diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ClosureConstraint.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ClosureConstraint.kt
index 6fcc58b78897..aabdcf5c67be 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ClosureConstraint.kt
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ClosureConstraint.kt
@@ -2,10 +2,8 @@
 package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
 
 import com.intellij.psi.PsiClassType
-import com.intellij.psi.PsiSubstitutor
 import com.intellij.psi.PsiType
 import com.intellij.psi.impl.source.resolve.graphInference.FunctionalInterfaceParameterizationUtil.getNonWildcardParameterization
-import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.blocks.GrClosableBlock
 import org.jetbrains.plugins.groovy.lang.psi.impl.signatures.GrClosureSignatureUtil.findCall
@@ -14,10 +12,10 @@ import org.jetbrains.plugins.groovy.lang.psi.util.GroovyCommonClassNames
 import org.jetbrains.plugins.groovy.lang.sam.findSingleAbstractMethod
 import org.jetbrains.plugins.groovy.lang.sam.isSamConversionAllowed
 
-class ClosureConstraint(private val closure: GrClosableBlock, private val leftType: PsiType) : ConstraintFormula {
+class ClosureConstraint(private val closure: GrClosableBlock, private val leftType: PsiType) : GrConstraintFormula() {
 
-  override fun reduce(session: InferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
-    if ((session as GroovyInferenceSession).skipClosureBlock || session.closureSkipList.contains(findCall(closure))) {
+  override fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
+    if (session.skipClosureBlock || session.closureSkipList.contains(findCall(closure))) {
       //TODO:add explicit typed closure constraints
     }
     else {
@@ -57,6 +55,4 @@ class ClosureConstraint(private val closure: GrClosableBlock, private val leftTy
     }
     return null
   }
-
-  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) {}
 }
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ExpressionConstraint.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ExpressionConstraint.kt
index 521f2c9e102d..c7891aeb17cb 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ExpressionConstraint.kt
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ExpressionConstraint.kt
@@ -1,18 +1,16 @@
 // Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
 
-import com.intellij.psi.PsiSubstitutor
 import com.intellij.psi.PsiType
-import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.blocks.GrClosableBlock
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrExpression
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrMethodCall
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrReferenceExpression
 
-class ExpressionConstraint(private val expression: GrExpression, private val leftType: PsiType?) : ConstraintFormula {
+class ExpressionConstraint(private val expression: GrExpression, private val leftType: PsiType?) : GrConstraintFormula() {
 
-  override fun reduce(session: InferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
+  override fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
     when (expression) {
       is GrMethodCall -> {
         val invokedExpression = expression.invokedExpression as? GrReferenceExpression ?: return true
@@ -23,6 +21,4 @@ class ExpressionConstraint(private val expression: GrExpression, private val lef
     }
     return true
   }
-
-  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) {}
 }
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/GrConstraintFormula.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/GrConstraintFormula.kt
new file mode 100644
index 000000000000..74a85d0322d9
--- /dev/null
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/GrConstraintFormula.kt
@@ -0,0 +1,18 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
+
+import com.intellij.psi.PsiSubstitutor
+import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
+import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
+
+abstract class GrConstraintFormula : ConstraintFormula {
+
+  final override fun reduce(session: InferenceSession?, constraints: MutableList<ConstraintFormula>): Boolean {
+    if (session !is GroovyInferenceSession) return true
+    return reduce(session, constraints)
+  }
+
+  abstract fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean
+
+  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) = Unit
+}
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/MethodCallConstraint.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/MethodCallConstraint.kt
index 6814b1088897..268d2cee25f8 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/MethodCallConstraint.kt
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/MethodCallConstraint.kt
@@ -1,14 +1,12 @@
 // Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
 
-import com.intellij.psi.PsiSubstitutor
-import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrReferenceExpression
 
-class MethodCallConstraint(private val callRef: GrReferenceExpression, private val candidate: MethodCandidate) : ConstraintFormula {
+class MethodCallConstraint(private val callRef: GrReferenceExpression, private val candidate: MethodCandidate) : GrConstraintFormula() {
 
-  override fun reduce(session: InferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
+  override fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
     processArguments(constraints)
     return true
   }
@@ -27,6 +25,4 @@ class MethodCallConstraint(private val callRef: GrReferenceExpression, private v
       }
     }
   }
-
-  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) {}
-}
\ No newline at end of file
+}
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ReferenceExpressionConstraint.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ReferenceExpressionConstraint.kt
index e3ab2b47bde4..d9acb4b1fa8f 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ReferenceExpressionConstraint.kt
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/ReferenceExpressionConstraint.kt
@@ -1,19 +1,16 @@
 // Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
 
-import com.intellij.psi.PsiSubstitutor
 import com.intellij.psi.PsiType
-import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.TypeCompatibilityConstraint
 import org.jetbrains.plugins.groovy.lang.psi.api.GroovyMethodResult
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrReferenceExpression
 import org.jetbrains.plugins.groovy.lang.psi.util.PsiUtil
 
-class ReferenceExpressionConstraint(private val callRef: GrReferenceExpression, private val leftType: PsiType?) : ConstraintFormula {
+class ReferenceExpressionConstraint(private val callRef: GrReferenceExpression, private val leftType: PsiType?) : GrConstraintFormula() {
 
-  override fun reduce(session: InferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
-    if (session !is GroovyInferenceSession) return true
+  override fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
     val resolved = callRef.advancedResolve()
     if (resolved !is GroovyMethodResult) return true
     resolved.candidate?.let {
@@ -44,6 +41,4 @@ class ReferenceExpressionConstraint(private val callRef: GrReferenceExpression,
     }
     return true
   }
-
-  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) {}
 }
diff --git a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/TypeConstraint.kt b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/TypeConstraint.kt
index 7bb2108a0950..3ba8c176b8c9 100644
--- a/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/TypeConstraint.kt
+++ b/plugins/groovy/groovy-psi/src/org/jetbrains/plugins/groovy/lang/resolve/processors/inference/TypeConstraint.kt
@@ -3,9 +3,7 @@ package org.jetbrains.plugins.groovy.lang.resolve.processors.inference
 
 import com.intellij.psi.CommonClassNames
 import com.intellij.psi.PsiElement
-import com.intellij.psi.PsiSubstitutor
 import com.intellij.psi.PsiType
-import com.intellij.psi.impl.source.resolve.graphInference.InferenceSession
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.ConstraintFormula
 import com.intellij.psi.impl.source.resolve.graphInference.constraints.TypeCompatibilityConstraint
 import org.jetbrains.plugins.groovy.lang.psi.impl.GrLiteralClassType
@@ -13,10 +11,9 @@ import org.jetbrains.plugins.groovy.lang.psi.impl.GrMapType
 import org.jetbrains.plugins.groovy.lang.psi.impl.GrTupleType
 import org.jetbrains.plugins.groovy.lang.psi.impl.statements.expressions.TypesUtil
 
-class TypeConstraint(private val leftType: PsiType, private val rightType: PsiType?, private val context: PsiElement) : ConstraintFormula {
+class TypeConstraint(private val leftType: PsiType, private val rightType: PsiType?, private val context: PsiElement) : GrConstraintFormula() {
 
-  override fun reduce(session: InferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
-    if (session !is GroovyInferenceSession) return true
+  override fun reduce(session: GroovyInferenceSession, constraints: MutableList<ConstraintFormula>): Boolean {
     var argType = rightType ?: PsiType.NULL
     if (argType is GrTupleType) {
       val rawWildcardType = TypesUtil.rawWildcard(argType, context)
@@ -34,6 +31,4 @@ class TypeConstraint(private val leftType: PsiType, private val rightType: PsiTy
     constraints.add(TypeCompatibilityConstraint(t, s))
     return true
   }
-
-  override fun apply(substitutor: PsiSubstitutor, cache: Boolean) {}
 }