Add diagnostic for unexpected second identifier

Author: kimdv

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -810,6 +810,19 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+    public override func visit(_ node: PatternBindingSyntax) -> SyntaxVisitorContinueKind {
+        if shouldSkip(node) {
+            return .skipChildren
+        }
+
+        if let unexpected = (node.pattern.as(TuplePatternSyntax.self)?.unexpectedBetweenElementsAndRightParen),
+            let previousToken = node.previousToken(viewMode: .sourceAccurate) {
+            addDiagnostic(unexpected, SpaceSeparatedIdentifiersError(alternativeName: "constant declaration", firstToken: previousToken, additionalTokens: []))
+        }
+
+        return .visitChildren
+    }
+
   public override func visit(_ node: PrecedenceGroupAssignmentSyntax) -> SyntaxVisitorContinueKind {
     if shouldSkip(node) {
       return .skipChildren

Tests/SwiftParserTest/translated/RecoveryTests.swift

@@ -828,7 +828,7 @@ final class RecoveryTests: XCTestCase {
       """,
       diagnostics: [
         // TODO: (good first issue) Old parser expected error on line 1: found an unexpected second identifier in constant declaration; is there an accidental break?
-        DiagnosticSpec(message: "unexpected code 'hij, foobar' in tuple pattern")
+        DiagnosticSpec(message: "found an unexpected second identifier in variable")
       ]
     )
   }