Merge pull request #157 from github/cfg_impl

Port CFG implementation to public AST interface

Author: nickrolfe

ql/src/codeql_ruby/ast/Control.qll

@@ -440,6 +440,9 @@ class ConditionalLoop extends Loop, TConditionalLoop {
     or
     pred = "getCondition" and result = this.getCondition()
   }
+
+  /** Holds if the loop body is entered when the condition is `condValue`. */
+  predicate entersLoopWhenConditionIs(boolean condValue) { none() }
 }
 
 /**
@@ -463,6 +466,12 @@ class WhileExpr extends ConditionalLoop, TWhileExpr {
 
   final override Expr getCondition() { toGenerated(result) = g.getCondition() }
 
+  /**
+   * Holds if the loop body is entered when the condition is `condValue`. For
+   * `while` loops, this holds when `condValue` is true.
+   */
+  final override predicate entersLoopWhenConditionIs(boolean condValue) { condValue = true }
+
   final override string toString() { result = "while ..." }
 }
 
@@ -487,6 +496,12 @@ class UntilExpr extends ConditionalLoop, TUntilExpr {
 
   final override Expr getCondition() { toGenerated(result) = g.getCondition() }
 
+  /**
+   * Holds if the loop body is entered when the condition is `condValue`. For
+   * `until` loops, this holds when `condValue` is false.
+   */
+  final override predicate entersLoopWhenConditionIs(boolean condValue) { condValue = false }
+
   final override string toString() { result = "until ..." }
 }
 
@@ -505,6 +520,12 @@ class WhileModifierExpr extends ConditionalLoop, TWhileModifierExpr {
 
   final override Expr getCondition() { toGenerated(result) = g.getCondition() }
 
+  /**
+   * Holds if the loop body is entered when the condition is `condValue`. For
+   * `while`-modifier loops, this holds when `condValue` is true.
+   */
+  final override predicate entersLoopWhenConditionIs(boolean condValue) { condValue = true }
+
   final override string getAPrimaryQlClass() { result = "WhileModifierExpr" }
 
   final override string toString() { result = "... while ..." }
@@ -525,6 +546,12 @@ class UntilModifierExpr extends ConditionalLoop, TUntilModifierExpr {
 
   final override Expr getCondition() { toGenerated(result) = g.getCondition() }
 
+  /**
+   * Holds if the loop body is entered when the condition is `condValue`. For
+   * `until`-modifier loops, this holds when `condValue` is false.
+   */
+  final override predicate entersLoopWhenConditionIs(boolean condValue) { condValue = false }
+
   final override string getAPrimaryQlClass() { result = "UntilModifierExpr" }
 
   final override string toString() { result = "... until ..." }

ql/src/codeql_ruby/ast/Expr.qll

@@ -73,8 +73,8 @@ class StmtSequence extends Expr, TStmtSequence {
   /** Gets a statement in this sequence. */
   final Stmt getAStmt() { result = this.getStmt(_) }
 
-  /** Gets the last expression in this sequence, if any. */
-  final Expr getLastExpr() { result = this.getStmt(this.getNumberOfStatements() - 1) }
+  /** Gets the last statement in this sequence, if any. */
+  final Stmt getLastStmt() { result = this.getStmt(this.getNumberOfStatements() - 1) }
 
   /** Gets the number of statements in this sequence. */
   final int getNumberOfStatements() { result = count(this.getAStmt()) }

ql/src/codeql_ruby/ast/Method.qll

@@ -4,7 +4,7 @@ private import internal.AST
 private import internal.TreeSitter
 
 /** A callable. */
-class Callable extends Expr, CfgScope, TCallable {
+class Callable extends Expr, TCallable {
   /** Gets the number of parameters of this callable. */
   final int getNumberOfParameters() { result = count(this.getAParameter()) }
 

ql/src/codeql_ruby/ast/Module.qll

@@ -47,7 +47,8 @@ class Toplevel extends ModuleBase, TToplevel {
    * Gets the `n`th `BEGIN` block.
    */
   final BeginBlock getBeginBlock(int n) {
-    toGenerated(result) = rank[n](int i, Generated::BeginBlock b | b = g.getChild(i) | b order by i)
+    toGenerated(result) =
+      rank[n + 1](int i, Generated::BeginBlock b | b = g.getChild(i) | b order by i)
   }
 
   /**

ql/src/codeql_ruby/ast/Pattern.qll

@@ -63,7 +63,14 @@ class TuplePattern extends Pattern, TTuplePattern {
     or
     result = toGenerated(this).(Generated::DestructuredLeftAssignment).getChild(i)
     or
-    result = toGenerated(this).(Generated::LeftAssignmentList).getChild(i)
+    toGenerated(this) =
+      any(Generated::LeftAssignmentList lal |
+        if
+          strictcount(int j | exists(lal.getChild(j))) = 1 and
+          lal.getChild(0) instanceof Generated::DestructuredLeftAssignment
+        then result = lal.getChild(0).(Generated::DestructuredLeftAssignment).getChild(i)
+        else result = lal.getChild(i)
+      )
   }
 
   /** Gets the `i`th pattern in this tuple pattern. */

ql/src/codeql_ruby/ast/Statement.qll

@@ -15,7 +15,7 @@ class Stmt extends AstNode, TStmt {
   CfgNodes::AstCfgNode getAControlFlowNode() { result.getNode() = this }
 
   /** Gets the control-flow scope of this statement, if any. */
-  CfgScope getCfgScope() { result = getCfgScope(toGenerated(this)) }
+  CfgScope getCfgScope() { result = getCfgScope(this) }
 
   /** Gets the enclosing callable, if any. */
   Callable getEnclosingCallable() { result = this.getCfgScope() }

ql/src/codeql_ruby/ast/internal/AST.qll

@@ -90,7 +90,9 @@ private module Cached {
     TComplexLiteral(Generated::Complex g) or
     TDefinedExpr(Generated::Unary g) { g instanceof @unary_definedquestion } or
     TDelimitedSymbolLiteral(Generated::DelimitedSymbol g) or
-    TDestructuredLeftAssignment(Generated::DestructuredLeftAssignment g) or
+    TDestructuredLeftAssignment(Generated::DestructuredLeftAssignment g) {
+      not strictcount(int i | exists(g.getParent().(Generated::LeftAssignmentList).getChild(i))) = 1
+    } or
     TDivExpr(Generated::Binary g) { g instanceof @binary_slash } or
     TDo(Generated::Do g) or
     TDoBlock(Generated::DoBlock g) { not g.getParent() instanceof Generated::Lambda } or

ql/src/codeql_ruby/controlflow/CfgNodes.qll

@@ -1,7 +1,6 @@
 /** Provides classes representing nodes in a control flow graph. */
 
 private import codeql_ruby.AST
-private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.controlflow.BasicBlocks
 private import ControlFlowGraph
 private import internal.ControlFlowGraphImpl
@@ -67,7 +66,7 @@ class AstCfgNode extends CfgNode, TAstCfgNode {
   private Splits splits;
   private AstNode n;
 
-  AstCfgNode() { this = TAstCfgNode(toGenerated(n), splits) }
+  AstCfgNode() { this = TAstCfgNode(n, splits) }
 
   final override AstNode getNode() { result = n }
 
@@ -132,7 +131,7 @@ abstract private class ExprChildMapping extends Expr {
 
   pragma[noinline]
   private BasicBlock getABasicBlockInScope() {
-    result.getANode() = TAstCfgNode(toGenerated(this.getAChildStar()), _)
+    result.getANode() = TAstCfgNode(this.getAChildStar(), _)
   }
 
   pragma[nomagic]
@@ -284,7 +283,7 @@ module ExprNodes {
   }
 
   private class StmtSequenceChildMapping extends ExprChildMapping, StmtSequence {
-    override predicate relevantChild(Expr e) { e = this.getLastExpr() }
+    override predicate relevantChild(Expr e) { e = this.getLastStmt() }
   }
 
   /** A control-flow node that wraps a `StmtSequence` AST expression. */
@@ -293,8 +292,8 @@ module ExprNodes {
 
     final override StmtSequence getExpr() { result = ExprCfgNode.super.getExpr() }
 
-    /** Gets the last expression in this sequence, if any. */
-    final ExprCfgNode getLastExpr() { e.hasCfgChild(e.getLastExpr(), this, result) }
+    /** Gets the last statement in this sequence, if any. */
+    final ExprCfgNode getLastStmt() { e.hasCfgChild(e.getLastStmt(), this, result) }
   }
 
   private class ForExprChildMapping extends ExprChildMapping, ForExpr {

ql/src/codeql_ruby/controlflow/ControlFlowGraph.qll

@@ -1,23 +1,22 @@
 /** Provides classes representing the control flow graph. */
 
 private import codeql.Locations
-private import codeql_ruby.AST as AST
-private import codeql_ruby.ast.internal.AST as ASTInternal
+private import codeql_ruby.AST
 private import codeql_ruby.controlflow.BasicBlocks
 private import SuccessorTypes
 private import internal.ControlFlowGraphImpl
 private import internal.Splitting
 private import internal.Completion
 
 /** An AST node with an associated control-flow graph. */
-class CfgScope extends AST::AstNode {
-  CfgScope() { ASTInternal::toGenerated(this) instanceof CfgScope::Range_ }
+class CfgScope extends Scope {
+  CfgScope() { this instanceof CfgScope::Range_ }
 
   /** Gets the CFG scope that this scope is nested under, if any. */
   final CfgScope getOuterCfgScope() {
-    exists(AST::AstNode parent |
+    exists(AstNode parent |
       parent = this.getParent() and
-      result = getCfgScope(ASTInternal::toGenerated(parent))
+      result = getCfgScope(parent)
     )
   }
 }
@@ -35,7 +34,7 @@ class CfgNode extends TCfgNode {
   string toString() { none() }
 
   /** Gets the AST node that this node corresponds to, if any. */
-  AST::AstNode getNode() { none() }
+  AstNode getNode() { none() }
 
   /** Gets the location of this control flow node. */
   Location getLocation() { none() }