[ASTGen] Update for UnexpectedCodeDeclSyntax addition

lib/ASTGen/Sources/ASTGen/Decls.swift

@@ -67,6 +67,9 @@ extension ASTGenVisitor {
       return self.generate(subscriptDecl: node).asDecl
     case .typeAliasDecl(let node):
       return self.generate(typeAliasDecl: node)?.asDecl
+    case .unexpectedCodeDecl:
+      // Ignore unexpected code.
+      return nil
     case .variableDecl(let node):
       return self.generate(variableDecl: node)
     case .usingDecl(let node):

test/ASTGen/if_config_expr.swift

@@ -46,7 +46,7 @@ func testInvalidContent(baseExpr: MyStruct, otherExpr: Int) {
 
   baseExpr      // expected-warning {{expression of type 'MyStruct' is unused}}
 #if CONDITION_1
-    + otherExpr // expected-error {{unexpected code '+ otherExpr' in conditional compilation block}}
+    + otherExpr // expected-error {{unexpected code '+ otherExpr' in conditional compilation clause}}
 #endif
 
   baseExpr