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https://issues.apache.org/jira/browse/GROOVY-12469?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18130607#comment-18130607
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ASF GitHub Bot commented on GROOVY-12469:
-----------------------------------------
Copilot commented on code in PR #2999:
URL: https://github.com/apache/groovy/pull/2999#discussion_r4353749641
##########
src/main/java/org/codehaus/groovy/classgen/asm/BinaryExpressionHelper.java:
##########
@@ -1140,6 +1141,28 @@ protected void evaluateCompoundAssign(final String
assignName, final String base
controller.getCompileStack().popLHS();
}
+ /**
+ * The type chooser may give a declared variable a type narrower than its
+ * declared type (flow typing). When the value on the stack is not already
of
+ * that narrower type (for example, it was inferred from generics but the
+ * erased type is wider), casting to it could fail where the declared type
+ * would not, so the declared type is used instead. Uses of the variable
that
+ * rely on the narrower type cast at the point of use.
+ */
+ private static ClassNode declaredTypeIfNarrowingNotGuaranteed(final
VariableExpression var, final ClassNode lhsType, final ClassNode rhsType) {
+ ClassNode declaredType = var.getOriginType();
+ if (var.isDynamicTyped() || declaredType.equals(lhsType)
+ || ClassHelper.isPrimitiveType(declaredType) ||
ClassHelper.isPrimitiveType(lhsType) || ClassHelper.isPrimitiveType(rhsType)
+ || !isSubtype(lhsType, declaredType) || isSubtype(rhsType,
lhsType)) {
+ return lhsType;
+ }
+ return declaredType;
+ }
+
+ private static boolean isSubtype(final ClassNode type, final ClassNode
superType) {
+ return type.isDerivedFrom(superType) ||
type.implementsInterface(superType);
+ }
+
Review Comment:
`isSubtype` duplicates existing type-relation utilities and is a narrower
check than STC’s helpers. To keep subtype/assignability logic consistent across
the static compiler (and avoid subtle mismatches for arrays, placeholders,
traits, redirects, etc.), consider replacing `isSubtype(...)` with
`StaticTypeCheckingSupport.implementsInterfaceOrIsSubclassOf(...)` (or
`isAssignableTo(...)` if that’s the intended relation) and removing the local
helper.
> SC: static compilation inserts wrong cast, derived from generic return type
> when assigned to a variable
> -------------------------------------------------------------------------------------------------------
>
> Key: GROOVY-12469
> URL: https://issues.apache.org/jira/browse/GROOVY-12469
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 2.5.23, 3.0.25, 5.0.3, 4.0.33, 5.1.3, 6.0.0
> Reporter: Björn Kautler
> Priority: Major
>
> Given the following snippet:
> {code:groovy}
> import java.lang.annotation.Annotation
> import java.lang.annotation.Retention
> import java.lang.annotation.Target
> import groovy.transform.CompileStatic
> @CompileStatic
> <T extends Annotation> T getRetention(Class<T> clazz) {
> Target.getAnnotation(Target)
> }
> @CompileStatic
> def foo() {
> Annotation x = getRetention(Retention) /*as Annotation*/
> }
> foo().toString()
> {code}
> This compiles fine under all versions, but fails with a
> {{GroovyCastException}} in all versions.
>
> The generated byte-code under SC has a cast on {{Retention}} in this, even
> though the variable is of type {{Annotation}} explicitly.
> Commenting in the {{as Annotation}} cast makes it work.
> Removing the {{Annotation x =}} also makes it work.
> Removing the {{@CompileStatic}} or replacing it by {{@TypeChecked}} of course
> also makes it work.
>
> I'd say static-compilation should here not insert an unnecessary cast to
> {{{}Retention{}}}, but at most a cast to {{Annotation}} as that is, what the
> variable needs and which should be consistent with JVM type-erasure, and also
> with the variant without the variable. Even with the method returning
> {{Annotation}} instead of {{def}} it works just fine. Just if the method
> declares to return {{Retention}} explicitly, the cast exception comes, but
> then rightfully.
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