if let unexpected = node.unexpectedBeforeColon, !unexpected.tokens(satisfying: { $0.tokenKind == .leftParen }).isEmpty {
+            addDiagnostic(unexpected,
+                .expectedColonClass,
+                          fixIts: [FixIt(message: <#T##FixItMessage#>,
+                                         changes: [FixIt.Changes.makePresent(node.colon), .makeMissing(unexpected)])],
+                          handledNodes: [unexpected.id, node.colon.id]
+            )
+        }
+
+        return .visitChildren
+    }
+
+    public override func visit(_ node: TypeInitializerClauseSyntax) -> SyntaxVisitorContinueKind {
     if shouldSkip(node) {
       return .skipChildren
     }

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -125,6 +125,9 @@ extension DiagnosticMessage where Self == StaticParserError {
   public static var escapedNewlineAtLatlineOfMultiLineStringLiteralNotAllowed: Self {
     .init("escaped newline at the last line of a multi-line string literal is not allowed")
   }
+    public static var expectedColonClass: Self {
+        .init("expected ':' to begin inheritance clause")
+    }
   public static var expectedExpressionAfterTry: Self {
     .init("expected expression after 'try'")
   }