Assertions on approximation of platform types to non-null types

- for most expressions (ExpressionCodegen.genQualified)

compiler/backend/src/org/jetbrains/jet/codegen/AsmUtil.java

@@ -37,7 +37,9 @@ import org.jetbrains.jet.lang.resolve.java.*;
 import org.jetbrains.jet.lang.resolve.java.descriptor.JavaCallableMemberDescriptor;
 import org.jetbrains.jet.lang.resolve.kotlin.PackagePartClassUtils;
 import org.jetbrains.jet.lang.resolve.name.FqName;
+import org.jetbrains.jet.lang.types.Approximation;
 import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.TypesPackage;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 import org.jetbrains.jet.lexer.JetTokens;
 import org.jetbrains.org.objectweb.asm.*;
@@ -608,12 +610,15 @@ public class AsmUtil {
             @NotNull CallableDescriptor descriptor,
             @NotNull String assertMethodToCall
     ) {
+        // Assertions are generated elsewhere for platform types
+        if (JavaPackage.getPLATFORM_TYPES()) return;
+
         if (!state.isCallAssertionsEnabled()) return;
 
         if (!isDeclaredInJava(descriptor)) return;
 
         JetType type = descriptor.getReturnType();
-        if (type == null || isNullableType(type)) return;
+        if (type == null || isNullableType(TypesPackage.lowerIfFlexible(type))) return;
 
         Type asmType = state.getTypeMapper().mapReturnType(descriptor);
         if (asmType.getSort() == Type.OBJECT || asmType.getSort() == Type.ARRAY) {
@@ -625,6 +630,30 @@ public class AsmUtil {
         }
     }
 
+    @NotNull
+    public static StackValue genNotNullAssertions(
+            @NotNull GenerationState state,
+            @NotNull final StackValue stackValue,
+            @Nullable final Approximation.Info approximationInfo
+    ) {
+        if (!state.isCallAssertionsEnabled()) return stackValue;
+        if (approximationInfo == null || !TypesPackage.assertNotNull(approximationInfo)) return stackValue;
+
+        return new StackValue(stackValue.type) {
+
+            @Override
+            public void put(Type type, InstructionAdapter v) {
+                stackValue.put(type, v);
+                if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
+                    v.dup();
+                    v.visitLdcInsn(approximationInfo.getMessage());
+                    v.invokestatic("kotlin/jvm/internal/Intrinsics", "checkExpressionValueIsNotNull",
+                                   "(Ljava/lang/Object;Ljava/lang/String;)V", false);
+                }
+            }
+        };
+    }
+
     private static boolean isDeclaredInJava(@NotNull CallableDescriptor callableDescriptor) {
         CallableDescriptor descriptor = callableDescriptor;
         while (true) {

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -61,6 +61,7 @@ import org.jetbrains.jet.lang.resolve.java.descriptor.SamConstructorDescriptor;
 import org.jetbrains.jet.lang.resolve.java.jvmSignature.JvmMethodSignature;
 import org.jetbrains.jet.lang.resolve.name.Name;
 import org.jetbrains.jet.lang.resolve.scopes.receivers.*;
+import org.jetbrains.jet.lang.types.Approximation;
 import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.TypeUtils;
 import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
@@ -242,7 +243,14 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
                 }
             }
 
-            return selector.accept(visitor, receiver);
+            StackValue stackValue = selector.accept(visitor, receiver);
+
+            Approximation.Info approximationInfo = null;
+            if (selector instanceof JetExpression) {
+                approximationInfo = bindingContext.get(BindingContext.EXPRESSION_RESULT_APPROXIMATION, (JetExpression) selector);
+            }
+
+            return genNotNullAssertions(state, stackValue, approximationInfo);
         }
         catch (ProcessCanceledException e) {
             throw e;

compiler/frontend/src/org/jetbrains/jet/lang/resolve/BindingContext.java

@@ -35,6 +35,7 @@ import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.resolve.name.FqNameUnsafe;
 import org.jetbrains.jet.lang.resolve.scopes.JetScope;
 import org.jetbrains.jet.lang.resolve.scopes.receivers.Qualifier;
+import org.jetbrains.jet.lang.types.Approximation;
 import org.jetbrains.jet.lang.types.DeferredType;
 import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.expressions.CaptureKind;
@@ -83,6 +84,7 @@ public interface BindingContext {
     WritableSlice<JetExpression, JetType> EXPRESSION_TYPE = new BasicWritableSlice<JetExpression, JetType>(DO_NOTHING);
     WritableSlice<JetExpression, JetType> EXPECTED_EXPRESSION_TYPE = new BasicWritableSlice<JetExpression, JetType>(DO_NOTHING);
     WritableSlice<JetExpression, DataFlowInfo> EXPRESSION_DATA_FLOW_INFO = new BasicWritableSlice<JetExpression, DataFlowInfo>(DO_NOTHING);
+    WritableSlice<JetExpression, Approximation.Info> EXPRESSION_RESULT_APPROXIMATION = new BasicWritableSlice<JetExpression, Approximation.Info>(DO_NOTHING);
     WritableSlice<JetExpression, DataFlowInfo> DATAFLOW_INFO_AFTER_CONDITION = Slices.createSimpleSlice();
 
     /**

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/DataFlowUtils.java

@@ -17,6 +17,7 @@
 package org.jetbrains.jet.lang.types.expressions;
 
 import com.intellij.openapi.util.Ref;
+import com.intellij.openapi.util.text.StringUtil;
 import com.intellij.psi.tree.IElementType;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -33,13 +34,13 @@ import org.jetbrains.jet.lang.resolve.calls.smartcasts.SmartCastUtils;
 import org.jetbrains.jet.lang.resolve.constants.CompileTimeConstant;
 import org.jetbrains.jet.lang.resolve.constants.CompileTimeConstantChecker;
 import org.jetbrains.jet.lang.resolve.constants.IntegerValueTypeConstant;
-import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.*;
-import org.jetbrains.jet.lang.types.JetTypeInfo;
-import org.jetbrains.jet.lang.types.TypeUtils;
 import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 import org.jetbrains.jet.lexer.JetTokens;
 
+import java.util.Set;
+
 import static org.jetbrains.jet.lang.diagnostics.Errors.*;
 import static org.jetbrains.jet.lang.resolve.calls.context.ContextDependency.INDEPENDENT;
 import static org.jetbrains.jet.lang.types.TypeUtils.*;
@@ -157,14 +158,47 @@ public class DataFlowUtils {
     }
 
     @Nullable
-    public static JetType checkType(@Nullable JetType expressionType, @NotNull JetExpression expressionToCheck,
+    public static JetType checkType(@Nullable final JetType expressionType, @NotNull JetExpression expressionToCheck,
-            @NotNull JetType expectedType, @NotNull DataFlowInfo dataFlowInfo, @NotNull BindingTrace trace
+            @NotNull JetType expectedType, @NotNull final DataFlowInfo dataFlowInfo, @NotNull final BindingTrace trace
     ) {
-        JetExpression expression = JetPsiUtil.safeDeparenthesize(expressionToCheck, false);
+        final JetExpression expression = JetPsiUtil.safeDeparenthesize(expressionToCheck, false);
         recordExpectedType(trace, expression, expectedType);
 
-        if (expressionType == null || noExpectedType(expectedType) || !expectedType.getConstructor().isDenotable() ||
+        if (expressionType == null) return null;
+
+        if (noExpectedType(expectedType) || !expectedType.getConstructor().isDenotable() ||
             JetTypeChecker.DEFAULT.isSubtypeOf(expressionType, expectedType)) {
+
+            if (!noExpectedType(expectedType)) {
+                Approximation.Info approximationInfo = TypesPackage.getApproximationTo(expressionType, expectedType,
+                        new Approximation.DataFlowExtras() {
+                            private DataFlowValue getDataFlowValue() {
+                                return DataFlowValueFactory.createDataFlowValue(expression, expressionType, trace.getBindingContext());
+                            }
+
+                            @Override
+                            public boolean getCanBeNull() {
+                                return dataFlowInfo.getNullability(getDataFlowValue()).canBeNull();
+                            }
+
+                            @NotNull
+                            @Override
+                            public Set<JetType> getPossibleTypes() {
+                                return dataFlowInfo.getPossibleTypes(getDataFlowValue());
+                            }
+
+                            @NotNull
+                            @Override
+                            public String getPresentableText() {
+                                return StringUtil.trimMiddle(expression.getText(), 50);
+                            }
+                        }
+                );
+                if (approximationInfo != null) {
+                    trace.record(BindingContext.EXPRESSION_RESULT_APPROXIMATION, expression, approximationInfo);
+                }
+            }
+
             return expressionType;
         }
 
@@ -178,6 +212,7 @@ public class DataFlowUtils {
         }
 
         DataFlowValue dataFlowValue = DataFlowValueFactory.createDataFlowValue(expression, expressionType, trace.getBindingContext());
+
         for (JetType possibleType : dataFlowInfo.getPossibleTypes(dataFlowValue)) {
             if (JetTypeChecker.DEFAULT.isSubtypeOf(possibleType, expectedType)) {
                 SmartCastUtils.recordCastOrError(expression, possibleType, trace, dataFlowValue.isStableIdentifier(), false);

compiler/testData/codegen/notNullAssertions/A.java

@@ -32,4 +32,14 @@ public class A {
     public Object get(Object o) {
         return null;
     }
+
+    public A a() { return this; }
+
+    public static class B {
+        public static B b() { return null; }
+    }
+
+    public static class C {
+        public static C c() { return null; }
+    }
 }

compiler/testData/codegen/notNullAssertions/AssertionChecker.kt

@@ -1,5 +1,5 @@
 class AssertionChecker(val illegalStateExpected: Boolean) {
-    fun invoke(name: String, f: () -> Unit) {
+    fun invoke(name: String, f: () -> Any) {
         try {
             f()
         } catch (e: IllegalStateException) {
@@ -44,15 +44,32 @@ fun checkAssertions(illegalStateExpected: Boolean) {
     // binary expression
     check("plus") { A() + A() }
     
-    // postfix expression
-    check("inc") { var a = A(); a++ }
-    
-    // prefix expression
-    check("inc") { var a = A(); ++a }
-    
     // field
-    check("NULL") { val a = A().NULL }
+    check("NULL") { A().NULL }
     
     // static field
-    check("STATIC_NULL") { val a = A.STATIC_NULL }
+    check("STATIC_NULL") { A.STATIC_NULL }
+
+    // postfix expression
+    // TODO:
+//    check("inc") { var a = A().a(); a++ }
+
+    // prefix expression
+    check("inc-b") { var a = A.B.b(); a++ }
+
+    // prefix expression
+    check("inc-c") { var a = A.C.c(); a++ }
+
+    // prefix expression
+    check("inc") { var a = A().a(); ++a }
+
+    // prefix expression
+    check("inc-b") { var a = A.B.b(); ++a }
+
+    // prefix expression
+    // TODO:
+//    check("inc-c") { var a = A.C.c(); ++a }
 }
+
+fun A.C.inc(): A.C = A.C()
+fun <T> T.inc(): T = null as T

compiler/testData/codegen/notNullAssertions/arrayListGet.kt

@@ -1,8 +1,8 @@
 import java.util.ArrayList
 
-fun foo() {
+fun foo(): Any {
     val a = ArrayList<String>()
-    a.get(0)
+    return a.get(0)
 }
 
 fun bar(a: ArrayList<String>) {

compiler/tests/org/jetbrains/jet/codegen/GenerateNotNullAssertionsTest.java

@@ -120,7 +120,7 @@ public class GenerateNotNullAssertionsTest extends CodegenTestCase {
         loadFile("notNullAssertions/arrayListGet.kt");
         String text = generateToText();
 
-        assertTrue(text.contains("checkReturnedValueIsNotNull"));
+        assertTrue(text.contains("checkExpressionValueIsNotNull"));
         assertTrue(text.contains("checkParameterIsNotNull"));
     }
 
@@ -131,7 +131,7 @@ public class GenerateNotNullAssertionsTest extends CodegenTestCase {
         loadFile("notNullAssertions/javaMultipleSubstitutions.kt");
         String text = generateToText();
 
-        assertEquals(3, StringUtil.getOccurrenceCount(text, "checkReturnedValueIsNotNull"));
+        assertEquals(3, StringUtil.getOccurrenceCount(text, "checkExpressionValueIsNotNull"));
         assertEquals(3, StringUtil.getOccurrenceCount(text, "checkParameterIsNotNull"));
     }
 

core/descriptors/src/org/jetbrains/jet/lang/types/flexibleTypes.kt

@@ -17,6 +17,7 @@
 package org.jetbrains.jet.lang.types
 
 import org.jetbrains.jet.lang.types.checker.JetTypeChecker
+import org.jetbrains.jet.lang.types.Approximation.DataFlowExtras
 
 public trait Flexibility : TypeCapability {
     // lowerBound is a subtype of upperBound
@@ -29,15 +30,49 @@ public fun JetType.isFlexible(): Boolean = this.getCapability(javaClass<Flexibil
 public fun JetType.flexibility(): Flexibility = this.getCapability(javaClass<Flexibility>())!!
 
 public fun JetType.lowerIfFlexible(): JetType = if (this.isFlexible()) this.flexibility().getLowerBound() else this
+public fun JetType.upperIfFlexible(): JetType = if (this.isFlexible()) this.flexibility().getUpperBound() else this
 
 public trait NullAwareness : TypeCapability {
     public fun makeNullableAsSpecified(nullable: Boolean): JetType
 }
 
+public trait Approximation : TypeCapability {
+    public class Info(val from: JetType, val to: JetType, val message: String)
+    public trait DataFlowExtras {
+        object EMPTY : DataFlowExtras {
+            override val canBeNull: Boolean get() = true
+            override val possibleTypes: Set<JetType> get() = setOf()
+            override val presentableText: String = "<unknown>"
+        }
+
+        class OnlyMessage(message: String) : DataFlowExtras {
+            override val canBeNull: Boolean get() = true
+            override val possibleTypes: Set<JetType> get() = setOf()
+            override val presentableText: String = message
+        }
+
+        val canBeNull: Boolean
+        val possibleTypes: Set<JetType>
+        val presentableText: String
+    }
+
+    public fun approximateToExpectedType(expectedType: JetType, dataFlowExtras: DataFlowExtras): Info?
+}
+
+fun Approximation.Info.assertNotNull(): Boolean {
+    return from.upperIfFlexible().isNullable() && !TypeUtils.isNullableType(to)
+}
+
+public fun JetType.getApproximationTo(
+        expectedType: JetType,
+        extras: Approximation.DataFlowExtras = Approximation.DataFlowExtras.EMPTY
+): Approximation.Info? = this.getCapability(javaClass<Approximation>())?.approximateToExpectedType(expectedType, extras)
+
+
 public open class DelegatingFlexibleType protected (
         private val _lowerBound: JetType,
         private val _upperBound: JetType
-) : DelegatingType(), NullAwareness, Flexibility {
+) : DelegatingType(), NullAwareness, Flexibility, Approximation {
     class object {
         public fun create(lowerBound: JetType, upperBound: JetType): JetType {
             if (lowerBound == upperBound) return lowerBound
@@ -65,6 +100,20 @@ public open class DelegatingFlexibleType protected (
         return create(TypeUtils.makeNullableAsSpecified(_lowerBound, nullable), TypeUtils.makeNullableAsSpecified(_upperBound, nullable))
     }
 
+    override fun approximateToExpectedType(expectedType: JetType, dataFlowExtras: Approximation.DataFlowExtras): Approximation.Info? {
+        // val foo: Any? = foo() : Foo!
+        if (JetTypeChecker.DEFAULT.isSubtypeOf(getUpperBound(), expectedType)) return null
+
+        // if (foo : Foo! != null) {
+        //     val bar: Any = foo
+        // }
+        if (!dataFlowExtras.canBeNull && JetTypeChecker.DEFAULT.isSubtypeOf(TypeUtils.makeNotNullable(getUpperBound()), expectedType)) return null
+
+        // TODO: maybe check possibleTypes to avoid extra approximations
+
+        return Approximation.Info(this, expectedType, dataFlowExtras.presentableText)
+    }
+
     override fun getDelegate() = _lowerBound
 
     override fun toString() = "('$_lowerBound'..'$_upperBound')"

core/runtime.jvm/src/kotlin/jvm/internal/Intrinsics.java

@@ -37,6 +37,13 @@ public class Intrinsics {
         throw new KotlinNullPointerException();
     }
 
+    public static void checkExpressionValueIsNotNull(Object value, String message) {
+        if (value == null) {
+            IllegalStateException exception = new IllegalStateException(message + " must not be null");
+            throw sanitizeStackTrace(exception);
+        }
+    }
+
     public static void checkReturnedValueIsNotNull(Object value, String className, String methodName) {
         if (value == null) {
             IllegalStateException exception =

spec-docs/flexible-java-types.md

@@ -103,3 +103,15 @@ val arr: Array<Bar> = javaArrayMethod() // assert value "is Bar[]"
 `a++` stands for `a = a.inc()`, so
 - check a to satisfy the `a.inc()` conditions for receiver
 - check `a.inc()` result for assignability to `a`
+
+## Assertion Generation
+
+Constructs in question: anything that provides an expected type, i.e.
+ - assignments
+ - parameter default values
+ - delegation by: supertypes and properties
+ - dereferencing: x.foo
+ - all kinds of calls (foo, foo(), x[], x foo y, x + y, x++, x += 3, for loop, multi-declarations, invoke-convention, ...)
+ - explicit expected type (foo: Bar)
+ - for booleans: if (foo), foo || bar, foo && bar (!foo is a call)
+ - argument of throw