Merge pull request github#17970 from owen-mc/java/lightweight-IR-layer

Java: IPA the CFG (second try)

Author: owen-mc

java/ql/consistency-queries/cfgDeadEnds.ql

@@ -1,7 +1,6 @@
 import java
-import semmle.code.java.ControlFlowGraph
 
-predicate shouldBeDeadEnd(ControlFlowNode n) {
+predicate shouldBeDeadEnd(ExprParent n) {
   n instanceof BreakStmt and n.getFile().isKotlinSourceFile() // TODO
   or
   n instanceof Interface // TODO
@@ -55,8 +54,11 @@ predicate shouldBeDeadEnd(ControlFlowNode n) {
   n = any(ConstCase c).getValue(_) // TODO
 }
 
-from ControlFlowNode n, string s
+from ControlFlowNode n, ExprParent astnode, string s
 where
-  // TODO: exists(n.getASuccessor()) and shouldBeDeadEnd(n) and s = "expected dead end"
-  not exists(n.getASuccessor()) and not shouldBeDeadEnd(n) and s = "unexpected dead end"
-select n, n.getPrimaryQlClasses(), s
+  astnode = n.getAstNode() and
+  // TODO: exists(n.getASuccessor()) and shouldBeDeadEnd(n.getAstNode()) and s = "expected dead end"
+  not exists(n.getASuccessor()) and
+  not shouldBeDeadEnd(astnode) and
+  s = "unexpected dead end"
+select n, astnode.getPrimaryQlClasses(), s

java/ql/lib/change-notes/2024-11-14-control-flow-graph-lightweight-IR-layer.md

@@ -0,0 +1,13 @@
+---
+category: breaking
+---
+* The class `ControlFlowNode` (and by extension `BasicBlock`) is no longer
+  directly equatable to `Expr` and `Stmt`. Any queries that have been
+  exploiting these equalities, for example by using casts, will need minor
+  updates in order to fix any compilation errors. Conversions can be inserted
+  in either direction depending on what is most convenient. Available
+  conversions include `Expr.getControlFlowNode()`, `Stmt.getControlFlowNode()`,
+  `ControlFlowNode.asExpr()`, `ControlFlowNode.asStmt()`, and
+  `ControlFlowNode.asCall()`. Exit nodes were until now modelled as a
+  `ControlFlowNode` equal to its enclosing `Callable`; these are now instead
+  modelled by the class `ControlFlow::ExitNode`.