From aabdf8430075c4d1bc930799f0c68f4d3792c5ca Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Tue, 2 Aug 2022 14:29:03 +0200
Subject: [PATCH] Java: Improve join-order for `not haveIntersection`.

---
 java/ql/lib/semmle/code/java/Type.qll         | 23 +++++++++++++++++--
 .../Collections/ContainsTypeMismatch.ql       |  4 ++--
 .../Collections/RemoveTypeMismatch.ql         |  4 ++--
 .../Comparison/IncomparableEquals.ql          |  2 +-
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/java/ql/lib/semmle/code/java/Type.qll b/java/ql/lib/semmle/code/java/Type.qll
index 2e83c31f26a..256df5d66f3 100755
--- a/java/ql/lib/semmle/code/java/Type.qll
+++ b/java/ql/lib/semmle/code/java/Type.qll
@@ -1194,8 +1194,8 @@ private Type erase(Type t) {
 }
 
 /**
- * Is there a common (reflexive, transitive) subtype of the erasures of
- * types `t1` and `t2`?
+ * Holds if there is a common (reflexive, transitive) subtype of the erasures of
+ * types `t1` and `t2`.
  *
  * If there is no such common subtype, then the two types are disjoint.
  * However, the converse is not true; for example, the parameterized types
@@ -1212,6 +1212,25 @@ predicate haveIntersection(RefType t1, RefType t2) {
   )
 }
 
+/**
+ * Holds if there is no common (reflexive, transitive) subtype of the erasures
+ * of types `t1` and `t2`.
+ *
+ * If there is no such common subtype, then the two types are disjoint.
+ * However, the converse is not true; for example, the parameterized types
+ * `List<Integer>` and `Collection<String>` are disjoint,
+ * but their erasures (`List` and `Collection`, respectively)
+ * do have common subtypes (such as `List` itself).
+ *
+ * For the definition of the notion of *erasure* see JLS v8, section 4.6 (Type Erasure).
+ */
+bindingset[t1, t2]
+predicate notHaveIntersection(RefType t1, RefType t2) {
+  exists(RefType e1, RefType e2 | e1 = erase(t1) and e2 = erase(t2) |
+    not erasedHaveIntersection(e1, e2)
+  )
+}
+
 /**
  * Holds if there is a common (reflexive, transitive) subtype of the erased
  * types `t1` and `t2`.
diff --git a/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql b/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql
index b34830c3537..52d790e0e71 100644
--- a/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql	
+++ b/java/ql/src/Likely Bugs/Collections/ContainsTypeMismatch.ql	
@@ -118,7 +118,7 @@ class MismatchedContainerAccess extends MethodAccess {
       containerAccess(package, type, p, this.getCallee().getSignature(), i)
     |
       t = this.getCallee().getDeclaringType() and
-      t.getAnAncestor().getSourceDeclaration() = g and
+      t.getASourceSupertype*().getSourceDeclaration() = g and
       g.hasQualifiedName(package, type) and
       indirectlyInstantiates(t, g, p, result)
     )
@@ -139,7 +139,7 @@ from MismatchedContainerAccess ma, RefType typearg, RefType argtype, int idx
 where
   typearg = ma.getReceiverElementType(idx).getSourceDeclaration() and
   argtype = ma.getArgumentType(idx) and
-  not haveIntersection(typearg, argtype)
+  notHaveIntersection(typearg, argtype)
 select ma.getArgument(idx),
   "Actual argument type '" + argtype.getName() + "'" +
     " is incompatible with expected argument type '" + typearg.getName() + "'."
diff --git a/java/ql/src/Likely Bugs/Collections/RemoveTypeMismatch.ql b/java/ql/src/Likely Bugs/Collections/RemoveTypeMismatch.ql
index 8fa467c2d8a..076ccc12240 100644
--- a/java/ql/src/Likely Bugs/Collections/RemoveTypeMismatch.ql	
+++ b/java/ql/src/Likely Bugs/Collections/RemoveTypeMismatch.ql	
@@ -88,7 +88,7 @@ class MismatchedContainerModification extends MethodAccess {
       containerModification(package, type, p, this.getCallee().getSignature(), i)
     |
       t = this.getCallee().getDeclaringType() and
-      t.getAnAncestor().getSourceDeclaration() = g and
+      t.getASourceSupertype*().getSourceDeclaration() = g and
       g.hasQualifiedName(package, type) and
       indirectlyInstantiates(t, g, p, result)
     )
@@ -109,7 +109,7 @@ from MismatchedContainerModification ma, RefType elementtype, RefType argtype, i
 where
   elementtype = ma.getReceiverElementType(idx).getSourceDeclaration() and
   argtype = ma.getArgumentType(idx) and
-  not haveIntersection(elementtype, argtype)
+  notHaveIntersection(elementtype, argtype)
 select ma.getArgument(idx),
   "Actual argument type '" + argtype.getName() + "'" +
     " is incompatible with expected argument type '" + elementtype.getName() + "'."
diff --git a/java/ql/src/Likely Bugs/Comparison/IncomparableEquals.ql b/java/ql/src/Likely Bugs/Comparison/IncomparableEquals.ql
index c083c80c21d..d98fc77af38 100644
--- a/java/ql/src/Likely Bugs/Comparison/IncomparableEquals.ql	
+++ b/java/ql/src/Likely Bugs/Comparison/IncomparableEquals.ql	
@@ -57,7 +57,7 @@ where
     else recvtp = ma.getMethod().getDeclaringType()
   ) and
   argtp = ma.getArgumentType() and
-  not haveIntersection(recvtp, argtp)
+  notHaveIntersection(recvtp, argtp)
 select ma,
   "Call to equals() comparing incomparable types " + recvtp.getName() + " and " + argtp.getName() +
     "."