Rust: Add ConstAccess class with getConst() predicate

rust/ql/lib/codeql/rust/elements/internal/ConstImpl.qll

@@ -6,6 +6,9 @@
  */
 
 private import codeql.rust.elements.internal.generated.Const
+private import codeql.rust.elements.PathExpr
+private import codeql.rust.elements.internal.PathExprBaseImpl::Impl as PathExprBaseImpl
+private import codeql.rust.internal.PathResolution
 
 /**
  * INTERNAL: This module contains the customizable definition of `Const` and should not
@@ -21,4 +24,34 @@ module Impl {
    * ```
    */
   class Const extends Generated::Const { }
+
+  /**
+   * A constant access.
+   *
+   * For example:
+   * ```rust
+   * const X: i32 = 42;
+   *
+   * fn main() {
+   *     println!("{}", X);
+   * }
+   * ```
+   */
+  class ConstAccess extends PathExprBaseImpl::PathExprBase {
+    private Const c;
+
+    ConstAccess() {
+      exists(PathExpr pe |
+        pe = this and
+        c = resolvePath(pe.getPath())
+      )
+    }
+
+    /** Gets the constant being accessed. */
+    Const getConst() { result = c }
+
+    override string toStringImpl() { result = c.getName().getText() }
+
+    override string getAPrimaryQlClass() { result = "ConstAccess" }
+  }
 }

rust/ql/test/library-tests/const_access/const_access.ql

@@ -0,0 +1,23 @@
+import rust
+import utils.test.InlineExpectationsTest
+import TestUtils
+
+query predicate constAccess(ConstAccess ca, Const c) {
+  toBeTested(ca) and c = ca.getConst()
+}
+
+module ConstAccessTest implements TestSig {
+  string getARelevantTag() { result = "const_access" }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(ConstAccess ca |
+      toBeTested(ca) and
+      location = ca.getLocation() and
+      element = ca.toString() and
+      tag = "const_access" and
+      value = ca.getConst().getName().getText()
+    )
+  }
+}
+
+import MakeTest<ConstAccessTest>

rust/ql/test/library-tests/const_access/main.rs

@@ -0,0 +1,42 @@
+const GLOBAL_CONST: i32 = 42;
+const STRING_CONST: &str = "hello";
+
+struct MyStruct {
+    value: i32,
+}
+
+impl MyStruct {
+    const ASSOC_CONST: i32 = 100;
+}
+
+mod my_module {
+    pub const MODULE_CONST: i32 = 200;
+}
+
+fn use_consts() {
+    // $ const_access=GLOBAL_CONST
+    let x = GLOBAL_CONST;
+    // $ const_access=GLOBAL_CONST
+    println!("{}", GLOBAL_CONST);
+
+    // $ const_access=STRING_CONST
+    let s = STRING_CONST;
+
+    // $ const_access=ASSOC_CONST
+    let y = MyStruct::ASSOC_CONST;
+
+    // $ const_access=MODULE_CONST
+    let z = my_module::MODULE_CONST;
+
+    // $ const_access=GLOBAL_CONST
+    if GLOBAL_CONST > 0 {
+        println!("positive");
+    }
+
+    // $ const_access=ASSOC_CONST
+    let arr = [MyStruct::ASSOC_CONST; 5];
+}
+
+fn main() {
+    use_consts();
+}