Distinguish record patterns that do or don't declare identifiers

Author: smowton

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

@@ -2739,4 +2739,14 @@ class RecordPatternExpr extends Expr, @recordpatternexpr {
       )
     )
   }
+
+  /**
+   * Holds if this record pattern declares any identifiers (i.e., at least one leaf declaration is named).
+   */
+  predicate declaresAnyIdentifiers() {
+    exists(PatternExpr subPattern | subPattern = this.getSubPattern(_) |
+      subPattern.asRecordPattern().declaresAnyIdentifiers() or
+      not subPattern.asBindingOrUnnamedPattern().isAnonymous()
+    )
+  }
 }

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowUtil.qll

@@ -194,14 +194,17 @@ predicate simpleAstFlowStep(Expr e1, Expr e2) {
   // In the following three cases only record patterns need this flow edge, leading from the bound instanceof
   // or switch tested expression to a record pattern that will read its fields. Simple binding patterns are
   // handled via VariableAssign.getSource instead.
-  // We only consider unique patterns because cases that declare multiple patterns are not allowed to declare
-  // any identifiers, so can't participate in dataflow.
-  exists(SwitchExpr se |
-    e1 = se.getExpr() and e2 = se.getACase().(PatternCase).getUniquePattern().asRecordPattern()
+  // We only consider patterns that declare any identifiers
+  exists(SwitchExpr se, RecordPatternExpr recordPattern | recordPattern = e2 |
+    e1 = se.getExpr() and
+    recordPattern = se.getACase().(PatternCase).getAPattern() and
+    recordPattern.declaresAnyIdentifiers()
   )
   or
-  exists(SwitchStmt ss |
-    e1 = ss.getExpr() and e2 = ss.getACase().(PatternCase).getUniquePattern().asRecordPattern()
+  exists(SwitchStmt ss, RecordPatternExpr recordPattern | recordPattern = e2 |
+    e1 = ss.getExpr() and
+    recordPattern = ss.getACase().(PatternCase).getAPattern() and
+    recordPattern.declaresAnyIdentifiers()
   )
   or
   exists(InstanceOfExpr ioe | e1 = ioe.getExpr() and e2 = ioe.getPattern().asRecordPattern())