Wrong ClassCastException with varargs of uninstantiable type.
If there is a vararg of an uninstatiable type Foo as in the following
example,
m(Foo... foos) {
...
}
fooArr = m();
the compiler might emit the following code for the call
fooArr = (null[]) /* inlined code for m() */;
Such call will fail at runtime as the compiler determines that Foo[]
can not be cast to null[].
Three options were considered.
1. Make a cast from Foo[] to null[] succeed if Foo is not
instantiable.
2. Make the JNewArray AST node by of type null[] if its base type
was not instantiable.
3. Don't model at all null[], i.e. don't let an array be tightned
to null[].
The drawbacks of 1 and 2 is loss of information by transforming casts
to different array classes to (null[]).
The drawback of 3 is potential increase in codesize which does not
seem to occurr in practice.
Bug: issue 8736.
Change-Id: I3348836b78ad59e11685a3a55650df81afa75269
diff --git a/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java b/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
index af202f4..ab8c418 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/ast/JProgram.java
@@ -575,7 +575,13 @@
*/
JReferenceType leafRefType1 = (JReferenceType) leafType1;
JReferenceType leafRefType2 = (JReferenceType) leafType2;
- JReferenceType leafGeneralization = generalizeTypes(leafRefType1, leafRefType2);
+
+ /**
+ * Never generalize arrays to arrays of {@link JNonNullType} as null array initialization
+ * is not accounted for in {@link TypeTightener}.
+ */
+ JReferenceType leafGeneralization =
+ generalizeTypes(leafRefType1, leafRefType2).getUnderlyingType();
return getTypeArray(leafGeneralization, dims1);
} else {
diff --git a/dev/core/src/com/google/gwt/dev/jjs/impl/ComputeCastabilityInformation.java b/dev/core/src/com/google/gwt/dev/jjs/impl/ComputeCastabilityInformation.java
index f77281a..1813d2d 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/impl/ComputeCastabilityInformation.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/impl/ComputeCastabilityInformation.java
@@ -167,20 +167,22 @@
type = type.getUnderlyingType();
qType = qType.getUnderlyingType();
+ if (program.typeOracle.canTriviallyCast(type, qType)) {
+ return true;
+ }
+
if (type instanceof JArrayType && qType instanceof JArrayType) {
JArrayType aType = (JArrayType) type;
JArrayType aqType = (JArrayType) qType;
- return program.typeOracle.canTriviallyCast(type, qType)
- || (program.isJavaScriptObject(aType.getLeafType()) && program
+ return (program.isJavaScriptObject(aType.getLeafType()) && program
.isJavaScriptObject(aqType.getLeafType()));
}
- return program.typeOracle.canTriviallyCast(type, qType)
- || (program.isJavaScriptObject(type) && program.isJavaScriptObject(qType));
+ return (program.isJavaScriptObject(type) && program.isJavaScriptObject(qType));
}
/**
- * Create the mapping from a class to its query types.
+ * Create the mapping from a class to the types it can be cast to.
*/
private void computeCastMap(JReferenceType type) {
if (type == null || alreadyRan.contains(type)) {
diff --git a/dev/core/src/com/google/gwt/dev/jjs/impl/TypeTightener.java b/dev/core/src/com/google/gwt/dev/jjs/impl/TypeTightener.java
index bbaa2db..836dc17 100644
--- a/dev/core/src/com/google/gwt/dev/jjs/impl/TypeTightener.java
+++ b/dev/core/src/com/google/gwt/dev/jjs/impl/TypeTightener.java
@@ -19,7 +19,6 @@
import com.google.gwt.dev.jjs.ast.CanBeAbstract;
import com.google.gwt.dev.jjs.ast.Context;
import com.google.gwt.dev.jjs.ast.JArrayRef;
-import com.google.gwt.dev.jjs.ast.JArrayType;
import com.google.gwt.dev.jjs.ast.JBinaryOperation;
import com.google.gwt.dev.jjs.ast.JBinaryOperator;
import com.google.gwt.dev.jjs.ast.JCastOperation;
@@ -687,20 +686,6 @@
return null;
}
- private JArrayType nullifyArrayType(JArrayType arrayType) {
- JType elementType = arrayType.getElementType();
- if (elementType instanceof JReferenceType) {
- JReferenceType refType = (JReferenceType) elementType;
- if (!program.typeOracle.isInstantiatedType(refType)) {
- return program.getTypeArray(JNullType.INSTANCE);
- } else if (elementType instanceof JArrayType) {
- JArrayType newElementType = nullifyArrayType((JArrayType) elementType);
- return program.getTypeArray(newElementType.getLeafType(), newElementType.getDims() + 1);
- }
- }
- return arrayType;
- }
-
/**
* Tighten based on assignment, and for parameters, callArgs as well.
*/
@@ -721,11 +706,6 @@
return;
}
- if (refType instanceof JArrayType) {
- JArrayType arrayType = (JArrayType) refType;
- refType = nullifyArrayType(arrayType);
- }
-
// tighten based on leaf types
JReferenceType leafType = getSingleConcreteType(refType);
if (leafType != null) {
diff --git a/user/test/com/google/gwt/dev/jjs/test/VarargsTest.java b/user/test/com/google/gwt/dev/jjs/test/VarargsTest.java
index f780cae..23e0a03 100644
--- a/user/test/com/google/gwt/dev/jjs/test/VarargsTest.java
+++ b/user/test/com/google/gwt/dev/jjs/test/VarargsTest.java
@@ -24,6 +24,8 @@
*/
public class VarargsTest extends GWTTestCase {
+ private static class Foo { }
+
@Override
public String getModuleName() {
return "com.google.gwt.dev.jjs.CompilerSuite";
@@ -59,10 +61,29 @@
assertTrue(Arrays.equals(expected, actual));
}
+ /**
+ * Test for issue 8736.
+ */
+ public void testNullEmptyUninstantiable_Varargs() {
+ assertNotNull(fooVararg());
+ }
+
+ public void testNullEmptyUninstantiable_NoVarargs() {
+ assertNotNull(fooIdent(new Foo[]{}));
+ }
+
private String[] vararg(String... args) {
return args;
}
+ private Foo[] fooVararg(Foo... args) {
+ return args;
+ }
+
+ private Foo[] fooIdent(Foo[] args) {
+ return args;
+ }
+
private int[] varargUnboxed(int... args) {
return args;
}
