diff --git a/spring-core/src/main/java/org/springframework/asm/AnnotationVisitor.java b/spring-core/src/main/java/org/springframework/asm/AnnotationVisitor.java
index c3c236aefab..05b4f9ba2f6 100644
--- a/spring-core/src/main/java/org/springframework/asm/AnnotationVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/AnnotationVisitor.java
@@ -55,7 +55,7 @@ public abstract class AnnotationVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of the {@code
    *     ASM}<i>x</i> values in {@link Opcodes}.
    */
-  public AnnotationVisitor(final int api) {
+  protected AnnotationVisitor(final int api) {
     this(api, null);
   }
 
@@ -67,7 +67,7 @@ public abstract class AnnotationVisitor {
    * @param annotationVisitor the annotation visitor to which this visitor must delegate method
    *     calls. May be {@literal null}.
    */
-  public AnnotationVisitor(final int api, final AnnotationVisitor annotationVisitor) {
+  protected AnnotationVisitor(final int api, final AnnotationVisitor annotationVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
         && api != Opcodes.ASM7
diff --git a/spring-core/src/main/java/org/springframework/asm/ByteVector.java b/spring-core/src/main/java/org/springframework/asm/ByteVector.java
index 6187c1e22c7..1c4b9f7e3c6 100644
--- a/spring-core/src/main/java/org/springframework/asm/ByteVector.java
+++ b/spring-core/src/main/java/org/springframework/asm/ByteVector.java
@@ -65,6 +65,15 @@ public class ByteVector {
     this.length = data.length;
   }
 
+  /**
+   * Returns the actual number of bytes in this vector.
+   *
+   * @return the actual number of bytes in this vector.
+   */
+  public int size() {
+    return length;
+  }
+
   /**
    * Puts a byte into this byte vector. The byte vector is automatically enlarged if necessary.
    *
diff --git a/spring-core/src/main/java/org/springframework/asm/ClassVisitor.java b/spring-core/src/main/java/org/springframework/asm/ClassVisitor.java
index 05b448321af..14064e742e1 100644
--- a/spring-core/src/main/java/org/springframework/asm/ClassVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/ClassVisitor.java
@@ -54,7 +54,7 @@ public abstract class ClassVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of the {@code
    *     ASM}<i>x</i> values in {@link Opcodes}.
    */
-  public ClassVisitor(final int api) {
+  protected ClassVisitor(final int api) {
     this(api, null);
   }
 
@@ -66,7 +66,7 @@ public abstract class ClassVisitor {
    * @param classVisitor the class visitor to which this visitor must delegate method calls. May be
    *     null.
    */
-  public ClassVisitor(final int api, final ClassVisitor classVisitor) {
+  protected ClassVisitor(final int api, final ClassVisitor classVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
         && api != Opcodes.ASM7
diff --git a/spring-core/src/main/java/org/springframework/asm/FieldVisitor.java b/spring-core/src/main/java/org/springframework/asm/FieldVisitor.java
index 727417045fa..2aa16bc8e61 100644
--- a/spring-core/src/main/java/org/springframework/asm/FieldVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/FieldVisitor.java
@@ -51,7 +51,7 @@ public abstract class FieldVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of the {@code
    *     ASM}<i>x</i> values in {@link Opcodes}.
    */
-  public FieldVisitor(final int api) {
+  protected FieldVisitor(final int api) {
     this(api, null);
   }
 
@@ -63,7 +63,7 @@ public abstract class FieldVisitor {
    * @param fieldVisitor the field visitor to which this visitor must delegate method calls. May be
    *     null.
    */
-  public FieldVisitor(final int api, final FieldVisitor fieldVisitor) {
+  protected FieldVisitor(final int api, final FieldVisitor fieldVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
         && api != Opcodes.ASM7
diff --git a/spring-core/src/main/java/org/springframework/asm/MethodVisitor.java b/spring-core/src/main/java/org/springframework/asm/MethodVisitor.java
index 15ca4a5e4eb..35ecb14c4e1 100644
--- a/spring-core/src/main/java/org/springframework/asm/MethodVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/MethodVisitor.java
@@ -67,7 +67,7 @@ public abstract class MethodVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of the {@code
    *     ASM}<i>x</i> values in {@link Opcodes}.
    */
-  public MethodVisitor(final int api) {
+  protected MethodVisitor(final int api) {
     this(api, null);
   }
 
@@ -79,7 +79,7 @@ public abstract class MethodVisitor {
    * @param methodVisitor the method visitor to which this visitor must delegate method calls. May
    *     be null.
    */
-  public MethodVisitor(final int api, final MethodVisitor methodVisitor) {
+  protected MethodVisitor(final int api, final MethodVisitor methodVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
         && api != Opcodes.ASM7
@@ -349,12 +349,12 @@ public abstract class MethodVisitor {
    *
    * @param opcode the opcode of the local variable instruction to be visited. This opcode is either
    *     ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE or RET.
-   * @param var the operand of the instruction to be visited. This operand is the index of a local
-   *     variable.
+   * @param varIndex the operand of the instruction to be visited. This operand is the index of a
+   *     local variable.
    */
-  public void visitVarInsn(final int opcode, final int var) {
+  public void visitVarInsn(final int opcode, final int varIndex) {
     if (mv != null) {
-      mv.visitVarInsn(opcode, var);
+      mv.visitVarInsn(opcode, varIndex);
     }
   }
 
diff --git a/spring-core/src/main/java/org/springframework/asm/MethodWriter.java b/spring-core/src/main/java/org/springframework/asm/MethodWriter.java
index 54f9b1c4a5d..58fa599721f 100644
--- a/spring-core/src/main/java/org/springframework/asm/MethodWriter.java
+++ b/spring-core/src/main/java/org/springframework/asm/MethodWriter.java
@@ -466,7 +466,8 @@ final class MethodWriter extends MethodVisitor {
 
   /**
    * Indicates what must be computed. Must be one of {@link #COMPUTE_ALL_FRAMES}, {@link
-   * #COMPUTE_INSERTED_FRAMES}, {@link #COMPUTE_MAX_STACK_AND_LOCAL} or {@link #COMPUTE_NOTHING}.
+   * #COMPUTE_INSERTED_FRAMES}, {@link COMPUTE_MAX_STACK_AND_LOCAL_FROM_FRAMES}, {@link
+   * #COMPUTE_MAX_STACK_AND_LOCAL} or {@link #COMPUTE_NOTHING}.
    */
   private final int compute;
 
@@ -904,26 +905,26 @@ final class MethodWriter extends MethodVisitor {
   }
 
   @Override
-  public void visitVarInsn(final int opcode, final int var) {
+  public void visitVarInsn(final int opcode, final int varIndex) {
     lastBytecodeOffset = code.length;
     // Add the instruction to the bytecode of the method.
-    if (var < 4 && opcode != Opcodes.RET) {
+    if (varIndex < 4 && opcode != Opcodes.RET) {
       int optimizedOpcode;
       if (opcode < Opcodes.ISTORE) {
-        optimizedOpcode = Constants.ILOAD_0 + ((opcode - Opcodes.ILOAD) << 2) + var;
+        optimizedOpcode = Constants.ILOAD_0 + ((opcode - Opcodes.ILOAD) << 2) + varIndex;
       } else {
-        optimizedOpcode = Constants.ISTORE_0 + ((opcode - Opcodes.ISTORE) << 2) + var;
+        optimizedOpcode = Constants.ISTORE_0 + ((opcode - Opcodes.ISTORE) << 2) + varIndex;
       }
       code.putByte(optimizedOpcode);
-    } else if (var >= 256) {
-      code.putByte(Constants.WIDE).put12(opcode, var);
+    } else if (varIndex >= 256) {
+      code.putByte(Constants.WIDE).put12(opcode, varIndex);
     } else {
-      code.put11(opcode, var);
+      code.put11(opcode, varIndex);
     }
     // If needed, update the maximum stack size and number of locals, and stack map frames.
     if (currentBasicBlock != null) {
       if (compute == COMPUTE_ALL_FRAMES || compute == COMPUTE_INSERTED_FRAMES) {
-        currentBasicBlock.frame.execute(opcode, var, null, null);
+        currentBasicBlock.frame.execute(opcode, varIndex, null, null);
       } else {
         if (opcode == Opcodes.RET) {
           // No stack size delta.
@@ -945,9 +946,9 @@ final class MethodWriter extends MethodVisitor {
           || opcode == Opcodes.DLOAD
           || opcode == Opcodes.LSTORE
           || opcode == Opcodes.DSTORE) {
-        currentMaxLocals = var + 2;
+        currentMaxLocals = varIndex + 2;
       } else {
-        currentMaxLocals = var + 1;
+        currentMaxLocals = varIndex + 1;
       }
       if (currentMaxLocals > maxLocals) {
         maxLocals = currentMaxLocals;
@@ -1307,21 +1308,21 @@ final class MethodWriter extends MethodVisitor {
   }
 
   @Override
-  public void visitIincInsn(final int var, final int increment) {
+  public void visitIincInsn(final int varIndex, final int increment) {
     lastBytecodeOffset = code.length;
     // Add the instruction to the bytecode of the method.
-    if ((var > 255) || (increment > 127) || (increment < -128)) {
-      code.putByte(Constants.WIDE).put12(Opcodes.IINC, var).putShort(increment);
+    if ((varIndex > 255) || (increment > 127) || (increment < -128)) {
+      code.putByte(Constants.WIDE).put12(Opcodes.IINC, varIndex).putShort(increment);
     } else {
-      code.putByte(Opcodes.IINC).put11(var, increment);
+      code.putByte(Opcodes.IINC).put11(varIndex, increment);
     }
     // If needed, update the maximum stack size and number of locals, and stack map frames.
     if (currentBasicBlock != null
         && (compute == COMPUTE_ALL_FRAMES || compute == COMPUTE_INSERTED_FRAMES)) {
-      currentBasicBlock.frame.execute(Opcodes.IINC, var, null, null);
+      currentBasicBlock.frame.execute(Opcodes.IINC, varIndex, null, null);
     }
     if (compute != COMPUTE_NOTHING) {
-      int currentMaxLocals = var + 1;
+      int currentMaxLocals = varIndex + 1;
       if (currentMaxLocals > maxLocals) {
         maxLocals = currentMaxLocals;
       }
diff --git a/spring-core/src/main/java/org/springframework/asm/ModuleVisitor.java b/spring-core/src/main/java/org/springframework/asm/ModuleVisitor.java
index bd2e9445b22..276035481bc 100644
--- a/spring-core/src/main/java/org/springframework/asm/ModuleVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/ModuleVisitor.java
@@ -53,7 +53,7 @@ public abstract class ModuleVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM6}
    *     or {@link Opcodes#ASM7}.
    */
-  public ModuleVisitor(final int api) {
+  protected ModuleVisitor(final int api) {
     this(api, null);
   }
 
@@ -65,7 +65,7 @@ public abstract class ModuleVisitor {
    * @param moduleVisitor the module visitor to which this visitor must delegate method calls. May
    *     be null.
    */
-  public ModuleVisitor(final int api, final ModuleVisitor moduleVisitor) {
+  protected ModuleVisitor(final int api, final ModuleVisitor moduleVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
         && api != Opcodes.ASM7
diff --git a/spring-core/src/main/java/org/springframework/asm/RecordComponentVisitor.java b/spring-core/src/main/java/org/springframework/asm/RecordComponentVisitor.java
index a66043c4d11..6e767b6e707 100644
--- a/spring-core/src/main/java/org/springframework/asm/RecordComponentVisitor.java
+++ b/spring-core/src/main/java/org/springframework/asm/RecordComponentVisitor.java
@@ -53,7 +53,7 @@ public abstract class RecordComponentVisitor {
    * @param api the ASM API version implemented by this visitor. Must be one of {@link Opcodes#ASM8}
    *     or {@link Opcodes#ASM9}.
    */
-  public RecordComponentVisitor(final int api) {
+  protected RecordComponentVisitor(final int api) {
     this(api, null);
   }
 
@@ -64,7 +64,7 @@ public abstract class RecordComponentVisitor {
    * @param recordComponentVisitor the record component visitor to which this visitor must delegate
    *     method calls. May be null.
    */
-  public RecordComponentVisitor(
+  protected RecordComponentVisitor(
       final int api, final RecordComponentVisitor recordComponentVisitor) {
     if (api != Opcodes.ASM9
         && api != Opcodes.ASM8
diff --git a/spring-core/src/main/java/org/springframework/asm/Type.java b/spring-core/src/main/java/org/springframework/asm/Type.java
index 5850ffdeb69..f346c6a44b6 100644
--- a/spring-core/src/main/java/org/springframework/asm/Type.java
+++ b/spring-core/src/main/java/org/springframework/asm/Type.java
@@ -440,7 +440,7 @@ public final class Type {
       case '(':
         return new Type(METHOD, descriptorBuffer, descriptorBegin, descriptorEnd);
       default:
-        throw new IllegalArgumentException();
+        throw new IllegalArgumentException("Invalid descriptor: " + descriptorBuffer);
     }
   }