Swift: minor tweaks

Replace string singleton with a newtype-based one, and fix some doc
comment cosmetics.

Author: redsun82

swift/ql/lib/codeql/swift/printast/PrintAst.qll

@@ -5,18 +5,16 @@
 import swift
 import codeql.swift.generated.ParentChild
 
+private newtype TPrintAstConfiguration = TMakePrintAstConfiguration()
+
 /**
- * Hook to customize the files and functions printed by this module.
- *
- * For an AstNode to be printed, it always requires `shouldPrintFile(f)` to hold
- * for its containing file `f`, and additionally requires `shouldPrintFunction(fun)`
- * to hold if it is, or is a child of, function `fun`.
+ * The hook to customize the files and functions printed by this module.
  */
-class PrintAstConfiguration extends string {
+class PrintAstConfiguration extends TPrintAstConfiguration {
   /**
-   * Restrict to a single string, making this a singleton type.
+   * Gets the string representation of this singleton
    */
-  PrintAstConfiguration() { this = "PrintAstConfiguration" }
+  string toString() { result = "PrintAstConfiguration" }
 
   /**
    * Holds if the AST for `e` should be printed. By default, holds for all.

swift/ql/src/queries/ide-contextual-queries/printast.ql

@@ -12,14 +12,14 @@ import codeql.swift.printast.PrintAst
 import IDEContextual
 
 /**
- * The source file to generate an AST from.
+ * Gets the source file to generate an AST from.
  */
 external string selectedSourceFile();
 
 class PrintAstConfigurationOverride extends PrintAstConfiguration {
   /**
    * Holds if the location matches the selected file in the VS Code extension and
-   * the element is `fromSource`.
+   * the element is `e`.
    */
   override predicate shouldPrint(Locatable e) {
     super.shouldPrint(e) and

swift/ql/test/library-tests/ast/PrintAst.ql

@@ -7,7 +7,7 @@ import codeql.swift.printast.PrintAst
 import TestUtils
 
 /**
- * Hook to customize the functions printed by this query.
+ * The hook to customize the entities printed by this query.
  */
 class PrintAstConfigurationOverride extends PrintAstConfiguration {
   override predicate shouldPrint(Locatable e) { super.shouldPrint(e) and toBeTested(e) }