GH-392 Support effective lookup for return statement

panda-framework/src/main/java/org/panda_lang/framework/design/architecture/statement/Block.java

@@ -16,9 +16,11 @@
 
 package org.panda_lang.framework.design.architecture.statement;
 
+import org.panda_lang.framework.design.architecture.dynamic.Executable;
+
 /**
  * Represents block scopes
  */
-public interface Block extends Scope {
+public interface Block extends Scope, Executable {
 
 }

panda-framework/src/main/java/org/panda_lang/framework/design/architecture/statement/Scope.java

@@ -28,9 +28,17 @@ public interface Scope extends Statement {
      * Add given statement to the current scope
      *
      * @param statement the statement to add
-     * @return a cell where the statement was placed
+     * @return the statement
      */
-    Cell addStatement(Statement statement);
+    Statement addStatement(Statement statement);
+
+    /**
+     * Check if scope has effective (statement that is always reachable) statement of the given type
+     *
+     * @param statementClass type of statements to search for
+     * @return true if scope has effective statement of the given type, otherwise false
+     */
+    boolean hasEffective(Class<? extends Statement> statementClass);
 
     /**
      * Create variable with given properties in the current scope
@@ -71,11 +79,11 @@ public interface Scope extends Statement {
     List<? extends Variable> getVariables();
 
     /**
-     * Get all statements wrapped into cells
+     * Get all statements
      *
-     * @return list of all cells
+     * @return list of all statements
      */
-    List<? extends Cell> getCells();
+    List<? extends Statement> getStatements();
 
     /**
      * Get parent scope

panda/src/main/java/org/panda_lang/panda/language/resource/syntax/scope/block/conditional/ConditionalBlock.java

@@ -57,6 +57,14 @@ public ConditionalBlock(Scope parent, SourceLocation location, Expression condit
         return null;
     }
 
+    @Override
+    public boolean hasEffective(Class<? extends Statement> statementClass) {
+        boolean current = super.hasEffective(statementClass);
+        boolean otherwise = elseBlock == null || elseBlock.hasEffective(statementClass);
+
+        return current && otherwise;
+    }
+
     public void setElseBlock(Scope elseBlock) {
         this.elseBlock = elseBlock;
     }