Rust: Add abstraction over all kinds of calls

rust/ql/lib/codeql/rust/controlflow/CfgNodes.qll

@@ -4,6 +4,7 @@
  */
 
 private import rust
+private import codeql.rust.elements.Call
 private import ControlFlowGraph
 private import internal.ControlFlowGraphImpl as CfgImpl
 private import internal.CfgNodes
@@ -162,6 +163,30 @@ final class CallExprBaseCfgNode extends Nodes::CallExprBaseCfgNode {
  */
 final class MethodCallExprCfgNode extends CallExprBaseCfgNode, Nodes::MethodCallExprCfgNode { }
 
+/**
+ * A CFG node that calls a function.
+ *
+ * This class abstract over the different ways in which a function can be called in Rust.
+ */
+final class CallCfgNode extends ExprCfgNode {
+  private Call node;
+
+  CallCfgNode() { node = this.getAstNode() }
+
+  /** Gets the underlying `Call`. */
+  Call getCall() { result = node }
+
+  /** Gets the receiver of this call if it is a method call. */
+  ExprCfgNode getReceiver() {
+    any(ChildMapping mapping).hasCfgChild(node, node.getReceiver(), this, result)
+  }
+
+  /** Gets the `i`th argument of this call, if any. */
+  ExprCfgNode getArgument(int i) {
+    any(ChildMapping mapping).hasCfgChild(node, node.getArgument(i), this, result)
+  }
+}
+
 /**
  * A function call expression. For example:
  * ```rust

rust/ql/lib/codeql/rust/elements/Call.qll

@@ -0,0 +1,7 @@
+/**
+ * Call.
+ */
+
+private import internal.CallImpl
+
+final class Call = Impl::Call;

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

@@ -0,0 +1,128 @@
+private import rust
+private import codeql.rust.internal.PathResolution
+private import codeql.rust.internal.TypeInference as TypeInference
+private import codeql.rust.elements.internal.ExprImpl::Impl as ExprImpl
+private import codeql.rust.elements.Operation
+
+module Impl {
+  /**
+   * An expression that calls a function.
+   *
+   * This class abstract over the different ways in which a function can be called in Rust.
+   */
+  abstract class Call extends ExprImpl::Expr {
+    Call() { this.fromSource() }
+
+    /** Gets the number of arguments _excluding_ any `self` argument. */
+    abstract int getNumberOfArguments();
+
+    /** Gets the receiver of this call if it is a method call. */
+    abstract Expr getReceiver();
+
+    /** Holds if the call has a receiver that might be implicitly borrowed. */
+    abstract predicate receiverImplicitlyBorrowed();
+
+    /** Gets the trait targeted by this call, if any. */
+    abstract Trait getTrait();
+
+    /** Gets the name of the method called if this call is a method call. */
+    abstract string getMethodName();
+
+    /** Gets the `i`th argument of this call, if any. */
+    abstract Expr getArgument(int i);
+
+    /** Gets the static target of this call, if any. */
+    Function getStaticTarget() {
+      result = TypeInference::resolveMethodCallTarget(this)
+      or
+      not exists(TypeInference::resolveMethodCallTarget(this)) and
+      result = this.(CallExpr).getStaticTarget()
+    }
+  }
+
+  /** Holds if the call expression dispatches to a trait method. */
+  private predicate callIsMethodCall(CallExpr call, Path qualifier, string methodName) {
+    exists(Path path, Function f |
+      path = call.getFunction().(PathExpr).getPath() and
+      f = resolvePath(path) and
+      f.getParamList().hasSelfParam() and
+      qualifier = path.getQualifier() and
+      path.getSegment().getIdentifier().getText() = methodName
+    )
+  }
+
+  private class CallExprCall extends Call instanceof CallExpr {
+    CallExprCall() { not callIsMethodCall(this, _, _) }
+
+    override string getMethodName() { none() }
+
+    override Expr getReceiver() { none() }
+
+    override Trait getTrait() { none() }
+
+    override predicate receiverImplicitlyBorrowed() { none() }
+
+    override int getNumberOfArguments() { result = super.getArgList().getNumberOfArgs() }
+
+    override Expr getArgument(int i) { result = super.getArgList().getArg(i) }
+  }
+
+  private class CallExprMethodCall extends Call instanceof CallExpr {
+    Path qualifier;
+    string methodName;
+
+    CallExprMethodCall() { callIsMethodCall(this, qualifier, methodName) }
+
+    override string getMethodName() { result = methodName }
+
+    override Expr getReceiver() { result = super.getArgList().getArg(0) }
+
+    override Trait getTrait() {
+      result = resolvePath(qualifier) and
+      // When the qualifier is `Self` and resolves to a trait, it's inside a
+      // trait method's default implementation. This is not a dispatch whose
+      // target is inferred from the type of the receiver, but should always
+      // resolve to the function in the trait block as path resolution does.
+      qualifier.toString() != "Self"
+    }
+
+    override predicate receiverImplicitlyBorrowed() { none() }
+
+    override int getNumberOfArguments() { result = super.getArgList().getNumberOfArgs() - 1 }
+
+    override Expr getArgument(int i) { result = super.getArgList().getArg(i + 1) }
+  }
+
+  private class MethodCallExprCall extends Call instanceof MethodCallExpr {
+    override string getMethodName() { result = super.getIdentifier().getText() }
+
+    override Expr getReceiver() { result = this.(MethodCallExpr).getReceiver() }
+
+    override Trait getTrait() { none() }
+
+    override predicate receiverImplicitlyBorrowed() { any() }
+
+    override int getNumberOfArguments() { result = super.getArgList().getNumberOfArgs() }
+
+    override Expr getArgument(int i) { result = super.getArgList().getArg(i) }
+  }
+
+  private class OperatorCall extends Call instanceof Operation {
+    Trait trait;
+    string methodName;
+
+    OperatorCall() { super.isOverloaded(trait, methodName) }
+
+    override string getMethodName() { result = methodName }
+
+    override Expr getReceiver() { result = super.getOperand(0) }
+
+    override Trait getTrait() { result = trait }
+
+    override predicate receiverImplicitlyBorrowed() { none() }
+
+    override int getNumberOfArguments() { result = super.getNumberOfOperands() - 1 }
+
+    override Expr getArgument(int i) { result = super.getOperand(1) and i = 0 }
+  }
+}