Shared: Add Util qlpack.

Author: aschackmull

shared/util/change-notes/2022-11-30-initial-version.md

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+---
+category: minorAnalysis
+---
+* Initial release. Includes common utility classes and modules: Unit, Boolean, and Option.

shared/util/codeql/util/Boolean.qll

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+/** Provides the `Boolean` class. */
+
+/**
+ * A utility class that is equivalent to `boolean`.
+ *
+ * As opposed to `boolean`, this type does not require explicit binding.
+ */
+class Boolean extends boolean {
+  Boolean() { this = [true, false] }
+}

shared/util/codeql/util/Option.qll

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+/** Provides a module for constructing optional versions of types. */
+
+/** A type with `toString`. */
+signature class TypeWithToString {
+  string toString();
+}
+
+/**
+ * Constructs an `Option` type that is a disjoint union of the given type and an
+ * additional singleton element.
+ */
+module Option<TypeWithToString T> {
+  private newtype TOption =
+    TNone() or
+    TSome(T c)
+
+  /**
+   * An option type. This is either a singleton `None` or a `Some` wrapping the
+   * given type.
+   */
+  class Option extends TOption {
+    /** Gets a textual representation of this element. */
+    string toString() {
+      this = TNone() and result = "(none)"
+      or
+      exists(T c | this = TSome(c) and result = c.toString())
+    }
+
+    /** Gets the wrapped element, if any. */
+    T asSome() { this = TSome(result) }
+  }
+
+  /** The singleton `None` element. */
+  class None extends Option, TNone { }
+
+  /** A wrapper for the given type. */
+  class Some extends Option, TSome { }
+
+  /** Gets the given element wrapped as an `Option`. */
+  Some some(T c) { result = TSome(c) }
+}

shared/util/codeql/util/Unit.qll

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+/** Provides the `Unit` class. */
+
+/** The unit type. */
+private newtype TUnit = TMkUnit()
+
+/** The trivial type with a single element. */
+class Unit extends TUnit {
+  /** Gets a textual representation of this element. */
+  string toString() { result = "unit" }
+}

shared/util/qlpack.yml

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+name: codeql/util
+version: 0.0.1-dev
+groups: shared
+library: true
+dependencies: