Add diagnostic if #endif is followed by any declarations

Author: kimdv

Sources/SwiftParser/Directives.swift

@@ -163,10 +163,21 @@ extension Parser {
     }
 
     let (unexpectedBeforePoundEndIf, poundEndIf) = self.expect(.poundEndifKeyword)
+    var unexpectedAfterPoundEndif: RawUnexpectedNodesSyntax?
+    if !self.currentToken.isAtStartOfLine {
+      var unexpectedTokens = [RawTokenSyntax]()
+      var loopProgress = LoopProgressCondition()
+      while !self.at(.eof), !currentToken.isAtStartOfLine, loopProgress.evaluate(self.currentToken) {
+        unexpectedTokens += [self.consumeAnyToken()]
+      }
+
+      unexpectedAfterPoundEndif = RawUnexpectedNodesSyntax(unexpectedTokens, arena: self.arena)
+    }
     return RawIfConfigDeclSyntax(
       clauses: RawIfConfigClauseListSyntax(elements: clauses, arena: self.arena),
       unexpectedBeforePoundEndIf,
       poundEndif: poundEndIf,
+      unexpectedAfterPoundEndif,
       arena: self.arena
     )
   }

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1136,6 +1136,15 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
         }
       }
     }
+
+    if let unexpectedAfterPoundEndif = node.unexpectedAfterPoundEndif {
+      addDiagnostic(
+        unexpectedAfterPoundEndif,
+        .extraTokensFollowingConditionalCompilationDirective,
+        handledNodes: [unexpectedAfterPoundEndif.id]
+      )
+    }
+
     return .visitChildren
   }
 

Sources/SwiftParserDiagnostics/ParserDiagnosticMessages.swift

@@ -156,6 +156,9 @@ extension DiagnosticMessage where Self == StaticParserError {
   public static var expectedSequenceExpressionInForEachLoop: Self {
     .init("expected Sequence expression for for-each loop")
   }
+  public static var extraTokensFollowingConditionalCompilationDirective: Self {
+    .init("extra tokens following conditional compilation directive")
+  }
   public static var extraRightBracket: Self {
     .init("unexpected ']' in type; did you mean to write an array type?")
   }

Tests/SwiftParserTest/DirectiveTests.swift

@@ -197,4 +197,20 @@ final class DirectiveTests: XCTestCase {
     )
   }
 
+  func testFollowedByDeclarations() {
+    assertParse(
+      """
+      struct Foo {
+        #if false
+        var x: Int
+      #endif1️⃣; var x = 1
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(
+          message: "extra tokens following conditional compilation directive"
+        )
+      ]
+    )
+  }
 }