Define entity discard predicates for Java

Author: kaspersv

java/ql/lib/java.qll

@@ -26,6 +26,7 @@ import semmle.code.java.KotlinType
 import semmle.code.java.Member
 import semmle.code.java.Modifier
 import semmle.code.java.Modules
+import semmle.code.java.Overlay
 import semmle.code.java.Package
 import semmle.code.java.Statement
 import semmle.code.java.Type

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

@@ -221,3 +221,17 @@ private predicate fixedHasLocation(Top l, Location loc, File f) {
   not hasSourceLocation(l, _, _) and
   locations_default(loc, f, _, _, _, _)
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableLocation(string file, @location l) {
+  not hasOverlay() and
+  file = getRawFileForLoc(l) and
+  not exists(@file f | hasLocation(f, l))
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardLocation(@location l) {
+  exists(string file | discardableLocation(file, l) and discardFile(file))
+}

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

@@ -2701,3 +2701,16 @@ class RecordPatternExpr extends Expr, @recordpatternexpr {
     )
   }
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableExpr(string file, @expr e) {
+  not hasOverlay() and
+  file = getRawFile(e)
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardExpr(@expr e) {
+  exists(string file | discardableExpr(file, e) and discardFile(file))
+}

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

@@ -196,3 +196,16 @@ class KtCommentSection extends @ktcommentsection {
   /** Gets the string representation of this section. */
   string toString() { result = this.getContent() }
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableJavadoc(string file, @javadoc d) {
+  not hasOverlay() and
+  exists(@member m | file = getRawFile(m) and hasJavadoc(m, d))
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardJavadoc(@javadoc d) {
+  exists(string file | discardableJavadoc(file, d) and discardFile(file))
+}

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

@@ -897,3 +897,36 @@ class ExtensionMethod extends Method {
     else result = 0
   }
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableMethod(string file, @method m) {
+  not hasOverlay() and
+  file = getRawFile(m) and
+  exists(@classorinterface c | methods(m, _, _, _, c, _) and isAnonymClass(c, _))
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardAnonMethod(@method m) {
+  exists(string file | discardableMethod(file, m) and discardFile(file))
+}
+
+overlay[local]
+pragma[nomagic]
+predicate discardableBaseMethod(string file, @method m) {
+  not hasOverlay() and
+  file = getRawFile(m)
+}
+
+overlay[local]
+pragma[nomagic]
+predicate usedOverlayMethod(@method m) { hasOverlay() and methods(m, _, _, _, _, _) }
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardMethod(@method m) {
+  exists(string file |
+    discardableBaseMethod(file, m) and discardFile(file) and not usedOverlayMethod(m)
+  )
+}

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

@@ -0,0 +1,29 @@
+overlay[local?]
+module;
+
+import java
+
+overlay[local]
+pragma[nomagic]
+predicate hasOverlay() { databaseMetadata("isOverlay", "true") }
+
+overlay[local]
+string getRawFile(@locatable el) {
+  exists(@location loc, @file file |
+    hasLocation(el, loc) and
+    locations_default(loc, file, _, _, _, _) and
+    files(file, result)
+  )
+}
+
+overlay[local]
+string getRawFileForLoc(@location l) {
+  exists(@file f | locations_default(l, f, _, _, _, _) and files(f, result))
+}
+
+overlay[local]
+pragma[nomagic]
+predicate discardFile(string file) {
+  hasOverlay() and
+  exists(@expr e | callableEnclosingExpr(e, _) and file = getRawFile(e))
+}

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

@@ -987,3 +987,16 @@ class SuperConstructorInvocationStmt extends Stmt, ConstructorCall, @superconstr
 
   override string getAPrimaryQlClass() { result = "SuperConstructorInvocationStmt" }
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableStmt(string file, @stmt s) {
+  not hasOverlay() and
+  file = getRawFile(s)
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardStmt(@stmt s) {
+  exists(string file | discardableStmt(file, s) and discardFile(file))
+}

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

@@ -133,3 +133,16 @@ class Parameter extends Element, @param, LocalScopeVariable {
   /** Holds if this is an anonymous parameter, `_` */
   predicate isAnonymous() { this.getName() = "" }
 }
+
+overlay[local]
+pragma[nomagic]
+predicate discardableLocalVarDecl(string file, @localscopevariable l) {
+  not hasOverlay() and
+  file = getRawFile(l)
+}
+
+overlay[discard_entity]
+pragma[nomagic]
+predicate discardLocalVarDecl(@localscopevariable l) {
+  exists(string file | discardableLocalVarDecl(file, l) and discardFile(file))
+}