MixinExtras Expressions: Recreate `ClassInfo#getCommonSuperClassOrInt…

…erface`.

It's quite scuffed and often returns `Object` even when there is a suitable common interface, but what's important is that this matches the runtime logic.

src/main/kotlin/platform/mixin/expression/MEExpressionService.kt

@@ -22,9 +22,13 @@ package com.demonwav.mcdev.platform.mixin.expression
 
 import com.demonwav.mcdev.platform.mixin.util.toPsiType
 import com.demonwav.mcdev.util.descriptor
-import com.intellij.psi.GenericsUtil
+import com.intellij.openapi.project.Project
 import com.intellij.psi.JavaPsiFacade
+import com.intellij.psi.PsiClass
+import com.intellij.psi.PsiClassType
+import com.intellij.psi.PsiElementFactory
 import com.intellij.psi.PsiManager
+import com.intellij.psi.PsiType
 import com.llamalad7.mixinextras.expression.impl.ExpressionService
 import com.llamalad7.mixinextras.expression.impl.flow.FlowContext
 import org.objectweb.asm.Type
@@ -34,11 +38,39 @@ object MEExpressionService : ExpressionService() {
         ctx as MEFlowContext
         val elementFactory = JavaPsiFacade.getElementFactory(ctx.project)
         return Type.getType(
-            GenericsUtil.getLeastUpperBound(
-                type1.toPsiType(elementFactory),
-                type2.toPsiType(elementFactory),
-                PsiManager.getInstance(ctx.project)
-            )?.descriptor ?: error("Failed to merge types $type1 and $type2!")
+            getCommonSuperClass(
+                ctx.project,
+                type1.toPsiType(elementFactory) as PsiClassType,
+                type2.toPsiType(elementFactory) as PsiClassType
+            )?.descriptor ?: error("Could not intersect types $type1 and $type2!")
         )
     }
+
+    // Copied from ClassInfo
+    private fun getCommonSuperClass(
+        project: Project,
+        type1: PsiType,
+        type2: PsiType
+    ): PsiClassType? {
+        val left = (type1 as? PsiClassType)?.resolve() ?: return null
+        val right = (type2 as? PsiClassType)?.resolve() ?: return null
+
+        fun objectType() = PsiType.getJavaLangObject(PsiManager.getInstance(project), left.resolveScope)
+        fun PsiClass.type() = PsiElementFactory.getInstance(project).createType(this)
+
+        if (left.isInheritor(right, true)) {
+            return right.type()
+        }
+        if (right.isInheritor(left, true)) {
+            return left.type()
+        }
+        if (left.isInterface || right.isInterface) {
+            return objectType()
+        }
+
+        return generateSequence(left) { it.superClass }
+            .firstOrNull { right.isInheritor(it, true) }
+            ?.type()
+            ?: objectType()
+    }
 }