Rust: Make Element.toString non-recursive

Author: hvitved

misc/codegen/templates/ql_class.mustache

@@ -30,7 +30,11 @@ module Generated {
      * Gets the string representation of this element.
      */
     cached
-    final string toString() { result = this.toStringImpl() }
+    final string toString() {
+      result = this.toStringImpl() and
+      // recursion guard to prevent `toString` from being defined recursively
+      (exists(any(Element e).toStringImpl()) implies any())
+    }
 
     /**
      * INTERNAL: Do not use.

rust/ql/.generated.list

@@ -20,6 +20,7 @@ module Impl {
      * Returns a string suitable to be inserted into the name of the parent. Typically `"..."`,
      * but may be overridden by subclasses.
      */
+    pragma[nomagic]
     string toAbbreviatedString() { result = "..." }
 
     predicate isUnknown() { none() } // compatibility with test generation, to be fixed

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

@@ -24,6 +24,6 @@ module Impl {
    * ```
    */
   class Module extends Generated::Module {
-    override string toStringImpl() { result = "mod " + this.getName() }
+    override string toStringImpl() { result = "mod " + this.getName().getText() }
   }
 }

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

@@ -19,6 +19,6 @@ module Impl {
    * ```
    */
   class Use extends Generated::Use {
-    override string toStringImpl() { result = "use " + this.getUseTree() }
+    override string toStringImpl() { result = "use " + this.getUseTree().toAbbreviatedString() }
   }
 }

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

@@ -26,14 +26,28 @@ module Impl {
       result = strictconcat(int i | | this.toStringPart(i) order by i)
     }
 
-    private string toStringPart(int index) {
-      result = this.getPath().toStringImpl() and index = 0
-      or
+    private string toStringPartCommon(int index) {
       result = "::{...}" and this.hasUseTreeList() and index = 1
       or
       result = "::*" and this.isGlob() and index = 2
       or
       result = " as " + this.getRename().getName().getText() and index = 3
     }
+
+    private string toStringPart(int index) {
+      result = this.getPath().toStringImpl() and index = 0
+      or
+      result = this.toStringPartCommon(index)
+    }
+
+    override string toAbbreviatedString() {
+      result = strictconcat(int i | | this.toAbbreviatedStringPart(i) order by i)
+    }
+
+    private string toAbbreviatedStringPart(int index) {
+      result = this.getPath().toAbbreviatedString() and index = 0
+      or
+      result = this.toStringPartCommon(index)
+    }
   }
 }