Add inspection for calling a constructor in a mixin which doesn't exist in the target class

Author: Earthcomputer

src/main/kotlin/platform/mixin/inspection/MixinInstantiationWithinMixinInspection.kt

@@ -0,0 +1,82 @@
+/*
+ * Minecraft Development for IntelliJ
+ *
+ * https://mcdev.io/
+ *
+ * Copyright (C) 2026 minecraft-dev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, version 3.0 only.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.demonwav.mcdev.platform.mixin.inspection
+
+import com.demonwav.mcdev.platform.mixin.util.findMethod
+import com.demonwav.mcdev.platform.mixin.util.isMixin
+import com.demonwav.mcdev.platform.mixin.util.mixinTargets
+import com.demonwav.mcdev.util.MemberReference
+import com.demonwav.mcdev.util.descriptor
+import com.demonwav.mcdev.util.findContainingClass
+import com.intellij.codeInspection.ProblemsHolder
+import com.intellij.psi.JavaElementVisitor
+import com.intellij.psi.PsiClass
+import com.intellij.psi.PsiConstructorCall
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiEnumConstant
+import com.intellij.psi.PsiModifier
+import com.intellij.psi.PsiNewExpression
+
+class MixinInstantiationWithinMixinInspection : MixinInspection() {
+    override fun getStaticDescription() = "Reports when a mixin class is instantiated within that same class using a constructor which doesn't exist in the target class"
+
+    override fun buildVisitor(holder: ProblemsHolder) = object : JavaElementVisitor() {
+        override fun visitNewExpression(expression: PsiNewExpression) {
+            if (expression.isArrayCreation || expression.anonymousClass != null) {
+                return
+            }
+            val classReference = expression.classReference ?: return
+            val constructedClass = classReference.resolve() as? PsiClass ?: return
+            visitConstructorCall(expression, constructedClass, classReference)
+        }
+
+        override fun visitEnumConstant(enumConstant: PsiEnumConstant) {
+            val constructedClass = enumConstant.containingClass ?: return
+            visitConstructorCall(enumConstant, constructedClass, enumConstant.nameIdentifier)
+        }
+
+        private fun visitConstructorCall(constructorCall: PsiConstructorCall, constructedClass: PsiClass, problemElement: PsiElement) {
+            if (!constructedClass.isMixin || constructedClass != constructorCall.findContainingClass()) {
+                return
+            }
+            val resolvedConstructorDesc = constructorCall.resolveConstructor()?.descriptor ?: when {
+                constructedClass.isEnum -> "(Ljava/lang/String;)V"
+                !constructedClass.hasModifierProperty(PsiModifier.STATIC) && constructedClass.containingClass != null ->
+                    "(${constructedClass.containingClass!!.descriptor})V"
+                else -> "()V"
+            }
+
+            val constructorExistsInAllTargets = constructedClass.mixinTargets.all {
+                it.findMethod(
+                    MemberReference(
+                        "<init>",
+                        resolvedConstructorDesc
+                    )
+                ) != null
+            }
+            if (constructorExistsInAllTargets) {
+                return
+            }
+
+            holder.registerProblem(problemElement, "Constructor does not exist in target class")
+        }
+    }
+}

src/main/resources/META-INF/plugin.xml

@@ -1122,6 +1122,14 @@
                          level="ERROR"
                          hasStaticDescription="true"
                          implementationClass="com.demonwav.mcdev.platform.mixin.inspection.EnumMixinSwitchStatementInspection"/>
+        <localInspection displayName="Mixin instantiated within that same mixin using a constructor which doesn't exist"
+                         shortName="MixinConstructorDoesntExist"
+                         groupName="Mixin"
+                         language="JAVA"
+                         enabledByDefault="true"
+                         level="ERROR"
+                         hasStaticDescription="true"
+                         implementationClass="com.demonwav.mcdev.platform.mixin.inspection.MixinInstantiationWithinMixinInspection"/>
         <localInspection displayName="Inner classes in Mixins"
                          shortName="MixinInnerClass"
                          groupName="Mixin"