diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/GroovyPsiElementFactory.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/GroovyPsiElementFactory.java
index 6b585f1f8f10..76a29cac4bf7 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/GroovyPsiElementFactory.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/GroovyPsiElementFactory.java
@@ -110,7 +110,7 @@ public abstract class GroovyPsiElementFactory {
   public abstract GrVariableDeclaration createFieldDeclaration(String[] modifiers, String identifier, GrExpression initializer, PsiType type);
   public abstract GrVariableDeclaration createFieldDeclarationFromText(String text);
 
-  public abstract GrVariableDeclaration createVariableDeclaration(String[] modifiers, @Nullable GrExpression initializer, PsiType type, String... identifiers);
+  public abstract GrVariableDeclaration createVariableDeclaration(@Nullable String[] modifiers, @Nullable GrExpression initializer, PsiType type, String... identifiers);
 
   public abstract GrEnumConstant createEnumConstantFromText(String text);
 
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/api/statements/blocks/GrClosableBlock.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/api/statements/blocks/GrClosableBlock.java
index b2e7dc6a1c0c..4038bfc725e3 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/api/statements/blocks/GrClosableBlock.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/api/statements/blocks/GrClosableBlock.java
@@ -18,6 +18,7 @@ package org.jetbrains.plugins.groovy.lang.psi.api.statements.blocks;
 
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiType;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.GrParametersOwner;
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrExpression;
@@ -33,6 +34,7 @@ public interface GrClosableBlock extends GrExpression, GrCodeBlock, GrParameters
   String OWNER_NAME = "owner";
   String IT_PARAMETER_NAME = "it";
 
+  @NotNull
   GrParameterList getParameterList();
 
   void addParameter(GrParameter parameter);
diff --git a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/blocks/GrClosableBlockImpl.java b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/blocks/GrClosableBlockImpl.java
index b7226da10d49..4889163acc71 100644
--- a/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/blocks/GrClosableBlockImpl.java
+++ b/plugins/groovy/src/org/jetbrains/plugins/groovy/lang/psi/impl/statements/blocks/GrClosableBlockImpl.java
@@ -23,6 +23,7 @@ import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.Function;
 import com.intellij.util.IncorrectOperationException;
+import com.intellij.util.NullableFunction;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.plugins.groovy.lang.lexer.GroovyTokenTypes;
@@ -118,10 +119,7 @@ public class GrClosableBlockImpl extends GrBlockImpl implements GrClosableBlock
   public GrParameter[] getParameters() {
     if (hasParametersSection()) {
       GrParameterListImpl parameterList = getParameterList();
-      if (parameterList != null) {
-        return parameterList.getParameters();
-      }
-
+      return parameterList.getParameters();
     }
 
     return GrParameter.EMPTY_ARRAY;
@@ -138,8 +136,12 @@ public class GrClosableBlockImpl extends GrBlockImpl implements GrClosableBlock
     return findPsiChildByType(GroovyTokenTypes.mCLOSABLE_BLOCK_OP);
   }
 
+
+  @NotNull
   public GrParameterListImpl getParameterList() {
-    return findChildByClass(GrParameterListImpl.class);
+    final GrParameterListImpl childByClass = findChildByClass(GrParameterListImpl.class);
+    assert childByClass != null;
+    return childByClass;
   }
 
   public void addParameter(GrParameter parameter) {
@@ -212,7 +214,7 @@ public class GrClosableBlockImpl extends GrBlockImpl implements GrClosableBlock
     return PsiImplUtil.replaceExpression(this, newExpr, removeUnnecessaryParentheses);
   }
 
-  private static final Function<GrClosableBlock, PsiType> ourTypesCalculator = new Function<GrClosableBlock, PsiType>() {
+  private static final Function<GrClosableBlock, PsiType> ourTypesCalculator = new NullableFunction<GrClosableBlock, PsiType>() {
     public PsiType fun(GrClosableBlock block) {
       return GroovyPsiManager.inferType(block, new MethodTypeInferencer(block));
     }