Test directives that come before the unit keyword

AST.DirectiveBeforeUnit parses a unit that starts with {$WARN ...} and
{$D+} and checks that both end up first under the ntUnit root, in source
order, and that the rest of the unit still parses. It fails on main and
passes with the fix.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: Partouf

Test/UnitTests/DelphiAST.Tests.pas

@@ -317,6 +317,26 @@ procedure TestUnicodeStringTypecast;
   end;
 end;
 
+procedure TestDirectiveBeforeUnit;
+var
+  Root: TSyntaxNode;
+begin
+  Root := ParseSource('{$WARN UNIT_PLATFORM OFF}' + sLineBreak + '{$D+}' + sLineBreak +
+    'unit Example; interface implementation end.');
+  try
+    AssertNotNil(Root, 'Missing root');
+    AssertTrue(Root.Typ = ntUnit, 'The root is the unit.');
+    AssertTrue(Root.ChildNodes[0].Typ = ntCompilerDirective, 'First directive under the root.');
+    AssertEquals('WARN', Root.ChildNodes[0].GetAttribute(anType), 'First directive, in source order.');
+    AssertEquals(1, Root.ChildNodes[0].Line, 'First directive line.');
+    AssertTrue(Root.ChildNodes[1].Typ = ntCompilerDirective, 'Second directive under the root.');
+    AssertEquals('D', Root.ChildNodes[1].GetAttribute(anType), 'Second directive, in source order.');
+    AssertNotNil(FindDescendant(Root, ntImplementation), 'The rest of the unit still parses.');
+  finally
+    Root.Free;
+  end;
+end;
+
 procedure TestInvalidSyntax;
 var
   Root: TSyntaxNode;
@@ -397,6 +417,7 @@ procedure RunAllTests;
   RunTest('Node.AttributeRemove', TestAttributeRemove);
   RunTest('AST.RepeatedCallingConvention', TestRepeatedCallingConvention);
   RunTest('AST.UnicodeStringTypecast', TestUnicodeStringTypecast);
+  RunTest('AST.DirectiveBeforeUnit', TestDirectiveBeforeUnit);
   RunTest('Parser.InvalidSyntax', TestInvalidSyntax);
   RunTest('Parser.UnexpectedEndOfFilePosition', TestUnexpectedEndOfFilePosition);
   {$IFNDEF FPC}