Rust: Remove elements superseded by attribute macro expansions

Author: hvitved

rust/ql/.generated.list

@@ -13,9 +13,9 @@ private import codeql.rust.controlflow.ControlFlowGraph
  */
 module Impl {
   private import rust
+  private import codeql.rust.elements.internal.ElementImpl::Impl as ElementImpl
   private import codeql.rust.elements.internal.generated.ParentChild
   private import codeql.rust.controlflow.ControlFlowGraph
-  private import codeql.rust.elements.internal.MacroCallImpl::Impl as MacroCallImpl
 
   /**
    * Gets the immediate parent of a non-`AstNode` element `e`.
@@ -71,21 +71,15 @@ module Impl {
     }
 
     /** Holds if this node is inside a macro expansion. */
-    predicate isInMacroExpansion() { MacroCallImpl::isInMacroExpansion(_, this) }
+    predicate isInMacroExpansion() { ElementImpl::MacroExpansion::isInMacroExpansion(this) }
 
     /**
      * Holds if this node exists only as the result of a macro expansion.
      *
      * This is the same as `isInMacroExpansion()`, but excludes AST nodes corresponding
-     * to macro arguments.
+     * to macro arguments, including attribute macro targets.
      */
-    pragma[nomagic]
-    predicate isFromMacroExpansion() {
-      exists(AstNode root |
-        MacroCallImpl::isInMacroExpansion(root, this) and
-        not this = root.(MacroCall).getATokenTreeNode()
-      )
-    }
+    predicate isFromMacroExpansion() { ElementImpl::MacroExpansion::isFromMacroExpansion(this) }
 
     /**
      * Gets a control flow node for this AST node, if any.

rust/ql/.gitattributes

@@ -11,7 +11,118 @@ private import codeql.rust.elements.internal.generated.Element
  * be referenced directly.
  */
 module Impl {
+  private import rust
+  private import codeql.rust.elements.internal.generated.ParentChild
+  private import codeql.rust.elements.internal.generated.Synth
+  private import codeql.rust.elements.internal.generated.Raw
+  private import codeql.rust.elements.internal.LocationImpl
+
+  /**
+   * Provides logic for classifying elements with respect to macro expansions.
+   */
+  cached
+  module MacroExpansion {
+    /**
+     * Holds if `e` is superseded by an attribute macro expansion. That is, `e` is
+     * a transitive child of an item with an attribute macro expansion.
+     *
+     * Since this predicate is referenced in the charpred of `Element`, we need to
+     * use the parent-child relation on raw elements to avoid non-monotonicity.
+     */
+    private predicate supersededByAttributeMacroExpansionRaw(Raw::Item item, Raw::Element e) {
+      exists(item.getAttributeMacroExpansion()) and
+      e = Raw::getImmediateChild(item, _) and
+      not e = item.getAttributeMacroExpansion() and
+      // Don't consider attributes themselves to be superseded.  E.g., in `#[a] fn
+      // f() {}` the macro expansion supersedes `fn f() {}` but not `#[a]`.
+      not e instanceof Raw::Attr
+      or
+      exists(Raw::Element parent |
+        e = Raw::getImmediateChild(parent, _) and
+        supersededByAttributeMacroExpansionRaw(item, parent)
+      )
+    }
+
+    private predicate isMacroExpansion(AstNode macro, AstNode expansion) {
+      expansion = macro.(MacroCall).getMacroCallExpansion()
+      or
+      expansion = macro.(Adt).getDeriveMacroExpansion(_)
+      or
+      expansion = macro.(Item).getAttributeMacroExpansion()
+    }
+
+    /**
+     * Gets the immediately enclosing macro invocation for element `e`, if any.
+     *
+     * The result is either a `MacroCall`, and `Adt` with a derive macro expansion, or
+     * an `Item` with an attribute macro expansion.
+     */
+    cached
+    AstNode getImmediatelyEnclosingMacroInvocation(Element e) {
+      isMacroExpansion(result, e)
+      or
+      exists(Element mid |
+        result = getImmediatelyEnclosingMacroInvocation(mid) and
+        mid = getImmediateParent(e) and
+        not isMacroExpansion(mid, e)
+      )
+    }
+
+    pragma[nomagic]
+    private predicate isAttributeMacroExpansionSourceLocation(Item i, Location l) {
+      exists(Raw::Locatable e, @location_default loc |
+        supersededByAttributeMacroExpansionRaw(Synth::convertElementToRaw(i), e) and
+        locatable_locations(e, loc) and
+        l = LocationImpl::TLocationDefault(loc)
+      )
+    }
+
+    /** Gets an AST node whose location is inside the token tree belonging to `mc`. */
+    pragma[nomagic]
+    private AstNode getATokenTreeNode(MacroCall mc) {
+      mc = getImmediatelyEnclosingMacroInvocation(result) and
+      mc.getTokenTree().getLocation().contains(result.getLocation())
+    }
+
+    /** Holds if `n` is inside a macro expansion. */
+    cached
+    predicate isInMacroExpansion(AstNode n) { exists(getImmediatelyEnclosingMacroInvocation(n)) }
+
+    /**
+     * Holds if `n` exists only as the result of a macro expansion.
+     *
+     * This is the same as `isInMacroExpansion(n)`, but excludes AST nodes corresponding
+     * to macro arguments, including attribute macro targets.
+     *
+     * Note: This predicate is a heuristic based on location information and may not be
+     * accurate in all cases.
+     */
+    cached
+    predicate isFromMacroExpansion(AstNode n) {
+      exists(AstNode macro |
+        macro = getImmediatelyEnclosingMacroInvocation(n) and
+        not n = getATokenTreeNode(macro) and
+        not isAttributeMacroExpansionSourceLocation(macro, n.getLocation())
+      )
+      or
+      isFromMacroExpansion(getImmediatelyEnclosingMacroInvocation(n))
+    }
+
+    cached
+    predicate isRelevantElement(Generated::Element e) {
+      exists(Raw::Element raw |
+        raw = Synth::convertElementToRaw(e) and
+        not supersededByAttributeMacroExpansionRaw(_, raw)
+      )
+      or
+      // Synthetic elements are relevant when their parents are
+      Synth::convertFormatArgsExprToRaw(_) = Synth::getSynthParent(e)
+    }
+  }
+
   class Element extends Generated::Element {
+    Element() { MacroExpansion::isRelevantElement(this) }
+
     override string toStringImpl() { result = this.getAPrimaryQlClass() }
 
     /**

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

@@ -1,4 +1,3 @@
-// generated by codegen, remove this comment if you wish to edit this file
 /**
  * This module provides a hand-modifiable wrapper around the generated class `Item`.
  *
@@ -12,6 +11,7 @@ private import codeql.rust.elements.internal.generated.Item
  * be referenced directly.
  */
 module Impl {
+  // the following QLdoc is generated: if you need to edit it, do it in the schema file
   /**
    * An item such as a function, struct, enum, etc.
    *
@@ -23,4 +23,10 @@ module Impl {
    * ```
    */
   class Item extends Generated::Item { }
+
+  private class ItemWithAttributeMacroExpansion extends Item {
+    ItemWithAttributeMacroExpansion() { this.hasAttributeMacroExpansion() }
+
+    override string toStringImpl() { result = "(item with attribute macro expansion)" }
+  }
 }

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

@@ -5,6 +5,7 @@
  */
 
 import codeql.Locations
+private import codeql.rust.elements.internal.ElementImpl::Impl as ElementImpl
 private import codeql.rust.elements.internal.LocationImpl
 private import codeql.rust.elements.internal.generated.Locatable
 private import codeql.rust.elements.internal.generated.Synth
@@ -50,21 +51,12 @@ module Impl {
     locatable_locations(Synth::convertLocatableToRaw(l), result)
   }
 
-  private MacroCall getImmediatelyEnclosingMacroCall(AstNode n) {
-    result = n.getParentNode()
-    or
-    exists(AstNode mid |
-      result = getImmediatelyEnclosingMacroCall(mid) and
-      n.getParentNode() = mid and
-      not mid instanceof MacroCall
-    )
-  }
-
   /** Gets the non-synthesized location of `l`, if any. */
   LocationImpl::LocationDefault getLocationDefault(Locatable l) {
     result = LocationImpl::TLocationDefault(getDbLocation(l))
     or
     not exists(getDbLocation(l)) and
-    result = getLocationDefault(getImmediatelyEnclosingMacroCall(l))
+    result =
+      getLocationDefault(ElementImpl::MacroExpansion::getImmediatelyEnclosingMacroInvocation(l))
   }
 }

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

@@ -14,17 +14,6 @@ module Impl {
   private import rust
   private import codeql.rust.internal.PathResolution
 
-  pragma[nomagic]
-  predicate isInMacroExpansion(AstNode root, AstNode n) {
-    n = root.(MacroCall).getMacroCallExpansion()
-    or
-    n = root.(Adt).getDeriveMacroExpansion(_)
-    or
-    n = root.(Item).getAttributeMacroExpansion()
-    or
-    isInMacroExpansion(root, n.getParentNode())
-  }
-
   // the following QLdoc is generated: if you need to edit it, do it in the schema file
   /**
    * A macro invocation.
@@ -35,16 +24,7 @@ module Impl {
    * ```
    */
   class MacroCall extends Generated::MacroCall {
-    override string toStringImpl() {
-      if this.hasPath() then result = this.getPath().toAbbreviatedString() + "!..." else result = ""
-    }
-
-    /** Gets an AST node whose location is inside the token tree belonging to this macro call. */
-    pragma[nomagic]
-    AstNode getATokenTreeNode() {
-      isInMacroExpansion(this, result) and
-      this.getTokenTree().getLocation().contains(result.getLocation())
-    }
+    override string toStringImpl() { result = this.getPath().toAbbreviatedString() + "!..." }
 
     /**
      * Gets the macro definition that this macro call resolves to.

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

@@ -90,24 +90,6 @@ private module UseOption = Option<Use>;
 
 private class UseOption = UseOption::Option;
 
-/**
- * Holds if `n` is superseded by an attribute macro expansion. That is, `n` is
- * an item or a transitive child of an item with an attribute macro expansion.
- */
-predicate supersededByAttributeMacroExpansion(AstNode n) {
-  n.(Item).hasAttributeMacroExpansion()
-  or
-  exists(AstNode parent |
-    n.getParentNode() = parent and
-    supersededByAttributeMacroExpansion(parent) and
-    // Don't exclude expansions themselves as they supercede other nodes.
-    not n = parent.(Item).getAttributeMacroExpansion() and
-    // Don't consider attributes themselves to be superseded.  E.g., in `#[a] fn
-    // f() {}` the macro expansion supercedes `fn f() {}` but not `#[a]`.
-    not n instanceof Attr
-  )
-}
-
 /**
  * An item that may be referred to by a path, and which is a node in
  * the _item graph_.
@@ -186,10 +168,7 @@ predicate supersededByAttributeMacroExpansion(AstNode n) {
  * - https://doc.rust-lang.org/reference/names/namespaces.html
  */
 abstract class ItemNode extends Locatable {
-  ItemNode() {
-    // Exclude items that are superseded by the expansion of an attribute macro.
-    not supersededByAttributeMacroExpansion(this)
-  }
+  ItemNode() { not this.(Item).hasAttributeMacroExpansion() }
 
   /** Gets the (original) name of this item. */
   abstract string getName();

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

@@ -10,9 +10,8 @@ private import utils.test.InlineExpectationsTest
 private module ResolveTest implements TestSig {
   string getARelevantTag() { result = "item" }
 
-  private predicate itemAt(ItemNode i, string filepath, int line, boolean inMacro) {
-    i.getLocation().hasLocationInfo(filepath, _, _, line, _) and
-    if i.(AstNode).isInMacroExpansion() then inMacro = true else inMacro = false
+  private predicate itemAt(ItemNode i, string filepath, int line) {
+    i.getLocation().hasLocationInfo(filepath, _, _, line, _)
   }
 
   private predicate commmentAt(string text, string filepath, int line) {
@@ -25,7 +24,7 @@ private module ResolveTest implements TestSig {
   }
 
   private predicate item(ItemNode i, string value) {
-    exists(string filepath, int line, boolean inMacro | itemAt(i, filepath, line, inMacro) |
+    exists(string filepath, int line | itemAt(i, filepath, line) |
       if i instanceof SourceFile
       then value = i.getFile().getBaseName()
       else (

rust/ql/lib/codeql/rust/internal/PathResolution.qll

@@ -33,7 +33,7 @@ predicate hiddenNode(AstNode n) {
   n instanceof ControlFlowGraphImpl::PostOrderTree and // location is counter-intuitive
   not n instanceof MacroExpr
   or
-  n.isInMacroExpansion()
+  n.isFromMacroExpansion()
 }
 
 /**