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Python: First stab at shared control-flow
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Taus
@@ -7,6 +7,7 @@ library: true
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upgrades: upgrades
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dependencies:
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codeql/concepts: ${workspace}
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codeql/controlflow: ${workspace}
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codeql/dataflow: ${workspace}
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codeql/mad: ${workspace}
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codeql/regex: ${workspace}
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376
python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll
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376
python/ql/lib/semmle/python/controlflow/internal/AstNodeImpl.qll
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@@ -0,0 +1,376 @@
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/**
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* Provides a newtype-based interface layer that mediates between the existing
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* Python AST classes and the shared control-flow library's `AstSig` signature.
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*
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* The newtype unifies Python's `Stmt`, `Expr`, `Scope`, and `StmtList` into a
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* single `AstNode` type. Notably, `StmtList` (which is not an `AstNode` in the
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* existing Python AST) is wrapped as a `BlockStmt` (a subtype of `Stmt`),
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* since the shared CFG library expects statement blocks to be statements.
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*/
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private import python as Py
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private import codeql.controlflow.ControlFlowGraph
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private module Ast {
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/** The newtype representing AST nodes for the shared CFG library. */
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private newtype TAstNode =
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TStmtNode(Py::Stmt s) or
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TExprNode(Py::Expr e) or
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TScopeNode(Py::Scope sc) or
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TStmtListNode(Py::StmtList sl)
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/**
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* An AST node for the shared CFG. Each branch of the newtype gets a
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* subclass that overrides `toString` and `getLocation`.
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*/
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class Node extends TAstNode {
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string toString() { none() }
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Py::Location getLocation() { none() }
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/** Gets the enclosing scope of this node, if any. */
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ScopeNode getEnclosingScope() { none() }
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}
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class StmtNode extends Node, TStmtNode {
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/** Gets the underlying Python statement. */
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Py::Stmt asStmt() { this = TStmtNode(result) }
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override string toString() { result = this.asStmt().toString() }
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override Py::Location getLocation() { result = this.asStmt().getLocation() }
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/** Gets the enclosing scope of this statement. */
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override ScopeNode getEnclosingScope() { result.asScope() = this.asStmt().getScope() }
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}
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class ExprNode extends Node, TExprNode {
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/** Gets the underlying Python expression. */
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Py::Expr asExpr() { this = TExprNode(result) }
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override string toString() { result = this.asExpr().toString() }
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override Py::Location getLocation() { result = this.asExpr().getLocation() }
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/** Gets the enclosing scope of this expression. */
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override ScopeNode getEnclosingScope() { result.asScope() = this.asExpr().getScope() }
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}
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class ScopeNode extends Node, TScopeNode {
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/** Gets the underlying Python scope. */
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Py::Scope asScope() { this = TScopeNode(result) }
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override string toString() { result = this.asScope().toString() }
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override Py::Location getLocation() { result = this.asScope().getLocation() }
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/** Gets the body of this scope. */
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StmtListNode getBody() { result.asStmtList() = this.asScope().getBody() }
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/** Gets the enclosing scope of this scope, if any. */
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override ScopeNode getEnclosingScope() { result.asScope() = this.asScope().getEnclosingScope() }
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}
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class StmtListNode extends Node, TStmtListNode {
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/** Gets the underlying Python statement list. */
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Py::StmtList asStmtList() { this = TStmtListNode(result) }
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override string toString() { result = this.asStmtList().toString() }
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// StmtList has no native location; approximate with first item's location.
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override Py::Location getLocation() { result = this.asStmtList().getItem(0).getLocation() }
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/** Gets the `n`th (zero-based) statement in this block. */
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StmtNode getItem(int n) { result.asStmt() = this.asStmtList().getItem(n) }
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/** Gets the last statement in this block. */
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StmtNode getLastItem() { result.asStmt() = this.asStmtList().getLastItem() }
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/** Gets the enclosing scope of this statement list. */
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override ScopeNode getEnclosingScope() {
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result.asScope() = this.asStmtList().getParent().(Py::Scope)
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or
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result.asScope() = this.asStmtList().getParent().(Py::Stmt).getScope()
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}
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}
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/** An `if` statement. */
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class IfNode extends StmtNode {
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private Py::If ifStmt;
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IfNode() { ifStmt = this.asStmt() }
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/** Gets the condition of this `if` statement. */
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ExprNode getTest() { result.asExpr() = ifStmt.getTest() }
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/** Gets the if-true branch. */
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StmtListNode getBody() { result.asStmtList() = ifStmt.getBody() }
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/** Gets the if-false branch, if any. */
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StmtListNode getOrelse() { result.asStmtList() = ifStmt.getOrelse() }
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}
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/** An expression statement. */
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class ExprStmtNode extends StmtNode {
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private Py::ExprStmt exprStmt;
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ExprStmtNode() { exprStmt = this.asStmt() }
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/** Gets the expression in this statement. */
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ExprNode getValue() { result.asExpr() = exprStmt.getValue() }
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}
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}
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/** Provides an implementation of the AST signature for Python. */
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module AstSigImpl implements AstSig<Py::Location> {
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class AstNode = Ast::Node;
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/** Gets the child of `n` at the specified (zero-based) index. */
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AstNode getChild(AstNode n, int index) {
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exists(Ast::IfNode ifNode | ifNode = n |
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index = 0 and result = ifNode.getTest()
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or
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index = 1 and result = ifNode.getBody()
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or
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index = 2 and result = ifNode.getOrelse()
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)
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or
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result = n.(Ast::StmtListNode).getItem(index)
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or
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index = 0 and result = n.(Ast::ExprStmtNode).getValue()
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}
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Callable getEnclosingCallable(AstNode node) { result = node.getEnclosingScope() }
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/**
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* A callable: a function, class, or module scope.
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*
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* In Python, all three are executable scopes with statement bodies.
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*/
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class Callable extends Ast::ScopeNode { }
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/** Gets the body of callable `c`. */
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AstNode callableGetBody(Callable c) { result = c.getBody() }
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/** A statement. Includes both wrapped `Stmt` nodes and `StmtList` blocks. */
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class Stmt extends AstNode {
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Stmt() { this instanceof Ast::StmtNode or this instanceof Ast::StmtListNode }
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}
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/** An expression. */
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class Expr extends Ast::ExprNode { }
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/** A block of statements, wrapping Python's `StmtList`. */
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class BlockStmt extends Stmt, Ast::StmtListNode {
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/** Gets the `n`th (zero-based) statement in this block. */
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Stmt getStmt(int n) { result = Ast::StmtListNode.super.getItem(n) }
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/** Gets the last statement in this block. */
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Stmt getLastStmt() { result = Ast::StmtListNode.super.getLastItem() }
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}
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/** An expression statement. */
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class ExprStmt extends Stmt, Ast::ExprStmtNode {
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/** Gets the expression in this expression statement. */
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Expr getExpr() { result = this.getValue() }
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}
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/**
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* An `if` statement.
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*
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* Python's `elif` chains are represented as nested `If` nodes in the
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* else branch's `StmtList`. The shared CFG library handles this naturally:
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* `getElse()` returns the `BlockStmt` wrapping the else branch, and if that
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* block contains a single `If`, the result is a chained conditional.
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*/
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class IfStmt extends Stmt, Ast::IfNode {
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/** Gets the condition of this `if` statement. */
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Expr getCondition() { result = this.getTest() }
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/** Gets the `then` (true) branch of this `if` statement. */
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Stmt getThen() { result = Ast::IfNode.super.getBody() }
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/** Gets the `else` (false) branch of this `if` statement, if any. */
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Stmt getElse() { result = this.getOrelse() }
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}
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// ===== Stub types for constructs not yet implemented =====
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/** A loop statement. Not yet implemented for Python. */
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class LoopStmt extends Stmt {
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LoopStmt() { none() }
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/** Gets the body of this loop statement. */
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Stmt getBody() { none() }
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}
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/** A `while` loop statement. Not yet implemented for Python. */
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class WhileStmt extends LoopStmt {
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/** Gets the boolean condition of this `while` loop. */
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Expr getCondition() { none() }
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}
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/** A `do-while` loop statement. Python has no do-while construct. */
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class DoStmt extends LoopStmt {
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/** Gets the boolean condition of this `do-while` loop. */
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Expr getCondition() { none() }
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}
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/** A C-style `for` loop. Python has no C-style for loop. */
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class ForStmt extends LoopStmt {
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/** Gets the initializer expression at the specified position. */
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Expr getInit(int index) { none() }
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/** Gets the boolean condition of this `for` loop. */
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Expr getCondition() { none() }
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/** Gets the update expression at the specified position. */
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Expr getUpdate(int index) { none() }
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}
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/** A for-each loop. Not yet implemented for Python. */
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class ForeachStmt extends LoopStmt {
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/** Gets the loop variable. */
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Expr getVariable() { none() }
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/** Gets the collection being iterated. */
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Expr getCollection() { none() }
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}
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/** A `break` statement. Not yet implemented for Python. */
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class BreakStmt extends Stmt {
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BreakStmt() { none() }
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}
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/** A `continue` statement. Not yet implemented for Python. */
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class ContinueStmt extends Stmt {
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ContinueStmt() { none() }
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}
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/** A `return` statement. Not yet implemented for Python. */
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class ReturnStmt extends Stmt {
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ReturnStmt() { none() }
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/** Gets the expression being returned, if any. */
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Expr getExpr() { none() }
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}
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/** A `throw`/`raise` statement. Not yet implemented for Python. */
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class ThrowStmt extends Stmt {
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ThrowStmt() { none() }
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/** Gets the expression being thrown. */
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Expr getExpr() { none() }
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}
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/** A `try` statement. Not yet implemented for Python. */
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class TryStmt extends Stmt {
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TryStmt() { none() }
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/** Gets the body of this `try` statement. */
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Stmt getBody() { none() }
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/** Gets the `catch` clause at the specified position. */
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CatchClause getCatch(int index) { none() }
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/** Gets the `finally` block of this `try` statement, if any. */
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Stmt getFinally() { none() }
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}
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/** A catch clause. Not yet implemented for Python. */
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class CatchClause extends AstNode {
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CatchClause() { none() }
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/** Gets the variable declared by this catch clause. */
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AstNode getVariable() { none() }
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/** Gets the guard condition, if any. */
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Expr getCondition() { none() }
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/** Gets the body of this catch clause. */
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Stmt getBody() { none() }
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}
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/** A switch/match statement. Not yet implemented for Python. */
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class Switch extends AstNode {
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Switch() { none() }
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/** Gets the expression being switched on. */
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Expr getExpr() { none() }
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/** Gets the case at the specified position. */
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Case getCase(int index) { none() }
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/** Gets the statement at the specified position. */
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Stmt getStmt(int index) { none() }
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}
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/** A case in a switch/match. Not yet implemented for Python. */
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class Case extends AstNode {
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Case() { none() }
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/** Gets a pattern being matched. */
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AstNode getAPattern() { none() }
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/** Gets the guard expression, if any. */
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Expr getGuard() { none() }
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/** Gets the body of this case. */
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AstNode getBody() { none() }
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}
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/** A default case. Not yet implemented for Python. */
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class DefaultCase extends Case { }
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/** A ternary conditional expression. Not yet implemented for Python. */
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class ConditionalExpr extends Expr {
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ConditionalExpr() { none() }
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/** Gets the condition of this expression. */
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Expr getCondition() { none() }
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/** Gets the true branch of this expression. */
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Expr getThen() { none() }
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/** Gets the false branch of this expression. */
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Expr getElse() { none() }
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}
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/** A binary expression. Not yet implemented for Python. */
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class BinaryExpr extends Expr {
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BinaryExpr() { none() }
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/** Gets the left operand. */
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Expr getLeftOperand() { none() }
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/** Gets the right operand. */
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Expr getRightOperand() { none() }
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}
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/** A short-circuiting logical AND expression. Not yet implemented for Python. */
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class LogicalAndExpr extends BinaryExpr { }
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/** A short-circuiting logical OR expression. Not yet implemented for Python. */
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class LogicalOrExpr extends BinaryExpr { }
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/** A null-coalescing expression. Python has no null-coalescing operator. */
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class NullCoalescingExpr extends BinaryExpr { }
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/** A unary expression. Not yet implemented for Python. */
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class UnaryExpr extends Expr {
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UnaryExpr() { none() }
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/** Gets the operand. */
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Expr getOperand() { none() }
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}
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/** A logical NOT expression. Not yet implemented for Python. */
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class LogicalNotExpr extends UnaryExpr { }
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/** A boolean literal expression. Not yet implemented for Python. */
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class BooleanLiteral extends Expr {
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BooleanLiteral() { none() }
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/** Gets the boolean value of this literal. */
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boolean getValue() { none() }
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}
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}
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