Introduce and use SwitchBlock instead of StmtParent for switch-statement-or-expression

Author: smowton

java/ql/lib/semmle/code/java/ControlFlowGraph.qll

@@ -440,7 +440,7 @@ private module ControlFlowGraphImpl {
   // Join order engineering -- first determine the switch block and the case indices required, then retrieve them.
   bindingset[switch, i]
   pragma[inline_late]
-  private predicate isNthCaseOf(StmtParent switch, SwitchCase c, int i) { c.isNthCaseOf(switch, i) }
+  private predicate isNthCaseOf(SwitchBlock switch, SwitchCase c, int i) { c.isNthCaseOf(switch, i) }
 
   /**
    * Gets a `SwitchCase` that may be `pred`'s direct successor, where `pred` is declared in block `switch`.
@@ -450,7 +450,7 @@ private module ControlFlowGraphImpl {
    * Because we know the switch block contains at least one pattern, we know by https://docs.oracle.com/javase/specs/jls/se21/html/jls-14.html#jls-14.11
    * that any default case comes after the last pattern case.
    */
-  private SwitchCase getASuccessorSwitchCase(PatternCase pred, StmtParent switch) {
+  private SwitchCase getASuccessorSwitchCase(PatternCase pred, SwitchBlock switch) {
     // Note we do include `case null, default` (as well as plain old `default`) here.
     not result.(ConstCase).getValue(_) instanceof NullLiteral and
     exists(int maxCaseIndex |
@@ -471,7 +471,7 @@ private module ControlFlowGraphImpl {
    *
    * Otherwise it is any case in the switch block.
    */
-  private SwitchCase getAFirstSwitchCase(StmtParent switch) {
+  private SwitchCase getAFirstSwitchCase(SwitchBlock switch) {
     result.getParent() = switch and
     (
       result.(ConstCase).getValue(_) instanceof NullLiteral
@@ -484,7 +484,7 @@ private module ControlFlowGraphImpl {
     )
   }
 
-  private Stmt getSwitchStatement(StmtParent switch, int i) { result.isNthChildOf(switch, i) }
+  private Stmt getSwitchStatement(SwitchBlock switch, int i) { result.isNthChildOf(switch, i) }
 
   /**
    * Holds if `last` is the last node in a pattern case `pc`'s succeeding bind-and-test operation,
@@ -1296,7 +1296,7 @@ private module ControlFlowGraphImpl {
     )
     or
     // Switch statements and expressions
-    exists(StmtParent switch | switch instanceof SwitchStmt or switch instanceof SwitchExpr |
+    exists(SwitchBlock switch |
       exists(Expr switchExpr |
         switchExpr = switch.(SwitchStmt).getExpr() or switchExpr = switch.(SwitchExpr).getExpr()
       |

java/ql/lib/semmle/code/java/Statement.qll

@@ -428,6 +428,13 @@ class SwitchStmt extends Stmt, @switchstmt {
   override string getAPrimaryQlClass() { result = "SwitchStmt" }
 }
 
+/**
+ * A `switch` statement or expression.
+ */
+class SwitchBlock extends StmtParent {
+  SwitchBlock() { this instanceof SwitchStmt or this instanceof SwitchExpr }
+}
+
 /**
  * A case of a `switch` statement or expression.
  *

java/ql/lib/semmle/code/java/controlflow/Guards.qll

@@ -76,13 +76,13 @@ class ConditionBlock extends BasicBlock {
 // Join order engineering -- first determine the switch block and the case indices required, then retrieve them.
 bindingset[switch, i]
 pragma[inline_late]
-private predicate isNthCaseOf(StmtParent switch, SwitchCase c, int i) { c.isNthCaseOf(switch, i) }
+private predicate isNthCaseOf(SwitchBlock switch, SwitchCase c, int i) { c.isNthCaseOf(switch, i) }
 
 /**
  * Gets a switch case >= pred, up to but not including `pred`'s successor pattern case,
  * where `pred` is declared on `switch`.
  */
-private SwitchCase getACaseUpToNextPattern(PatternCase pred, StmtParent switch) {
+private SwitchCase getACaseUpToNextPattern(PatternCase pred, SwitchBlock switch) {
   // Note we do include `case null, default` (as well as plain old `default`) here.
   not result.(ConstCase).getValue(_) instanceof NullLiteral and
   exists(int maxCaseIndex |

java/ql/lib/semmle/code/java/controlflow/internal/SwitchCases.qll

@@ -5,27 +5,27 @@ import java
 /**
  * Gets the `i`th `PatternCase` defined on `switch`, if one exists.
  */
-private PatternCase getPatternCase(StmtParent switch, int i) {
+private PatternCase getPatternCase(SwitchBlock switch, int i) {
   result =
     rank[i + 1](PatternCase pc, int caseIdx | pc.isNthCaseOf(switch, caseIdx) | pc order by caseIdx)
 }
 
 /**
  * Gets the first `PatternCase` defined on `switch`, if one exists.
  */
-PatternCase getFirstPatternCase(StmtParent switch) {
+PatternCase getFirstPatternCase(SwitchBlock switch) {
   result = getPatternCase(switch, 0)
 }
 
 /**
  * Gets the PatternCase after pc, if one exists.
  */
 PatternCase getNextPatternCase(PatternCase pc) {
-  exists(int idx, StmtParent switch |
+  exists(int idx, SwitchBlock switch |
     pc = getPatternCase(switch, idx) and result = getPatternCase(switch, idx + 1)
   )
 }
 
-int lastCaseIndex(StmtParent switch) {
+int lastCaseIndex(SwitchBlock switch) {
   result = max(int i | any(SwitchCase c).isNthCaseOf(switch, i))
 }