mixin: Avoid looking up target for Shadows with a single alias

Fixes #367

Author: stephan-gh

src/main/kotlin/com/demonwav/mcdev/platform/mixin/util/Shadow.kt

@@ -18,6 +18,7 @@ import com.demonwav.mcdev.util.findMatchingField
 import com.demonwav.mcdev.util.findMatchingMethod
 import com.demonwav.mcdev.util.findMatchingMethods
 import com.demonwav.mcdev.util.ifEmpty
+import com.demonwav.mcdev.util.isNotEmpty
 import com.demonwav.mcdev.util.mapFirstNotNull
 import com.intellij.psi.PsiAnnotation
 import com.intellij.psi.PsiArrayInitializerMemberValue
@@ -69,10 +70,7 @@ fun resolveShadowTargets(shadow: PsiAnnotation, targetClasses: Collection<PsiCla
     }
 }
 
-private fun hasAliases(shadow: PsiAnnotation): Boolean {
-    val aliases = shadow.findDeclaredAttributeValue("aliases") as? PsiArrayInitializerMemberValue ?: return false
-    return aliases.initializers.isNotEmpty()
-}
+private fun hasAliases(shadow: PsiAnnotation): Boolean = shadow.findDeclaredAttributeValue("aliases").isNotEmpty()
 
 @Contract(pure = true)
 private fun stripPrefix(shadow: PsiAnnotation, member: PsiMember): String? {

src/main/kotlin/com/demonwav/mcdev/util/annotation-utils.kt

@@ -49,6 +49,17 @@ fun PsiAnnotationMemberValue.resolveClass(): PsiClass? {
     return (operand.type as PsiClassType).resolve()
 }
 
+/**
+ * Returns `true` if the annotation value is present (not `null`) and
+ * initialized either to a single value or an array with at least one
+ * element.
+ *
+ * @return `true` if the annotation member is not empty
+ */
+fun PsiAnnotationMemberValue?.isNotEmpty(): Boolean {
+    return this != null && (this !is PsiArrayInitializerMemberValue || initializers.isNotEmpty())
+}
+
 @Contract(pure = true)
 private inline fun <T : Any> PsiAnnotationMemberValue.parseArray(func: (PsiAnnotationMemberValue) -> T?): List<T> {
     return if (this is PsiArrayInitializerMemberValue) {