From 0dc21a78ee69d175b6c3422bcbfa41b539decacd Mon Sep 17 00:00:00 2001
From: Mumfrey <adam@eq2.co.uk>
Date: Fri, 25 Jun 2021 18:01:27 +0100
Subject: [PATCH] Fix some version checks to properly respect *major* class
 version

---
 .../asm/mixin/MixinEnvironment.java           | 11 ++++++++--
 .../transformer/MixinApplicatorStandard.java  |  6 +++++-
 .../mixin/transformer/MixinTargetContext.java | 21 ++++++++++++++++---
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java b/src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java
index 747443072..34bff3bb4 100644
--- a/src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java
+++ b/src/main/java/org/spongepowered/asm/mixin/MixinEnvironment.java
@@ -671,9 +671,9 @@ boolean isSupported() {
         
         private CompatibilityLevel maxCompatibleLevel;
         
-        private CompatibilityLevel(int ver, int classMajorVersion, int languageFeatures) {
+        private CompatibilityLevel(int ver, int classVersion, int languageFeatures) {
             this.ver = ver;
-            this.classVersion = classMajorVersion & 0xFF;
+            this.classVersion = classVersion;
             this.languageFeatures = languageFeatures;
         }
         
@@ -702,6 +702,13 @@ public int getClassVersion() {
             return this.classVersion;
         }
         
+        /**
+         * Get the major class version expected at this compatibility level
+         */
+        public int getClassMajorVersion() {
+            return this.classVersion & 0xFFFF;
+        }
+        
         /**
          * Get all supported language features
          */
diff --git a/src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java b/src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java
index 4bb7b5edc..dd2ef0e12 100644
--- a/src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java
+++ b/src/main/java/org/spongepowered/asm/mixin/transformer/MixinApplicatorStandard.java
@@ -434,7 +434,11 @@ protected void applyAttributes(MixinTargetContext mixin) {
         if (mixin.shouldSetSourceFile()) {
             this.targetClass.sourceFile = mixin.getSourceFile();
         }
-        this.targetClass.version = Math.max(this.targetClass.version, mixin.getMinRequiredClassVersion());
+        
+        int requiredVersion = mixin.getMinRequiredClassVersion();
+        if ((requiredVersion & 0xFFFF) > (this.targetClass.version & 0xFFFF)) {
+            this.targetClass.version = requiredVersion;
+        }
     }
 
     /**
diff --git a/src/main/java/org/spongepowered/asm/mixin/transformer/MixinTargetContext.java b/src/main/java/org/spongepowered/asm/mixin/transformer/MixinTargetContext.java
index ac9c05b2e..51f2077d2 100644
--- a/src/main/java/org/spongepowered/asm/mixin/transformer/MixinTargetContext.java
+++ b/src/main/java/org/spongepowered/asm/mixin/transformer/MixinTargetContext.java
@@ -1071,13 +1071,28 @@ FieldNode findRemappedField(FieldNode field) {
      * @param version version to require
      */
     protected void requireVersion(int version) {
-        this.minRequiredClassVersion = Math.max(this.minRequiredClassVersion, version);
+        int majorVersion = version & 0xFFFF;
+        int minorVersion = (version >> 16) & 0xFFFF;
+        
+        if (majorVersion <= (this.minRequiredClassVersion & 0xFFFF)) {
+            return;
+        }
+        
+        this.minRequiredClassVersion = version;
         
         // This validation is done on the mixin beforehand, however it's still
         // possible that an upstream transformer can inject unsupported
         // instructions without updating the class version.
-        if ((version & 0xFFFF) > ASM.getMaxSupportedClassVersionMajor()) {
-            throw new InvalidMixinException(this, "Unsupported mixin class version " + version);
+        if (majorVersion > ASM.getMaxSupportedClassVersionMajor()) {
+            throw new InvalidMixinException(this, String.format("Unsupported mixin class version %d.%d. ASM supports %s",
+                    majorVersion, minorVersion, ASM.getClassVersionString()));
+        }
+        
+        CompatibilityLevel compatibilityLevel = MixinEnvironment.getCompatibilityLevel();
+        if (majorVersion > compatibilityLevel.getClassMajorVersion()) {
+            MixinTargetContext.logger.warn(
+                    "{}: Class version {}.{} required is higher than the class version supported by the current compatibility level {} ",
+                    this, majorVersion, minorVersion, compatibilityLevel);
         }
     }