Add diagnostic if #if is followed by any declarations

Author: kimdv

Sources/SwiftParser/Directives.swift

@@ -106,12 +106,14 @@ extension Parser {
     // Parse #if
     let (unexpectedBeforePoundIfKeyword, poundIfKeyword) = self.expect(.poundIfKeyword)
     let condition = RawExprSyntax(self.parseSequenceExpression(.basic, forDirective: true))
+    let unexpectedBetweenConditionAndElements = self.consumeRemainingTokenOnLine()
 
     clauses.append(
       RawIfConfigClauseSyntax(
         unexpectedBeforePoundIfKeyword,
         poundKeyword: poundIfKeyword,
         condition: condition,
+        unexpectedBetweenConditionAndElements,
         elements: syntax(&self, parseIfConfigClauseElements(parseElement, addSemicolonIfNeeded: addSemicolonIfNeeded)),
         arena: self.arena
       )
@@ -272,20 +274,4 @@ extension Parser {
       arena: self.arena
     )
   }
-
-  /// Consumes remaining token on the line and returns a ``RawUnexpectedNodesSyntax``
-  /// if there is any tokens consumed.
-  private mutating func consumeRemainingTokenOnLine() -> RawUnexpectedNodesSyntax? {
-    guard !self.currentToken.isAtStartOfLine else {
-      return nil
-    }
-
-    var unexpectedTokens = [RawTokenSyntax]()
-    var loopProgress = LoopProgressCondition()
-    while !self.at(.eof), !currentToken.isAtStartOfLine, loopProgress.evaluate(self.currentToken) {
-      unexpectedTokens += [self.consumeAnyToken()]
-    }
-
-    return RawUnexpectedNodesSyntax(unexpectedTokens, arena: self.arena)
-  }
 }

Sources/SwiftParser/Parser.swift

@@ -257,6 +257,22 @@ extension Parser {
     return self.consumeAnyToken()
   }
 
+  /// Consumes remaining token on the line and returns a ``RawUnexpectedNodesSyntax``
+  /// if there is any tokens consumed.
+  mutating func consumeRemainingTokenOnLine() -> RawUnexpectedNodesSyntax? {
+    guard !self.currentToken.isAtStartOfLine else {
+      return nil
+    }
+
+    var unexpectedTokens = [RawTokenSyntax]()
+    var loopProgress = LoopProgressCondition()
+    while !self.at(.eof), !currentToken.isAtStartOfLine, loopProgress.evaluate(self.currentToken) {
+      unexpectedTokens += [self.consumeAnyToken()]
+    }
+
+    return RawUnexpectedNodesSyntax(unexpectedTokens, arena: self.arena)
+  }
+
 }
 
 // MARK: Check if we can recover to a token

Sources/SwiftParserDiagnostics/ParseDiagnosticsGenerator.swift

@@ -1100,6 +1100,22 @@ public class ParseDiagnosticsGenerator: SyntaxAnyVisitor {
     return .visitChildren
   }
 
+  public override func visit(_ node: IfConfigClauseSyntax) -> SyntaxVisitorContinueKind {
+    if shouldSkip(node) {
+      return .skipChildren
+    }
+
+    if let unexpectedBetweenConditionAndElements = node.unexpectedBetweenConditionAndElements {
+      addDiagnostic(
+        unexpectedBetweenConditionAndElements,
+        .extraTokensFollowingConditionalCompilationDirective,
+        handledNodes: [unexpectedBetweenConditionAndElements.id]
+      )
+    }
+
+    return .visitChildren
+  }
+
   public override func visit(_ node: IfConfigDeclSyntax) -> SyntaxVisitorContinueKind {
     for clause in node.clauses where clause.hasError {
       if let unexpectedBeforePoundKeyword = clause.unexpectedBeforePoundKeyword,

Tests/SwiftParserTest/DirectiveTests.swift

@@ -197,13 +197,45 @@ final class DirectiveTests: XCTestCase {
     )
   }
 
-  func testFollowedByDeclarations() {
+  func testEndIfFollowedByDeclarations() {
     assertParse(
       """
       struct Foo {
         #if false
         var x: Int
-      #endif1️⃣; var x = 1
+        #endif1️⃣; var x = 1
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(
+          message: "extra tokens following conditional compilation directive"
+        )
+      ]
+    )
+  }
+
+  func testIfFollowByDeclarations() {
+    assertParse(
+      """
+      struct Foo {
+        #if DEBUG1️⃣; var x = 1
+        var x: Int
+        #endif
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(
+          message: "extra tokens following conditional compilation directive"
+        )
+      ]
+    )
+
+    assertParse(
+      """
+      struct Foo {
+        #if DEBUG || UAT1️⃣; var x = 1
+        var x: Int
+        #endif
       }
       """,
       diagnostics: [