Ensure better Kotlin compatibility

In Kotlin the top-level LST element is a `K.CompilationUnit`, which isn't a subtype of `J.CompilationUnit`, but they both implement the `JavaSourceFile` interface.

src/main/java/org/openrewrite/analysis/dataflow/ExternalFlowModels.java

@@ -26,6 +26,7 @@
 import org.openrewrite.java.MethodMatcher;
 import org.openrewrite.java.internal.TypesInUse;
 import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaSourceFile;
 import org.openrewrite.java.tree.JavaType;
 
 import java.lang.ref.WeakReference;
@@ -68,10 +69,10 @@ private OptimizedFlowModels getOptimizedFlowModelsForTypesInUse(TypesInUse types
     }
 
     private OptimizedFlowModels getOrComputeOptimizedFlowModels(Cursor cursor) {
-        Cursor cuCursor = cursor.dropParentUntil(J.CompilationUnit.class::isInstance);
+        Cursor cuCursor = cursor.dropParentUntil(JavaSourceFile.class::isInstance);
         return cuCursor.computeMessageIfAbsent(
                 CURSOR_MESSAGE_KEY,
-                __ -> getOptimizedFlowModelsForTypesInUse(cuCursor.<J.CompilationUnit>getValue().getTypesInUse())
+                __ -> getOptimizedFlowModelsForTypesInUse(cuCursor.<JavaSourceFile>getValue().getTypesInUse())
         );
     }
 

src/main/java/org/openrewrite/analysis/dataflow/ExternalSinkModels.java

@@ -25,6 +25,7 @@
 import org.openrewrite.analysis.trait.expr.Call;
 import org.openrewrite.java.internal.TypesInUse;
 import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaSourceFile;
 import org.openrewrite.java.tree.JavaType;
 
 import java.lang.ref.WeakReference;
@@ -72,10 +73,10 @@ private OptimizedSinkModels getOptimizedSinkModelsForTypesInUse(TypesInUse types
     }
 
     private OptimizedSinkModels getOrComputeOptimizedSinkModels(Cursor cursor) {
-        Cursor cuCursor = cursor.dropParentUntil(J.CompilationUnit.class::isInstance);
+        Cursor cuCursor = cursor.dropParentUntil(JavaSourceFile.class::isInstance);
         return cuCursor.computeMessageIfAbsent(
                 CURSOR_MESSAGE_KEY,
-                __ -> getOptimizedSinkModelsForTypesInUse(cuCursor.<J.CompilationUnit>getValue().getTypesInUse())
+                __ -> getOptimizedSinkModelsForTypesInUse(cuCursor.<JavaSourceFile>getValue().getTypesInUse())
         );
     }
 

src/main/java/org/openrewrite/analysis/trait/expr/VarAccess.java

@@ -29,10 +29,7 @@
 import org.openrewrite.analysis.trait.variable.Variable;
 import org.openrewrite.analysis.trait.variable.VariableUtil;
 import org.openrewrite.java.JavaVisitor;
-import org.openrewrite.java.tree.Flag;
-import org.openrewrite.java.tree.J;
-import org.openrewrite.java.tree.JavaType;
-import org.openrewrite.java.tree.Javadoc;
+import org.openrewrite.java.tree.*;
 
 import java.util.ArrayList;
 import java.util.Collection;
@@ -172,7 +169,7 @@ public boolean isRValue() {
     }
 
     private static Variable computeVariable(VarAccessBase varAccess, Cursor cursor, J.Identifier varAccessIdent) {
-        Cursor compilationUnit = cursor.dropParentUntil(J.CompilationUnit.class::isInstance);
+        Cursor compilationUnit = cursor.dropParentUntil(JavaSourceFile.class::isInstance);
         AtomicBoolean found = new AtomicBoolean(false);
         Variable[] closestVariable = new Variable[1];
         new JavaVisitor<AtomicBoolean>() {
@@ -357,7 +354,7 @@ public Collection<Flag> getFlags() {
     }
 
     static Field create(JavaType.Variable variable, Cursor anyCursor) {
-        return new FieldFromJavaTypeVariable(variable, anyCursor.dropParentUntil(J.CompilationUnit.class::isInstance));
+        return new FieldFromJavaTypeVariable(variable, anyCursor.dropParentUntil(JavaSourceFile.class::isInstance));
     }
 }
 

src/main/java/org/openrewrite/analysis/trait/variable/Field.java

@@ -29,6 +29,7 @@
 import org.openrewrite.analysis.util.FlagUtil;
 import org.openrewrite.java.tree.Flag;
 import org.openrewrite.java.tree.J;
+import org.openrewrite.java.tree.JavaSourceFile;
 import org.openrewrite.java.tree.JavaType;
 
 import java.util.Collection;
@@ -99,13 +100,13 @@ public Option<JavaType> getType() {
     public Collection<VarAccess> getVarAccesses() {
         // Searching starts at the J.CompilationUnit because we want to find all references to this field, within the file,
         // not just within the class (which may contain multiple classes).
-        Cursor searchScope = parentBlock.dropParentUntil(J.CompilationUnit.class::isInstance);
+        Cursor searchScope = parentBlock.dropParentUntil(JavaSourceFile.class::isInstance);
         return VarAccess.findAllInScope(searchScope, this);
     }
 
     @Override
     public Collection<Expr> getAssignedValues() {
-        return VariableUtil.findAssignedValues(parentBlock.dropParentUntil(J.CompilationUnit.class::isInstance), this);
+        return VariableUtil.findAssignedValues(parentBlock.dropParentUntil(JavaSourceFile.class::isInstance), this);
     }
 
     @Override

src/main/java/org/openrewrite/analysis/trait/variable/LocalVariableDecl.java

@@ -31,10 +31,7 @@
 import org.openrewrite.analysis.trait.member.StaticInitializerMethod;
 import org.openrewrite.analysis.trait.util.TraitErrors;
 import org.openrewrite.analysis.util.FlagUtil;
-import org.openrewrite.java.tree.Flag;
-import org.openrewrite.java.tree.J;
-import org.openrewrite.java.tree.JavaType;
-import org.openrewrite.java.tree.Statement;
+import org.openrewrite.java.tree.*;
 
 import java.util.Collection;
 import java.util.Iterator;
@@ -89,12 +86,12 @@ public Option<JavaType> getType() {
 
     @Override
     public Collection<VarAccess> getVarAccesses() {
-        return VarAccess.findAllInScope(cursor.dropParentUntil(J.CompilationUnit.class::isInstance), this);
+        return VarAccess.findAllInScope(cursor.dropParentUntil(JavaSourceFile.class::isInstance), this);
     }
 
     @Override
     public Collection<Expr> getAssignedValues() {
-        return VariableUtil.findAssignedValues(cursor.dropParentUntil(J.CompilationUnit.class::isInstance), this);
+        return VariableUtil.findAssignedValues(cursor.dropParentUntil(JavaSourceFile.class::isInstance), this);
     }
 
     @Override