QL4QL: Add overlay[discard_entity] annotation

Author: kaspersv

ql/ql/src/codeql_ql/ast/Ast.qll

@@ -2554,6 +2554,10 @@ private class LocalQArg extends AnnotationArg {
   LocalQArg() { this.getValue() = "local?" }
 }
 
+private class DiscardEntityArg extends AnnotationArg {
+  DiscardEntityArg() { this.getValue() = "discard_entity" }
+}
+
 private class MonotonicAggregatesArg extends AnnotationArg {
   MonotonicAggregatesArg() { this.getValue() = "monotonicAggregates" }
 }
@@ -2641,6 +2645,13 @@ class OverlayLocalQ extends Annotation {
   override string toString() { result = "overlay[local?]" }
 }
 
+/** An `overlay[discard_entity]` annotation. */
+class OverlayDiscardEntity extends Annotation {
+  OverlayDiscardEntity() { this.getName() = "overlay" and this.getArgs(0) instanceof DiscardEntityArg }
+
+  override string toString() { result = "overlay[discard_entity]" }
+}
+
 /** A `language[monotonicAggregates]` annotation. */
 class MonotonicAggregates extends Annotation {
   MonotonicAggregates() { this.getArgs(0) instanceof MonotonicAggregatesArg }