Fix: Fix interface injector visibility checks.

src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java

@@ -1080,7 +1080,17 @@ static String getSupportedVersions() {
             }
             return sb.toString();
         }
-
+
+        public static CompatibilityLevel forClassVersion(int version) {
+            CompatibilityLevel latest = null;
+            for (CompatibilityLevel level : values()) {
+                if (level.getClassVersion() >= version) {
+                    return level;
+                }
+                latest = level;
+            }
+            return latest;
+        }
     }
 
     /**

src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorInterface.java

@@ -24,20 +24,17 @@
  */
 package org.spongepowered.asm.mixin.transformer;
 
-import java.lang.reflect.Modifier;
 import java.util.Map.Entry;
 
 import org.objectweb.asm.tree.FieldNode;
 import org.objectweb.asm.tree.MethodNode;
-import org.spongepowered.asm.mixin.MixinEnvironment;
 import org.spongepowered.asm.mixin.MixinEnvironment.Feature;
 import org.spongepowered.asm.mixin.injection.struct.InjectionInfo;
 import org.spongepowered.asm.mixin.injection.throwables.InvalidInjectionException;
 import org.spongepowered.asm.mixin.transformer.ClassInfo.Field;
 import org.spongepowered.asm.mixin.transformer.throwables.InvalidInterfaceMixinException;
 import org.spongepowered.asm.util.Annotations;
 import org.spongepowered.asm.util.Constants;
-import org.spongepowered.asm.util.LanguageFeatures;
 
 /**
  * Applicator for interface mixins, mainly just disables things which aren't
@@ -166,17 +163,4 @@ protected void applyInjections(MixinTargetContext mixin, int injectorOrder) {
             return;
         }
     }
-
-    @Override
-    protected void checkMethodVisibility(MixinTargetContext mixin, MethodNode mixinMethod) {
-        //Allow injecting into static interface methods where it isn't possible to control the access of the injection method
-        if (Modifier.isStatic(mixinMethod.access) && !MixinEnvironment.getCompatibilityLevel().supports(LanguageFeatures.PRIVATE_METHODS_IN_INTERFACES)) {
-            InjectionInfo injectInfo = InjectionInfo.parse(mixin, mixinMethod);
-            if (injectInfo != null) {
-                return;
-            }
-        }
-
-        super.checkMethodVisibility(mixin, mixinMethod);
-    }
 }

src/main/java/org/spongepowered/asm/mixin/transformer/MixinInfo.java

@@ -1268,6 +1268,10 @@ List<ClassInfo> getTargets() {
     Set<String> getInterfaces() {
         return this.getState().getInterfaces();
     }
+
+    int getClassVersion() {
+        return this.getState().getClassNode().version;
+    }
 
     /**
      * Get transformer extensions

src/main/java/org/spongepowered/asm/mixin/transformer/MixinPreProcessorInterface.java

@@ -108,10 +108,11 @@ protected void prepareMethod(MixinMethodNode mixinMethod, Method method) {
                     method, this.mixin));
         }
 
-        // Make injectors private synthetic if the current runtime supports it
+        CompatibilityLevel classLevel = CompatibilityLevel.forClassVersion(mixin.getClassVersion());
+        // Make injectors private synthetic if the current class version supports it
         if (isPublic
-                && !currentLevel.supports(LanguageFeatures.PRIVATE_METHODS_IN_INTERFACES)
-                && currentLevel.supports(LanguageFeatures.PRIVATE_SYNTHETIC_METHODS_IN_INTERFACES)) {
+                && !classLevel.supports(LanguageFeatures.PRIVATE_METHODS_IN_INTERFACES)
+                && classLevel.supports(LanguageFeatures.PRIVATE_SYNTHETIC_METHODS_IN_INTERFACES)) {
             Bytecode.setVisibility(mixinMethod, Bytecode.Visibility.PRIVATE);
             mixinMethod.access |= Opcodes.ACC_SYNTHETIC;
         }