Constraint priorities introduced. Not used for the time being

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/CallResolver.java

@@ -29,6 +29,9 @@ import static org.jetbrains.jet.lang.resolve.BindingContext.*;
 import static org.jetbrains.jet.lang.resolve.calls.ResolutionStatus.*;
 import static org.jetbrains.jet.lang.resolve.calls.ResolvedCallImpl.MAP_TO_CANDIDATE;
 import static org.jetbrains.jet.lang.resolve.calls.ResolvedCallImpl.MAP_TO_RESULT;
+import static org.jetbrains.jet.lang.resolve.calls.inference.ConstraintType.EXPECTED_TYPE;
+import static org.jetbrains.jet.lang.resolve.calls.inference.ConstraintType.RECEIVER;
+import static org.jetbrains.jet.lang.resolve.calls.inference.ConstraintType.VALUE_ARGUMENT;
 import static org.jetbrains.jet.lang.resolve.scopes.receivers.ReceiverDescriptor.NO_RECEIVER;
 import static org.jetbrains.jet.lang.types.TypeUtils.NO_EXPECTED_TYPE;
 
@@ -465,7 +468,7 @@ public class CallResolver {
                             ExpressionTypingServices temporaryServices = new ExpressionTypingServices(semanticServices, traceForUnknown);
                             JetType type = temporaryServices.getType(scope, expression, substituteDontCare.substitute(valueParameterDescriptor.getOutType(), Variance.INVARIANT));
                             if (type != null) {
-                                constraintSystem.addSubtypingConstraint(type, effectiveExpectedType);
+                                constraintSystem.addSubtypingConstraint(VALUE_ARGUMENT.assertSubtyping(type, effectiveExpectedType));
                             }
                             else {
                                 candidateCall.argumentHasNoType();
@@ -478,12 +481,12 @@ public class CallResolver {
                     ReceiverDescriptor receiverArgument = candidateCall.getReceiverArgument();
                     ReceiverDescriptor receiverParameter = candidateWithFreshVariables.getReceiverParameter();
                     if (receiverArgument.exists() && receiverParameter.exists()) {
-                        constraintSystem.addSubtypingConstraint(receiverArgument.getType(), receiverParameter.getType());
+                        constraintSystem.addSubtypingConstraint(RECEIVER.assertSubtyping(receiverArgument.getType(), receiverParameter.getType()));
                     }
 
                     // Return type
                     if (expectedType != NO_EXPECTED_TYPE) {
-                        constraintSystem.addSubtypingConstraint(candidateWithFreshVariables.getReturnType(), expectedType);
+                        constraintSystem.addSubtypingConstraint(EXPECTED_TYPE.assertSubtyping(candidateWithFreshVariables.getReturnType(), expectedType));
                     }
 
                     // Solution

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystem.java

@@ -2,7 +2,6 @@ package org.jetbrains.jet.lang.resolve.calls.inference;
 
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.lang.descriptors.TypeParameterDescriptor;
-import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.Variance;
 
 /**
@@ -11,7 +10,7 @@ import org.jetbrains.jet.lang.types.Variance;
 public interface ConstraintSystem {
     void registerTypeVariable(@NotNull TypeParameterDescriptor typeParameterDescriptor, @NotNull Variance positionVariance);
 
-    void addSubtypingConstraint(@NotNull JetType lower, @NotNull JetType upper);
+    void addSubtypingConstraint(@NotNull SubtypingConstraint constraint);
 
     @NotNull
     ConstraintSystemSolution solve();

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java

@@ -382,9 +382,9 @@ public class ConstraintSystemImpl implements ConstraintSystem {
     }
 
     @Override
-    public void addSubtypingConstraint(@NotNull JetType lower, @NotNull JetType upper) {
+    public void addSubtypingConstraint(@NotNull SubtypingConstraint constraint) {
-        TypeValue typeValueForLower = getTypeValueFor(lower);
+        TypeValue typeValueForLower = getTypeValueFor(constraint.getSubtype());
-        TypeValue typeValueForUpper = getTypeValueFor(upper);
+        TypeValue typeValueForUpper = getTypeValueFor(constraint.getSupertype());
         addSubtypingConstraintOnTypeValues(typeValueForLower, typeValueForUpper);
     }
 
@@ -415,8 +415,16 @@ public class ConstraintSystemImpl implements ConstraintSystem {
                 }
             }
 
-            // Lower bounds?
+            for (TypeValue lowerBound : typeValue.getLowerBounds()) {
-
+                if (lowerBound instanceof KnownType) {
+                    KnownType knownBoundType = (KnownType) lowerBound;
+                    boolean ok = constraintExpander.isSubtypeOf(knownBoundType.getType(), jetType);
+                    if (!ok) {
+                        listener.error("Error while expanding '" + knownBoundType.getType() + " :< " + jetType + "'");
+                        return new Solution().registerError("Mismatch while expanding constraints");
+                    }
+                }
+            }
         }
 
         // Fill in upper bounds from type parameter bounds

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintType.java

@@ -0,0 +1,35 @@
+package org.jetbrains.jet.lang.resolve.calls.inference;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.types.JetType;
+
+import java.text.MessageFormat;
+
+/**
+ * @author abreslav
+ */
+public enum ConstraintType implements Comparable<ConstraintType> {
+    // The order of these constants DOES matter
+    // they are compared according to ordinal() values
+    // First element has the highest priority
+    RECEIVER("{0} is not a subtype of the expected receiver type {1}"),
+    VALUE_ARGUMENT("Type mismatch: argument type is {0}, but {1} was expected"),
+    EXPECTED_TYPE("Resulting type is {0} but {1} was expected"),
+    PARAMETER_BOUND("Type parameter bound is not satisfied: {0} is not a subtype of {1}");
+
+    private final String errorMessageTemplate; // {0} is subtype, {1} is supertye
+
+    private ConstraintType(@NotNull String errorMessageTemplate) {
+        this.errorMessageTemplate = errorMessageTemplate;
+    }
+
+    @NotNull
+    public SubtypingConstraint assertSubtyping(@NotNull JetType subtype, @NotNull JetType supertype) {
+        return new SubtypingConstraint(this, subtype, supertype);
+    }
+
+    @NotNull
+    public String makeErrorMessage(@NotNull SubtypingConstraint constraint) {
+        return MessageFormat.format(errorMessageTemplate, constraint.getSubtype(), constraint.getSupertype());
+    }
+}

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/SubtypingConstraint.java

@@ -0,0 +1,39 @@
+package org.jetbrains.jet.lang.resolve.calls.inference;
+
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.jet.lang.types.JetType;
+
+/**
+ * @author abreslav
+ */
+public class SubtypingConstraint {
+    private final ConstraintType type;
+    private final JetType subtype;
+    private final JetType supertype;
+
+    public SubtypingConstraint(@NotNull ConstraintType type, @NotNull JetType subtype, @NotNull JetType supertype) {
+        this.type = type;
+        this.subtype = subtype;
+        this.supertype = supertype;
+    }
+
+    @NotNull
+    public JetType getSubtype() {
+        return subtype;
+    }
+
+    @NotNull
+    public JetType getSupertype() {
+        return supertype;
+    }
+
+    @NotNull
+    public ConstraintType getType() {
+        return type;
+    }
+
+    @NotNull
+    public String getErrorMessage() {
+        return type.makeErrorMessage(this);
+    }
+}