diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
index fbd04e531e22..688aec9625af 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
@@ -115,4 +115,9 @@ public abstract class InputOutputConstraintFormula implements ConstraintFormula
     }
     map.put(getExpression(), getT());
   }
+
+  @Override
+  public String toString() {
+    return "T: " + getT().getCanonicalText() + "; expr : " + getExpression().getText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
index 12e7bfe9756b..20063af77749 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/LambdaExpressionCompatibilityConstraint.java
@@ -77,4 +77,9 @@ public class LambdaExpressionCompatibilityConstraint implements ConstraintFormul
   public void apply(PsiSubstitutor substitutor) {
     myT = substitutor.substitute(myT);
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; expr: " + myExpression.getText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/PsiMethodReferenceCompatibilityConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/PsiMethodReferenceCompatibilityConstraint.java
index 312f5a344519..11245cdca2ac 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/PsiMethodReferenceCompatibilityConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/PsiMethodReferenceCompatibilityConstraint.java
@@ -231,4 +231,9 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
   public void apply(PsiSubstitutor substitutor) {
     myT = substitutor.substitute(myT);
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; expr: " + myExpression.getText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/StrictSubtypingConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/StrictSubtypingConstraint.java
index db193ddda9eb..cef89a1bb0c3 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/StrictSubtypingConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/StrictSubtypingConstraint.java
@@ -141,4 +141,9 @@ public class StrictSubtypingConstraint implements ConstraintFormula {
     result = 31 * result + (myT != null ? myT.hashCode() : 0);
     return result;
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; myS: " + myS.getCanonicalText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/SubtypingConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/SubtypingConstraint.java
index d1218c9dae05..38c2c910e5b7 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/SubtypingConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/SubtypingConstraint.java
@@ -128,4 +128,9 @@ public class SubtypingConstraint implements ConstraintFormula {
       }
     }
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; myS: " + myS.getCanonicalText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeCompatibilityConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeCompatibilityConstraint.java
index d94aa94e9191..216b6fde5847 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeCompatibilityConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeCompatibilityConstraint.java
@@ -108,4 +108,9 @@ public class TypeCompatibilityConstraint implements ConstraintFormula {
     result = 31 * result + myS.hashCode();
     return result;
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; myS: " + myS.getCanonicalText();
+  }
 }
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeEqualityConstraint.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeEqualityConstraint.java
index cbb1db809c4a..5f94b2b1c433 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeEqualityConstraint.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/TypeEqualityConstraint.java
@@ -145,4 +145,9 @@ public class TypeEqualityConstraint implements ConstraintFormula {
     result = 31 * result + (myS != null ? myS.hashCode() : 0);
     return result;
   }
+
+  @Override
+  public String toString() {
+    return "T: " + myT.getCanonicalText() +"; myS: " + myS.getCanonicalText();
+  }
 }