From 7a707aa7b62ec51ae2cbbcbc674e9c683be9a04b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bendeg=C3=BAz=20Nagy?= <bendeguz.nagy.rf@gmail.com>
Date: Sun, 6 Aug 2017 22:41:29 +0200
Subject: [PATCH] Java, typeres: add erased candidate set and minimal erased
 candidate set methods

---
 .../typeresolution/MethodTypeResolution.java  |  4 +++
 .../typeinference/TypeInferenceResolver.java  | 33 +++++++++++++++++++
 .../pmd/typeresolution/TypeInferenceTest.java | 27 ++++++++++++++-
 3 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/MethodTypeResolution.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/MethodTypeResolution.java
index 9fb3c15305..e0750db818 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/MethodTypeResolution.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/MethodTypeResolution.java
@@ -484,6 +484,10 @@ public final class MethodTypeResolution {
         return isSubtypeable(parameter, argument.getTypeDefinition());
     }
 
+    public static boolean isSubtypeable(Class<?> parameter, Class<?> argument) {
+        return isSubtypeable(JavaTypeDefinition.forClass(parameter), JavaTypeDefinition.forClass(argument));
+    }
+
     /**
      * Subtypeability rules.
      * https://docs.oracle.com/javase/specs/jls/se7/html/jls-4.html#jls-4.10
diff --git a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/typeinference/TypeInferenceResolver.java b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/typeinference/TypeInferenceResolver.java
index b4deb26c1b..1f38a90673 100644
--- a/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/typeinference/TypeInferenceResolver.java
+++ b/pmd-java/src/main/java/net/sourceforge/pmd/lang/java/typeresolution/typeinference/TypeInferenceResolver.java
@@ -4,6 +4,7 @@
 
 package net.sourceforge.pmd.lang.java.typeresolution.typeinference;
 
+import net.sourceforge.pmd.lang.java.typeresolution.MethodTypeResolution;
 import net.sourceforge.pmd.lang.java.typeresolution.typedefinition.JavaTypeDefinition;
 
 import static net.sourceforge.pmd.lang.java.typeresolution.typeinference.InferenceRuleType.EQUALITY;
@@ -26,6 +27,38 @@ public final class TypeInferenceResolver {
 
     }
 
+    public static Set<Class<?>> getErasedCandidateSet(List<Set<Class<?>>> erasedSuperTypeSets) {
+        Set<Class<?>> result = new HashSet<>();
+
+        if (!erasedSuperTypeSets.isEmpty()) {
+            result.addAll(erasedSuperTypeSets.get(0));
+        }
+
+        for (Set<Class<?>> superTypeSet : erasedSuperTypeSets) {
+            result.retainAll(superTypeSet);
+        }
+
+        return result;
+    }
+
+    public static Set<Class<?>> getMinimalErasedCandidateSet(Set<Class<?>> erasedSet) {
+        Set<Class<?>> result = new HashSet<>();
+
+        outter:
+        for (Class<?> candidate : erasedSet) {
+            for (Class<?> erasedSetMember : erasedSet) {
+                if (candidate != erasedSetMember
+                        && MethodTypeResolution.isSubtypeable(candidate, erasedSetMember)) {
+                    continue outter; // skip candidate from result set
+                }
+            }
+
+            result.add(candidate);
+        }
+
+        return result;
+    }
+
     /**
      * Resolve unresolved variables in a list of bounds.
      */
diff --git a/pmd-java/src/test/java/net/sourceforge/pmd/typeresolution/TypeInferenceTest.java b/pmd-java/src/test/java/net/sourceforge/pmd/typeresolution/TypeInferenceTest.java
index ed31b98676..0bcd6e314a 100644
--- a/pmd-java/src/test/java/net/sourceforge/pmd/typeresolution/TypeInferenceTest.java
+++ b/pmd-java/src/test/java/net/sourceforge/pmd/typeresolution/TypeInferenceTest.java
@@ -12,8 +12,10 @@ import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import org.junit.Test;
 
@@ -278,7 +280,7 @@ public class TypeInferenceTest {
     @Test
     public void testIncorporationSubtypeAndSubtype() {
         List<Constraint> result;
-        
+
         // ### Original rule 4. : S <: α and α <: T imply ‹S <: T›
         result = incorporationResult(new Bound(s, alpha, EQUALITY), new Bound(alpha, t, SUBTYPE));
         assertEquals(result.size(), 1);
@@ -291,6 +293,29 @@ public class TypeInferenceTest {
 
     }
 
+    @Test
+    public void testErasedCandidateSet() {
+        List<Set<Class<?>>> superTypeSets = new ArrayList<>();
+        superTypeSets.add(JavaTypeDefinition.forClass(List.class).getErasedSuperTypeSet());
+        superTypeSets.add(JavaTypeDefinition.forClass(Set.class).getErasedSuperTypeSet());
+
+        Set<Class<?>> erasedCandidate = TypeInferenceResolver.getErasedCandidateSet(superTypeSets);
+
+        assertEquals(erasedCandidate.size(), 3);
+        assertTrue(erasedCandidate.contains(Object.class));
+        assertTrue(erasedCandidate.contains(Collection.class));
+        assertTrue(erasedCandidate.contains(Iterable.class));
+    }
+
+    @Test
+    public void testMinimalErasedCandidateSet() {
+        Set<Class<?>> minimalSet = TypeInferenceResolver.getMinimalErasedCandidateSet(
+                JavaTypeDefinition.forClass(List.class).getErasedSuperTypeSet());
+
+        assertEquals(minimalSet.size(), 1);
+        assertTrue(minimalSet.contains(List.class));
+    }
+
     private List<Constraint> incorporationResult(Bound firstBound, Bound secondBound) {
         List<Bound> current = new ArrayList<>();
         List<Bound> newBounds = new ArrayList<>();