Shared: Add Option types with location

shared/util/change-notes/2025-08-25-loc-option.md

@@ -0,0 +1,4 @@
+---
+* category: minorAnalysis
+---
+* Added `LocatableOption` and `OptionWithLocationInfo` as modules providing option types with location information.

shared/util/codeql/util/Option.qll

@@ -2,12 +2,24 @@
 overlay[local?]
 module;
 
+private import Location
+
 /** A type with `toString`. */
 private signature class TypeWithToString {
   bindingset[this]
   string toString();
 }
 
+/** A type with `toString` and `hasLocationInfo` */
+private signature class TypeWithLocationInfo {
+  bindingset[this]
+  string toString();
+
+  predicate hasLocationInfo(
+    string filePath, int startLine, int startColumn, int endLine, int endColumn
+  );
+}
+
 /**
  * Constructs an `Option` type that is a disjoint union of the given type and an
  * additional singleton element.
@@ -45,3 +57,91 @@ module Option<TypeWithToString T> {
   /** Gets the given element wrapped as an `Option`. */
   Some some(T c) { result = TSome(c) }
 }
+
+/**
+ * Constructs an `Option` type that is a disjoint union of the given type and an
+ * additional singleton element, and has a `hasLocationInfo` predicate.
+ * `T` must have a `hasLocationInfo` predicate.
+ */
+module OptionWithLocationInfo<TypeWithLocationInfo T> {
+  private module O = Option<T>;
+
+  final private class BaseOption = O::Option;
+
+  /**
+   * An option type. This is either a singleton `None` or a `Some` wrapping the
+   * given type.
+   */
+  class Option extends BaseOption {
+    /**
+     * Holds if this element is at the specified location.
+     * The location spans column `startColumn` of line `startLine` to
+     * column `endColumn` of line `endLine` in file `filepath`.
+     * For more information, see
+     * [Providing locations in CodeQL queries](https://codeql.github.com/docs/writing-codeql-queries/providing-locations-in-codeql-queries/).
+     */
+    predicate hasLocationInfo(
+      string filePath, int startLine, int startColumn, int endLine, int endColumn
+    ) {
+      this.isNone() and
+      filePath = "" and
+      startLine = 0 and
+      startColumn = 0 and
+      endLine = 0 and
+      endColumn = 0
+      or
+      this.asSome().hasLocationInfo(filePath, startLine, startColumn, endLine, endColumn)
+    }
+  }
+
+  /** The singleton `None` element. */
+  class None extends Option instanceof O::None { }
+
+  /** A wrapper for the given type. */
+  class Some extends Option instanceof O::Some { }
+
+  /** Gets the given element wrapped as an `Option`. */
+  Some some(T c) { result.asSome() = c }
+}
+
+private module WithLocation<LocationSig Location> {
+  signature class LocatableType {
+    bindingset[this]
+    string toString();
+
+    Location getLocation();
+  }
+}
+
+/**
+ * Constructs an `Option` type that is a disjoint union of the given type and an
+ * additional singleton element, and has a `getLocation` predicate.
+ * `T` must have a `getLocation` predicate with a result type of `Location`.
+ */
+module LocatableOption<LocationSig Location, WithLocation<Location>::LocatableType T> {
+  private module O = Option<T>;
+
+  final private class BaseOption = O::Option;
+
+  /**
+   * An option type. This is either a singleton `None` or a `Some` wrapping the
+   * given type.
+   */
+  class Option extends BaseOption {
+    Location getLocation() {
+      result = this.asSome().getLocation()
+      or
+      this.isNone() and
+      result.hasLocationInfo("", 0, 0, 0, 0)
+    }
+  }
+
+  /** The singleton `None` element. */
+  class None extends Option instanceof O::None { }
+
+  /** A wrapper for the given type. */
+  class Some extends Option instanceof O::Some { }
+
+  /** Gets the given element wrapped as an `Option`. */
+  Some some(T c) { result.asSome() = c }
+}