Don't store allocator

The plan is to implement a separate "verify" function that is separate
from parsing or formatting.

flake.nix

@@ -19,6 +19,8 @@
           zls
           javaPackages.compiler.openjdk25
           jdt-language-server
+          kotlin
+          kotlin-language-server
         ];
 
         buildInputs = with pkgs; [];

src/Class.zig

@@ -4,14 +4,13 @@ const EnumFlags = @import("EnumFlags.zig").EnumFlags;
 
 pub const FieldInfo = @import("Class/FieldInfo.zig");
 pub const MethodInfo = @import("Class/MethodInfo.zig");
-pub const AttributeInfo = @import("Class/AttributeInfo.zig");
-
-allocator: std.mem.Allocator,
+pub const AttributeInfo = @import("Class/AttributeInfo.zig").AttributeInfo;
+pub const ConstantPool = @import("Class/ConstantPool.zig");
 
 magic: u32,
 minor_version: u16,
 major_version: u16,
-constant_pool: []?ConstantPoolInfo,
+constant_pool: ConstantPool,
 access_flags: ClassAccessFlags,
 this_class: u16,
 super_class: u16,
@@ -22,7 +21,7 @@ attributes: []AttributeInfo,
 
 const Self = @This();
 
-pub const ClassFlags = enum(u16) {
+pub const ClassAccessFlags = EnumFlags(enum(u16) {
     public = 0x0001,
     final = 0x0010,
     super = 0x0020,
@@ -31,9 +30,8 @@ pub const ClassFlags = enum(u16) {
     synthetic = 0x1000,
     annotation = 0x2000,
     @"enum" = 0x4000,
-};
-
-pub const ClassAccessFlags = EnumFlags(ClassFlags);
+    module = 0x8000,
+});
 
 pub const ParseError = std.Io.Reader.Error || std.mem.Allocator.Error || error {
     InvalidMagicNumber,
@@ -45,7 +43,7 @@ pub const ResolveError = error {
     InvalidConstantType,
 };
 
-pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Self {
+pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) (ParseError || ResolveError)!Self {
     const magic = try input.takeInt(u32, .big);
     if (magic != 0xCAFEBABE) {
         return ParseError.InvalidMagicNumber;
@@ -54,15 +52,10 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
     const minor_version = try input.takeInt(u16, .big);
     const major_version = try input.takeInt(u16, .big);
 
-    const constant_pool = try parseConstantPool(input, allocator);
-    errdefer {
-        for (constant_pool) |*cp_info| {
-            if (cp_info.*) |*c| c.deinit(allocator);
-        }
-        allocator.free(constant_pool);
-    }
+    var constant_pool: ConstantPool = try .parse(input, allocator);
+    errdefer constant_pool.deinit(allocator);
 
-    const access_flags: ClassAccessFlags = .{ .mask = try input.takeInt(u16, .big) };
+    const access_flags: ClassAccessFlags = .from(try input.takeInt(u16, .big));
 
     const this_class = try input.takeInt(u16, .big);
     const super_class = try input.takeInt(u16, .big);
@@ -70,7 +63,7 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
     const interfaces = try parseInterfaces(input, allocator);
     errdefer allocator.free(interfaces);
 
-    const fields = try parseFields(input, allocator);
+    const fields = try parseFields(input, constant_pool, allocator);
     errdefer {
         for (fields) |*field| {
             field.deinit(allocator);
@@ -78,7 +71,7 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
         allocator.free(fields);
     }
 
-    const methods = try parseMethods(input, allocator);
+    const methods = try parseMethods(input, constant_pool, allocator);
     errdefer {
         for (methods) |*method| {
             method.deinit(allocator);
@@ -86,7 +79,7 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
         allocator.free(methods);
     }
 
-    const attributes = try parseAttributes(input, allocator);
+    const attributes = try parseAttributes(input, constant_pool, allocator);
     errdefer {
         for (attributes) |*attribute| {
             attribute.deinit(allocator);
@@ -95,7 +88,6 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
     }
 
     return .{
-        .allocator = allocator,
         .magic = magic,
         .minor_version = minor_version,
         .major_version = major_version,
@@ -110,30 +102,6 @@ pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Sel
     };
 }
 
-fn parseConstantPool(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError![]?ConstantPoolInfo {
-    const constant_pool_size = try input.takeInt(u16, .big);
-    const constant_pool = try allocator.alloc(?ConstantPoolInfo, constant_pool_size - 1);
-    errdefer allocator.free(constant_pool);
-
-    var i: usize = 0;
-    while (i < constant_pool_size - 1) {
-        defer i += 1;
-
-        const cp_info = try ConstantPoolInfo.parse(input, allocator);
-        constant_pool[i] = cp_info;
-
-        switch (cp_info) {
-            .long, .double => {
-                i += 1;
-                constant_pool[i] = null;
-            },
-            else => {},
-        }
-    }
-
-    return constant_pool;
-}
-
 fn parseInterfaces(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError![]u16 {
     const interfaces_count = try input.takeInt(u16, .big);
     const interfaces = try allocator.alloc(u16, interfaces_count);
@@ -146,80 +114,73 @@ fn parseInterfaces(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseErr
     return interfaces;
 }
 
-fn parseFields(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError![]FieldInfo {
+fn parseFields(input: *std.Io.Reader, constant_pool: ConstantPool, allocator: std.mem.Allocator) (ParseError || ResolveError)![]FieldInfo {
     const fields_count = try input.takeInt(u16, .big);
     const fields = try allocator.alloc(FieldInfo, fields_count);
     errdefer allocator.free(fields);
 
     for (0..fields_count) |i| {
-        fields[i] = try FieldInfo.parse(input, allocator);
+        fields[i] = try FieldInfo.parse(input, constant_pool, allocator);
     }
 
     return fields;
 }
 
-fn parseMethods(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError![]MethodInfo {
+fn parseMethods(input: *std.Io.Reader, constant_pool: ConstantPool, allocator: std.mem.Allocator) (ParseError || ResolveError)![]MethodInfo {
     const methods_count = try input.takeInt(u16, .big);
     const methods = try allocator.alloc(MethodInfo, methods_count);
     errdefer allocator.free(methods);
 
     for (0..methods_count) |i| {
-        methods[i] = try MethodInfo.parse(input, allocator);
+        methods[i] = try .parse(input, constant_pool, allocator);
     }
 
     return methods;
 }
 
-pub fn parseAttributes(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError![]AttributeInfo {
+pub fn parseAttributes(input: *std.Io.Reader, constant_pool: ConstantPool, allocator: std.mem.Allocator) (ParseError || ResolveError)![]AttributeInfo {
     const attributes_count = try input.takeInt(u16, .big);
     const attributes = try allocator.alloc(AttributeInfo, attributes_count);
     errdefer allocator.free(attributes);
 
     for (0..attributes_count) |i| {
-        attributes[i] = try AttributeInfo.parse(input, allocator);
+        attributes[i] = try AttributeInfo.parse(input, constant_pool, allocator);
     }
 
     return attributes;
 }
 
-pub fn deinit(self: *Self) void {
-    self.freeConstantPool();
-    self.freeInterfaces();
-    self.freeFields();
-    self.freeMethods();
-    self.freeAttributes();
+pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
+    self.constant_pool.deinit(allocator);
+    self.freeInterfaces(allocator);
+    self.freeFields(allocator);
+    self.freeMethods(allocator);
+    self.freeAttributes(allocator);
 }
 
-fn freeConstantPool(self: *Self) void {
-    for (self.constant_pool) |*cp_info| {
-        if (cp_info.*) |*c| c.deinit(self.allocator);
-    }
-    self.allocator.free(self.constant_pool);
+fn freeInterfaces(self: *Self, allocator: std.mem.Allocator) void {
+    allocator.free(self.interfaces);
 }
 
-fn freeInterfaces(self: *Self) void {
-    self.allocator.free(self.interfaces);
-}
-
-fn freeFields(self: *Self) void {
+fn freeFields(self: *Self, allocator: std.mem.Allocator) void {
     for (self.fields) |*field_info| {
-        field_info.deinit(self.allocator);
+        field_info.deinit(allocator);
     }
-    self.allocator.free(self.fields);
+    allocator.free(self.fields);
 }
 
-fn freeMethods(self: *Self) void {
+fn freeMethods(self: *Self, allocator: std.mem.Allocator) void {
     for (self.methods) |*method_info| {
-        method_info.deinit(self.allocator);
+        method_info.deinit(allocator);
     }
-    self.allocator.free(self.methods);
+    allocator.free(self.methods);
 }
 
-fn freeAttributes(self: *Self) void {
+fn freeAttributes(self: *Self, allocator: std.mem.Allocator) void {
     for (self.attributes) |*attr| {
-        attr.deinit(self.allocator);
+        attr.deinit(allocator);
     }
-    self.allocator.free(self.attributes);
+    allocator.free(self.attributes);
 }
 
 pub fn jsonStringify(self: *const Self, jws: *std.json.Stringify) !void {
@@ -246,11 +207,11 @@ pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
 
     const this_class = self.thisClass() catch return error.WriteFailed;
     _ = try w.write("this class:\n");
-    try this_class.format(w, depth, indent + 1, self.constant_pool);
+    try this_class.indentedFormat(w, depth, indent + 1, self.constant_pool);
 
     _ = try w.write("super class:\n");
     if (self.superClass() catch return error.WriteFailed) |super_class| {
-        try super_class.format(w, depth, indent + 1, self.constant_pool);
+        try super_class.indentedFormat(w, depth, indent + 1, self.constant_pool);
     }
 
     _ = try w.write("interfaces:\n");
@@ -258,13 +219,11 @@ pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
         indent += 1;
         defer indent -= 1;
 
-        if (interface >= self.constant_pool.len) return error.WriteFailed;
-        const cp_info = self.constant_pool[interface - 1];
-        if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .class) return error.WriteFailed;
+        const info = self.constant_pool.getTag(interface, .class) catch return error.WriteFailed;
 
         try w.splatByteAll(' ', depth * indent);
         try w.print("{d}:\n", .{ i });
-        try cp_info.?.format(w, depth, indent + 1, self.constant_pool);
+        try info.indentedFormat(w, depth, indent + 1, self.constant_pool);
     }
 
     _ = try w.write("fields:\n");
@@ -274,7 +233,7 @@ pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
 
         try w.splatByteAll(' ', depth * indent);
         try w.print("{d}:\n", .{ i });
-        try field.format(w, depth, indent + 1, self.allocator, self.constant_pool);
+        try field.indentedFormat(w, depth, indent + 1, self.constant_pool);
     }
 
     _ = try w.write("methods:\n");
@@ -284,7 +243,7 @@ pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
 
         try w.splatByteAll(' ', depth * indent);
         try w.print("{d}:\n", .{ i });
-        try method.format(w, depth, indent + 1, self.allocator, self.constant_pool);
+        try method.indentedFormat(w, depth, indent + 1, self.constant_pool);
     }
 
     _ = try w.write("attributes:\n");
@@ -294,476 +253,15 @@ pub fn format(self: *const Self, w: *std.Io.Writer) std.Io.Writer.Error!void {
 
         try w.splatByteAll(' ', depth * indent);
         try w.print("{d}:\n", .{ i });
-        try attribute.format(w, depth, indent + 1, self.allocator, self.constant_pool);
+        try attribute.indentedFormat(w, depth, indent + 1, self.constant_pool);
     }
 }
 
-pub fn thisClass(self: *const Self) ResolveError!ConstantPoolInfo {
-    const this_class = self.this_class - 1;
-    if (this_class >= self.constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-    const cp_info = self.constant_pool[this_class];
-    if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .class) return ResolveError.InvalidConstantType;
-    return cp_info.?;
+pub fn thisClass(self: *const Self) ResolveError!ConstantPool.Info {
+    return self.constant_pool.getTag(self.this_class, .class);
 }
 
-pub fn superClass(self: *const Self) ResolveError!?ConstantPoolInfo {
-    if (self.super_class == 0) {
-        const this_class = (try self.thisClass()).class;
-        const this_class_name = (try this_class.name(self.constant_pool)).utf8;
-        if (!std.mem.eql(u8, this_class_name.bytes, "java/lang/Object")) return ResolveError.InvalidConstantType;
-        return null;
-    } else {
-        const super_class = self.super_class - 1;
-        if (super_class >= self.constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-        const cp_info = self.constant_pool[super_class];
-        if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .class) return ResolveError.InvalidConstantType;
-
-        if (self.access_flags.contains(.interface)) {
-            const super_class_name = (try cp_info.?.class.name(self.constant_pool)).utf8;
-            if (!std.mem.eql(u8, super_class_name.bytes, "java/lang/Object")) return ResolveError.InvalidConstantType;
-        } else {
-            // TODO: Assert that superclass does not have ACC_FINAL flag set.
-        }
-        return cp_info.?;
-    }
+pub fn superClass(self: *const Self) ResolveError!?ConstantPool.Info {
+    return self.constant_pool.getTagOptional(self.super_class, .class);
 }
 
-pub const ConstantPoolInfo = union(ConstantPoolInfo.Tag) {
-    class: Class,
-    field_ref: FieldRef,
-    method_ref: MethodRef,
-    interface_method_ref: InterfaceMethodRef,
-    string: String,
-    integer: Integer,
-    float: Float,
-    long: Long,
-    double: Double,
-    name_and_type: NameAndType,
-    utf8: Utf8,
-    method_handle: MethodHandle,
-    method_type: MethodType,
-    invoke_dynamic: InvokeDynamic,
-
-    pub const Tag = enum(u8) {
-        class = 7,
-        field_ref = 9,
-        method_ref = 10,
-        interface_method_ref = 11,
-        string = 8,
-        integer = 3,
-        float = 4,
-        long = 5,
-        double = 6,
-        name_and_type = 12,
-        utf8 = 1,
-        method_handle = 15,
-        method_type = 16,
-        invoke_dynamic = 18,
-    };
-
-    pub const Class = struct {
-        name_index: u16,
-
-        pub fn name(self: *const Class, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_index = self.name_index - 1;
-            if (name_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const FieldRef = struct {
-        class_index: u16,
-        name_and_type_index: u16,
-
-        pub fn class(self: *const FieldRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const class_index = self.class_index - 1;
-            if (class_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[class_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .class) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-
-        pub fn nameAndType(self: *const FieldRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_and_type_index = self.name_and_type_index - 1;
-            if (name_and_type_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_and_type_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .name_and_type) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const MethodRef = struct {
-        class_index: u16,
-        name_and_type_index: u16,
-
-        pub fn class(self: *const MethodRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const class_index = self.class_index - 1;
-            if (class_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[class_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .class) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-
-        pub fn nameAndType(self: *const MethodRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_and_type_index = self.name_and_type_index - 1;
-            if (name_and_type_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_and_type_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .name_and_type) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const InterfaceMethodRef = struct {
-        class_index: u16,
-        name_and_type_index: u16,
-
-        pub fn class(self: *const InterfaceMethodRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const class_index = self.class_index - 1;
-            if (class_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[class_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .class) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-
-        pub fn nameAndType(self: *const InterfaceMethodRef, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_and_type_index = self.name_and_type_index - 1;
-            if (name_and_type_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_and_type_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .name_and_type) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const String = struct {
-        string_index: u16,
-
-        pub fn string(self: *const String, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const string_index = self.string_index - 1;
-            if (string_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[string_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const Integer = struct {
-        bytes: u32,
-    };
-
-    pub const Float = struct {
-        bytes: u32,
-    };
-
-    pub const Long = struct {
-        high_bytes: u32,
-        low_bytes: u32,
-    };
-
-    pub const Double = struct {
-        high_bytes: u32,
-        low_bytes: u32,
-    };
-
-    pub const NameAndType = struct {
-        name_index: u16,
-        descriptor_index: u16,
-
-        pub fn name(self: *const NameAndType, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_index = self.name_index - 1;
-            if (name_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-
-        pub fn descriptor(self: *const NameAndType, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const descriptor_index = self.descriptor_index - 1;
-            if (descriptor_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[descriptor_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const Utf8 = struct {
-        bytes: []const u8,
-    };
-
-    pub const MethodHandle = struct {
-        reference_kind: Kind,
-        reference_index: u16,
-
-        pub const Kind = enum(u8) {
-            get_field = 1,
-            get_static = 2,
-            put_field = 3,
-            put_static = 4,
-            invoke_virtual = 5,
-            invoke_static = 6,
-            invoke_special = 7,
-            new_invoke_special = 8,
-            invoke_interface = 9,
-        };
-
-        pub fn reference(self: *const MethodHandle, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const reference_index = self.reference_index - 1;
-            if (reference_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[reference_index];
-            return switch (self.reference_kind) {
-                .get_field, .get_static, .put_field, .put_static => blk: {
-                    if (cp_info == null or @as(Tag, cp_info.?) != .field_ref) break :blk ResolveError.InvalidConstantType;
-                    break :blk cp_info.?;
-                },
-                .invoke_virtual, .invoke_static, .invoke_special, .new_invoke_special => blk: {
-                    if (cp_info == null or @as(Tag, cp_info.?) != .method_ref) break :blk ResolveError.InvalidConstantType;
-                    break :blk cp_info.?;
-                },
-                .invoke_interface => blk: {
-                    if (cp_info == null or @as(Tag, cp_info.?) != .interface_method_ref) break :blk ResolveError.InvalidConstantType;
-                    break :blk cp_info.?;
-                },
-            };
-        }
-    };
-
-    pub const MethodType = struct {
-        descriptor_index: u16,
-
-        pub fn descriptor(self: *const MethodType, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const descriptor_index = self.descriptor_index - 1;
-            if (descriptor_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[descriptor_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub const InvokeDynamic = struct {
-        bootstrap_method_attr_index: u16,
-        name_and_type_index: u16,
-
-        pub fn nameAndType(self: *const InvokeDynamic, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-            const name_and_type_index = self.name_and_type_index - 1;
-            if (name_and_type_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-            const cp_info = constant_pool[name_and_type_index];
-            if (cp_info == null or @as(Tag, cp_info.?) != .name_and_type) return ResolveError.InvalidConstantType;
-            return cp_info.?;
-        }
-    };
-
-    pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!ConstantPoolInfo {
-        const tag_byte = try input.takeByte();
-        const tag = std.enums.fromInt(Tag, tag_byte) orelse return ParseError.InvalidTag;
-
-        return switch (tag) {
-            .class => .{
-                .class = .{
-                    .name_index = try input.takeInt(u16, .big),
-                },
-            },
-            .field_ref => .{
-                .field_ref = .{
-                    .class_index = try input.takeInt(u16, .big),
-                    .name_and_type_index = try input.takeInt(u16, .big),
-                },
-            },
-            .method_ref => .{
-                .method_ref = .{
-                    .class_index = try input.takeInt(u16, .big),
-                    .name_and_type_index = try input.takeInt(u16, .big),
-                },
-            },
-            .interface_method_ref => .{
-                .interface_method_ref = .{
-                    .class_index = try input.takeInt(u16, .big),
-                    .name_and_type_index = try input.takeInt(u16, .big),
-                },
-            },
-            .string => .{
-                .string = .{
-                    .string_index = try input.takeInt(u16, .big),
-                },
-            },
-            .integer => .{
-                .integer = .{
-                    .bytes = try input.takeInt(u32, .big),
-                },
-            },
-            .float => .{
-                .integer = .{
-                    .bytes = try input.takeInt(u32, .big),
-                },
-            },
-            .long => .{
-                .long = .{
-                    .high_bytes = try input.takeInt(u32, .big),
-                    .low_bytes = try input.takeInt(u32, .big),
-                },
-            },
-            .double => .{
-                .double = .{
-                    .high_bytes = try input.takeInt(u32, .big),
-                    .low_bytes = try input.takeInt(u32, .big),
-                },
-            },
-            .name_and_type => .{
-                .name_and_type = .{
-                    .name_index = try input.takeInt(u16, .big),
-                    .descriptor_index = try input.takeInt(u16, .big),
-                },
-            },
-            .utf8 => blk: {
-                const length = try input.takeInt(u16, .big);
-                const bytes = try input.readAlloc(allocator, length);
-
-                break :blk .{
-                    .utf8 = .{
-                        .bytes = bytes,
-                    },
-                };
-            },
-            .method_handle => blk: {
-                const kind_byte = try input.takeByte();
-                const kind = std.enums.fromInt(MethodHandle.Kind, kind_byte) orelse return ParseError.InvalidTag;
-
-                break :blk .{
-                    .method_handle = .{
-                        .reference_kind = kind,
-                        .reference_index = try input.takeInt(u16, .big),
-                    },
-                };
-            },
-            .method_type => .{
-                .method_type = .{
-                    .descriptor_index = try input.takeInt(u16, .big),
-                },
-            },
-            .invoke_dynamic => .{
-                .invoke_dynamic = .{
-                    .bootstrap_method_attr_index = try input.takeInt(u16, .big),
-                    .name_and_type_index = try input.takeInt(u16, .big),
-                },
-            },
-        };
-    }
-
-    pub fn deinit(self: *ConstantPoolInfo, allocator: std.mem.Allocator) void {
-        switch (self.*) {
-            .utf8 => |info| allocator.free(info.bytes),
-            else => {},
-        }
-    }
-
-    pub fn format(self: *const ConstantPoolInfo, w: *std.Io.Writer, depth: usize, indent: u8, constant_pool: []const ?ConstantPoolInfo) std.Io.Writer.Error!void {
-        try w.splatByteAll(' ', depth * indent);
-        try w.print("constant_value_type: {s}\n", .{ @tagName(self.*) });
-
-        switch (self.*) {
-            .class => |class| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name:\n");
-                const class_name = class.name(constant_pool) catch return error.WriteFailed;
-                try class_name.format(w, depth, indent + 1, constant_pool);
-            },
-            .field_ref => |field_ref| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("class:\n");
-                const class = field_ref.class(constant_pool) catch return error.WriteFailed;
-                try class.format(w, depth, indent + 1, constant_pool);
-
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name_and_type:\n");
-                const name_and_type = field_ref.nameAndType(constant_pool) catch return error.WriteFailed;
-                try name_and_type.format(w, depth, indent + 1, constant_pool);
-            },
-            .method_ref => |method_ref| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("class:\n");
-                const class = method_ref.class(constant_pool) catch return error.WriteFailed;
-                try class.format(w, depth, indent + 1, constant_pool);
-
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name_and_type:\n");
-                const name_and_type = method_ref.nameAndType(constant_pool) catch return error.WriteFailed;
-                try name_and_type.format(w, depth, indent + 1, constant_pool);
-            },
-            .interface_method_ref => |interface_method_ref| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("class:\n");
-                const class = interface_method_ref.class(constant_pool) catch return error.WriteFailed;
-                try class.format(w, depth, indent + 1, constant_pool);
-
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name_and_type:\n");
-                const name_and_type = interface_method_ref.nameAndType(constant_pool) catch return error.WriteFailed;
-                try name_and_type.format(w, depth, indent + 1, constant_pool);
-            },
-            .string => |string| {
-                const s = string.string(constant_pool) catch return error.WriteFailed;
-                try s.format(w, depth, indent + 1, constant_pool);
-            },
-            .integer => |integer| {
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("integer: {d}\n", .{ integer.bytes });
-            },
-            .float => |float| {
-                const f: f32 = @bitCast(float.bytes);
-
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("float: {d}\n", .{ f });
-            },
-            .long => |long| {
-                const l: u64 = (@as(u64, long.high_bytes) << 32) | long.low_bytes;
-
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("long: {d}\n", .{ l });
-            },
-            .double => |double| {
-                const l: u64 = (@as(u64, double.high_bytes) << 32) | double.low_bytes;
-                const d: f64 = @bitCast(l);
-
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("double: {d}\n", .{ d });
-            },
-            .name_and_type => |name_and_type| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name:\n");
-                const name = name_and_type.name(constant_pool) catch return error.WriteFailed;
-                try name.format(w, depth, indent + 1, constant_pool);
-
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("descriptor:\n");
-                const descriptor = name_and_type.descriptor(constant_pool) catch return error.WriteFailed;
-                try descriptor.format(w, depth, indent + 1, constant_pool);
-            },
-            .utf8 => |utf8| {
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("bytes: \"{s}\"\n", .{ utf8.bytes });
-            },
-            .method_handle => |method_handle| {
-                try w.splatByteAll(' ', depth * indent);
-                try w.print("kind: {t}\n", .{ method_handle.reference_kind });
-
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("reference:\n");
-                const reference = method_handle.reference(constant_pool) catch return error.WriteFailed;
-                try reference.format(w, depth, indent + 1, constant_pool);
-            },
-            .method_type => |method_type| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("descriptor:\n");
-                const descriptor = method_type.descriptor(constant_pool) catch return error.WriteFailed;
-                try descriptor.format(w, depth, indent + 1, constant_pool);
-            },
-            .invoke_dynamic => |invoke_dynamic| {
-                try w.splatByteAll(' ', depth * indent);
-                _ = try w.write("name_and_type:\n");
-                const name_and_type = invoke_dynamic.nameAndType(constant_pool) catch return error.WriteFailed;
-                try name_and_type.format(w, depth, indent + 1, constant_pool);
-            },
-        }
-    }
-};
-

src/Class/ConstantPool.zig

@@ -0,0 +1,547 @@
+const std = @import("std");
+
+const Class = @import("../Class.zig");
+const AttributeInfo = Class.AttributeInfo;
+const ParseError = Class.ParseError;
+const ResolveError = Class.ResolveError;
+
+constant_pool: []?Info,
+
+const Self = @This();
+
+pub const Info = union(Info.Tag) {
+    class: Info.Class,
+    field_ref: FieldRef,
+    method_ref: MethodRef,
+    interface_method_ref: InterfaceMethodRef,
+    string: String,
+    integer: Integer,
+    float: Float,
+    long: Long,
+    double: Double,
+    name_and_type: NameAndType,
+    utf8: Utf8,
+    method_handle: MethodHandle,
+    method_type: MethodType,
+    dynamic: Dynamic,
+    invoke_dynamic: InvokeDynamic,
+    module: Module,
+    package: Package,
+
+    pub const Tag = enum(u8) {
+        class = 7,
+        field_ref = 9,
+        method_ref = 10,
+        interface_method_ref = 11,
+        string = 8,
+        integer = 3,
+        float = 4,
+        long = 5,
+        double = 6,
+        name_and_type = 12,
+        utf8 = 1,
+        method_handle = 15,
+        method_type = 16,
+        dynamic = 17,
+        invoke_dynamic = 18,
+        module = 19,
+        package = 20,
+
+        pub fn loadable(self: Tag) bool {
+            return switch (self) {
+                .integer, .float, .long, .double, .class, .string, .method_handle, .method_type, .dynamic => true,
+                else => false,
+            };
+        }
+    };
+
+    pub const Class = struct {
+        name_index: u16,
+
+        pub fn name(self: *const Info.Class, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_index, .utf8);
+        }
+    };
+
+    pub const FieldRef = struct {
+        class_index: u16,
+        name_and_type_index: u16,
+
+        pub fn class(self: *const FieldRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.class_index, .class);
+        }
+
+        pub fn nameAndType(self: *const FieldRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_and_type_index, .name_and_type);
+        }
+    };
+
+    pub const MethodRef = struct {
+        class_index: u16,
+        name_and_type_index: u16,
+
+        pub fn class(self: *const MethodRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.class_index, .class);
+        }
+
+        pub fn nameAndType(self: *const MethodRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_and_type_index, .name_and_type);
+        }
+    };
+
+    pub const InterfaceMethodRef = struct {
+        class_index: u16,
+        name_and_type_index: u16,
+
+        pub fn class(self: *const InterfaceMethodRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.class_index, .class);
+        }
+
+        pub fn nameAndType(self: *const InterfaceMethodRef, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_and_type_index, .name_and_type);
+        }
+    };
+
+    pub const String = struct {
+        string_index: u16,
+
+        pub fn string(self: *const String, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.string_index, .utf8);
+        }
+    };
+
+    pub const Integer = struct {
+        bytes: u32,
+    };
+
+    pub const Float = struct {
+        bytes: u32,
+
+        pub fn float(self: *const Float) f32 {
+            return @bitCast(self.bytes);
+        }
+    };
+
+    pub const Long = struct {
+        high_bytes: u32,
+        low_bytes: u32,
+
+        pub fn long(self: *const Long) u64 {
+            return (@as(u64, self.high_bytes) << 32) | self.low_bytes;
+        }
+    };
+
+    pub const Double = struct {
+        high_bytes: u32,
+        low_bytes: u32,
+
+        pub fn double(self: *const Double) f64 {
+            return @bitCast((@as(u64, self.high_bytes) << 32) | self.low_bytes);
+        }
+    };
+
+    pub const NameAndType = struct {
+        name_index: u16,
+        descriptor_index: u16,
+
+        pub fn name(self: *const NameAndType, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_index, .utf8);
+        }
+
+        pub fn descriptor(self: *const NameAndType, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.descriptor_index, .utf8);
+        }
+    };
+
+    pub const Utf8 = struct {
+        bytes: []const u8,
+    };
+
+    pub const MethodHandle = struct {
+        reference_kind: Kind,
+        reference_index: u16,
+
+        pub const Kind = enum(u8) {
+            get_field = 1,
+            get_static = 2,
+            put_field = 3,
+            put_static = 4,
+            invoke_virtual = 5,
+            invoke_static = 6,
+            invoke_special = 7,
+            new_invoke_special = 8,
+            invoke_interface = 9,
+        };
+
+        pub fn reference(self: *const MethodHandle, constant_pool: Self) ResolveError!Info {
+            const info = try constant_pool.get(self.reference_index);
+            return switch (self.reference_kind) {
+                .get_field, .get_static, .put_field, .put_static => blk: {
+                    if (!info.is(.field_ref)) break :blk ResolveError.InvalidConstantType;
+                    break :blk info;
+                },
+                .invoke_virtual, .invoke_static, .invoke_special, .new_invoke_special => blk: {
+                    if (!info.is(.method_ref)) break :blk ResolveError.InvalidConstantType;
+                    break :blk info;
+                },
+                .invoke_interface => blk: {
+                    if (!info.is(.interface_method_ref)) break :blk ResolveError.InvalidConstantType;
+                    break :blk info;
+                },
+            };
+        }
+    };
+
+    pub const MethodType = struct {
+        descriptor_index: u16,
+
+        pub fn descriptor(self: *const MethodType, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.descriptor_index, .utf8);
+        }
+    };
+
+    pub const Dynamic = struct {
+        bootstrap_method_attr_index: u16,
+        name_and_type_index: u16,
+
+        pub fn nameAndType(self: *const Dynamic, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_and_type_index, .name_and_type);
+        }
+    };
+
+    pub const InvokeDynamic = struct {
+        bootstrap_method_attr_index: u16,
+        name_and_type_index: u16,
+
+        pub fn nameAndType(self: *const InvokeDynamic, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_and_type_index, .name_and_type);
+        }
+    };
+
+    pub const Module = struct {
+        name_index: u16,
+
+        pub fn name(self: *const Module, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_index, .utf8);
+        }
+    };
+
+    pub const Package = struct {
+        name_index: u16,
+
+        pub fn name(self: *const Package, constant_pool: Self) ResolveError!Info {
+            return constant_pool.getTag(self.name_index, .utf8);
+        }
+    };
+
+    pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Info {
+        const tag_byte = try input.takeByte();
+        const tag = std.enums.fromInt(Tag, tag_byte) orelse return ParseError.InvalidTag;
+
+        return switch (tag) {
+            .class => .{
+                .class = .{
+                    .name_index = try input.takeInt(u16, .big),
+                },
+            },
+            .field_ref => .{
+                .field_ref = .{
+                    .class_index = try input.takeInt(u16, .big),
+                    .name_and_type_index = try input.takeInt(u16, .big),
+                },
+            },
+            .method_ref => .{
+                .method_ref = .{
+                    .class_index = try input.takeInt(u16, .big),
+                    .name_and_type_index = try input.takeInt(u16, .big),
+                },
+            },
+            .interface_method_ref => .{
+                .interface_method_ref = .{
+                    .class_index = try input.takeInt(u16, .big),
+                    .name_and_type_index = try input.takeInt(u16, .big),
+                },
+            },
+            .string => .{
+                .string = .{
+                    .string_index = try input.takeInt(u16, .big),
+                },
+            },
+            .integer => .{
+                .integer = .{
+                    .bytes = try input.takeInt(u32, .big),
+                },
+            },
+            .float => .{
+                .integer = .{
+                    .bytes = try input.takeInt(u32, .big),
+                },
+            },
+            .long => .{
+                .long = .{
+                    .high_bytes = try input.takeInt(u32, .big),
+                    .low_bytes = try input.takeInt(u32, .big),
+                },
+            },
+            .double => .{
+                .double = .{
+                    .high_bytes = try input.takeInt(u32, .big),
+                    .low_bytes = try input.takeInt(u32, .big),
+                },
+            },
+            .name_and_type => .{
+                .name_and_type = .{
+                    .name_index = try input.takeInt(u16, .big),
+                    .descriptor_index = try input.takeInt(u16, .big),
+                },
+            },
+            .utf8 => blk: {
+                const length = try input.takeInt(u16, .big);
+                const bytes = try input.readAlloc(allocator, length);
+
+                break :blk .{
+                    .utf8 = .{
+                        .bytes = bytes,
+                    },
+                };
+            },
+            .method_handle => blk: {
+                const kind_byte = try input.takeByte();
+                const kind = std.enums.fromInt(MethodHandle.Kind, kind_byte) orelse return ParseError.InvalidTag;
+
+                break :blk .{
+                    .method_handle = .{
+                        .reference_kind = kind,
+                        .reference_index = try input.takeInt(u16, .big),
+                    },
+                };
+            },
+            .method_type => .{
+                .method_type = .{
+                    .descriptor_index = try input.takeInt(u16, .big),
+                },
+            },
+            .dynamic => .{
+                .dynamic = .{
+                    .bootstrap_method_attr_index = try input.takeInt(u16, .big),
+                    .name_and_type_index = try input.takeInt(u16, .big),
+                },
+            },
+            .invoke_dynamic => .{
+                .invoke_dynamic = .{
+                    .bootstrap_method_attr_index = try input.takeInt(u16, .big),
+                    .name_and_type_index = try input.takeInt(u16, .big),
+                },
+            },
+            .module => .{
+                .module = .{
+                    .name_index = try input.takeInt(u16, .big),
+                },
+            },
+            .package => .{
+                .package = .{
+                    .name_index = try input.takeInt(u16, .big),
+                },
+            },
+        };
+    }
+
+    pub fn deinit(self: *Info, allocator: std.mem.Allocator) void {
+        switch (self.*) {
+            .utf8 => |info| allocator.free(info.bytes),
+            else => {},
+        }
+    }
+
+    pub fn format(self: *const Info, w: *std.Io.Writer) std.Io.Writer.Error!void {
+        switch (self.*) {
+            .class => |class| try w.print("#{d}", .{ class.name_index }),
+            .field_ref => |field_ref| try w.print("#{d}.#{d}", .{ field_ref.class_index, field_ref.name_and_type_index }),
+            .method_ref => |method_ref| try w.print("#{d}.#{d}", .{ method_ref.class_index, method_ref.name_and_type_index }),
+            .interface_method_ref => |interface_method_ref| try w.print("#{d}.#{d}", .{ interface_method_ref.class_index, interface_method_ref.name_and_type_index }),
+            .string => |string| try w.print("#{d}", .{ string.string_index }),
+            .integer => |integer| try w.print("{d}", .{ integer.bytes }),
+            .float => |float| try w.print("{d}", .{ float.float() }),
+            .long => |long| try w.print("{d}", .{ long.long() }),
+            .double => |double| try w.print("{d}", .{ double.double() }),
+            .name_and_type => |name_and_type| try w.print("#{d}:#{d}", .{ name_and_type.name_index, name_and_type.descriptor_index }),
+            .utf8 => |utf8|  try w.print("\"{s}\"", .{ utf8.bytes }),
+            .method_handle => |method_handle| try w.print("{t} #{d}", .{ method_handle.reference_kind, method_handle.reference_index }),
+            .method_type => |method_type| try w.print("#{d}", .{ method_type.descriptor_index }),
+            .dynamic => |dynamic| try w.print("#{d} #{d}", .{ dynamic.bootstrap_method_attr_index, dynamic.name_and_type_index }),
+            .invoke_dynamic => |invoke_dynamic| try w.print("#{d} #{d}", .{ invoke_dynamic.bootstrap_method_attr_index, invoke_dynamic.name_and_type_index }),
+            .module => |module| try w.print("#{d}", .{ module.name_index }),
+            .package => |package| try w.print("#{d}", .{ package.name_index }),
+        }
+    }
+
+    pub fn indentedFormat(
+        self: *const Info,
+        w: *std.Io.Writer,
+        depth: usize,
+        indent: u8,
+        constant_pool: Self,
+    ) std.Io.Writer.Error!void {
+        try w.splatByteAll(' ', depth * indent);
+        try w.print("constant_value_type: {t}\n", .{ self.* });
+
+        switch (self.*) {
+            .class => |*class| {
+                try formatInfo(w, depth, indent, "name", class, .name, constant_pool);
+            },
+            .field_ref => |*field_ref| {
+                try formatInfo(w, depth, indent, "class", field_ref, .class, constant_pool);
+
+                try formatInfo(w, depth, indent, "name_and_type", field_ref, .nameAndType, constant_pool);
+            },
+            .method_ref => |*method_ref| {
+                try formatInfo(w, depth, indent, "class", method_ref, .class, constant_pool);
+
+                try formatInfo(w, depth, indent, "name_and_type", method_ref, .nameAndType, constant_pool);
+            },
+            .interface_method_ref => |*interface_method_ref| {
+                try formatInfo(w, depth, indent, "class", interface_method_ref, .class, constant_pool);
+
+                try formatInfo(w, depth, indent, "name_and_type", interface_method_ref, .nameAndType, constant_pool);
+            },
+            .string => |*string| {
+                try formatInfo(w, depth, indent, "string", string, .string, constant_pool);
+            },
+            .integer => |*integer| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("integer: {d}\n", .{ integer.bytes });
+            },
+            .float => |*float| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("float: {d}\n", .{ float.float() });
+            },
+            .long => |*long| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("long: {d}\n", .{ long.long() });
+            },
+            .double => |*double| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("double: {d}\n", .{ double.double() });
+            },
+            .name_and_type => |*name_and_type| {
+                try formatInfo(w, depth, indent, "name", name_and_type, .name, constant_pool);
+
+                try formatInfo(w, depth, indent, "descriptor", name_and_type, .descriptor, constant_pool);
+            },
+            .utf8 => |*utf8| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("bytes: \"{s}\"\n", .{ utf8.bytes });
+            },
+            .method_handle => |*method_handle| {
+                try w.splatByteAll(' ', depth * indent);
+                try w.print("kind: {t}\n", .{ method_handle.reference_kind });
+
+                try formatInfo(w, depth, indent, "descriptor", method_handle, .reference, constant_pool);
+            },
+            .method_type => |*method_type| {
+                try formatInfo(w, depth, indent, "descriptor", method_type, .descriptor, constant_pool);
+            },
+            .dynamic => |*dynamic| {
+                try formatInfo(w, depth, indent, "name_and_type", dynamic, .nameAndType, constant_pool);
+            },
+            .invoke_dynamic => |*invoke_dynamic| {
+                try formatInfo(w, depth, indent, "name_and_type", invoke_dynamic, .nameAndType, constant_pool);
+            },
+            .module => |*module| {
+                try formatInfo(w, depth, indent, "name", module, .name, constant_pool);
+            },
+            .package => |*package| {
+                try formatInfo(w, depth, indent, "name", package, .name, constant_pool);
+            },
+        }
+    }
+
+    pub fn is(self: *const Info, tag: Tag) bool {
+        return @as(Tag, self.*) == tag;
+    }
+};
+
+pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) ParseError!Self {
+    const constant_pool_size = try input.takeInt(u16, .big);
+    const constant_pool = try allocator.alloc(?Info, constant_pool_size - 1);
+    errdefer allocator.free(constant_pool);
+
+    var i: usize = 0;
+    while (i < constant_pool_size - 1) {
+        defer i += 1;
+
+        const info: Info = try .parse(input, allocator);
+        constant_pool[i] = info;
+
+        switch (info) {
+            .long, .double => {
+                i += 1;
+                constant_pool[i] = null;
+            },
+            else => {},
+        }
+    }
+
+    return .{
+        .constant_pool = constant_pool,
+    };
+}
+
+pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
+    for (self.constant_pool) |*info| {
+        if (info.*) |*c| c.deinit(allocator);
+    }
+    allocator.free(self.constant_pool);
+}
+
+pub fn get(self: *const Self, index: u16) ResolveError!Info {
+    const actual_index = index - 1;
+    if (actual_index >= self.constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
+    const info = self.constant_pool[actual_index];
+    if (info == null) return ResolveError.InvalidConstantType;
+    return info.?;
+}
+
+pub fn getOptional(self: *const Self, index: u16) ResolveError!?Info {
+    if (index == 0) return null;
+    return self.get(index);
+}
+
+pub fn getTag(self: *const Self, index: u16, expected_tag: Info.Tag) ResolveError!Info {
+    const info = try self.get(index);
+    if (!info.is(expected_tag)) return ResolveError.InvalidConstantType;
+    return info;
+}
+
+pub fn getTagOptional(self: *const Self, index: u16, expected_tag: Info.Tag) ResolveError!?Info {
+    if (index == 0) return null;
+    return try self.getTag(index, expected_tag);
+}
+
+pub fn getLoadable(self: *const Self, index: u16) ResolveError!Info {
+    const info = try self.get(index);
+    if (!@as(Info.Tag, info).loadable()) return ResolveError.InvalidConstantType;
+    return info;
+}
+
+pub fn getLoadableOptional(self: *const Self, index: u16) ResolveError!?Info {
+    if (index == 0) return null;
+    return self.getLoadable(index);
+}
+
+pub fn formatInfo(
+    w: *std.Io.Writer,
+    depth: usize,
+    indent: u8,
+    comptime name: []const u8,
+    context: anytype,
+    comptime getter: std.meta.DeclEnum(@TypeOf(context.*)),
+    constant_pool: Self,
+) std.Io.Writer.Error!void {
+    const func = @field(@TypeOf(context.*), @tagName(getter));
+
+    try w.splatByteAll(' ', depth * indent);
+    _ = try w.write(name ++ ":\n");
+    const info = func(context, constant_pool) catch return error.WriteFailed;
+    try info.indentedFormat(w, depth, indent + 1, constant_pool);
+}

src/Class/FieldInfo.zig

@@ -3,7 +3,7 @@ const std = @import("std");
 const EnumFlags = @import("../EnumFlags.zig").EnumFlags;
 
 const Class = @import("../Class.zig");
-const ConstantPoolInfo = Class.ConstantPoolInfo;
+const ConstantPool = Class.ConstantPool;
 const AttributeInfo = Class.AttributeInfo;
 const ResolveError = Class.ResolveError;
 
@@ -14,7 +14,7 @@ attributes: []AttributeInfo,
 
 const Self = @This();
 
-pub const FieldFlags = enum(u16) {
+pub const FieldAccessFlags = EnumFlags(enum(u16) {
     public = 0x0001,
     private = 0x0002,
     protected = 0x0004,
@@ -24,15 +24,13 @@ pub const FieldFlags = enum(u16) {
     transient = 0x0080,
     synthetic = 0x1000,
     @"enum" = 0x4000,
-};
+});
 
-pub const FieldAccessFlags = EnumFlags(FieldFlags);
-
-pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) !Self {
-    const access_flags: FieldAccessFlags = .{ .mask = try input.takeInt(u16, .big) };
+pub fn parse(input: *std.Io.Reader, constant_pool: ConstantPool, allocator: std.mem.Allocator) !Self {
+    const access_flags: FieldAccessFlags = .from(try input.takeInt(u16, .big));
     const name_index = try input.takeInt(u16, .big);
     const descriptor_index = try input.takeInt(u16, .big);
-    const attributes = try Class.parseAttributes(input, allocator);
+    const attributes = try Class.parseAttributes(input, constant_pool, allocator);
     return .{
         .access_flags = access_flags,
         .name_index = name_index,
@@ -48,13 +46,12 @@ pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
     allocator.free(self.attributes);
 }
 
-pub fn format(
+pub fn indentedFormat(
     self: *const Self,
     w: *std.Io.Writer,
     depth: usize,
     indent: u8,
-    allocator: std.mem.Allocator,
-    constant_pool: []const ?ConstantPoolInfo,
+    constant_pool: ConstantPool,
 ) std.Io.Writer.Error!void {
     try w.splatByteAll(' ', depth * indent);
     try w.print("flags: {f}\n", .{ self.access_flags });
@@ -62,12 +59,12 @@ pub fn format(
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("name:\n");
     const field_name = self.name(constant_pool) catch return error.WriteFailed;
-    try field_name.format(w, depth, indent + 1, constant_pool);
+    try field_name.indentedFormat(w, depth, indent + 1, constant_pool);
 
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("descriptor:\n");
     const field_descriptor = self.descriptor(constant_pool) catch return error.WriteFailed;
-    try field_descriptor.format(w, depth, indent + 1, constant_pool);
+    try field_descriptor.indentedFormat(w, depth, indent + 1, constant_pool);
 
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("attributes:\n");
@@ -79,23 +76,15 @@ pub fn format(
         try w.splatByteAll(' ', depth * attr_indent);
         try w.print("{d}:\n", .{ j });
 
-        try attribute.format(w, depth, attr_indent + 1, allocator, constant_pool);
+        try attribute.indentedFormat(w, depth, attr_indent + 1, constant_pool);
     }
 }
 
-pub fn name(self: *const Self, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-    const name_index = self.name_index - 1;
-    if (name_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-    const cp_info = constant_pool[name_index];
-    if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-    return cp_info.?;
+pub fn name(self: *const Self, constant_pool: ConstantPool) ResolveError!ConstantPool.Info {
+    return constant_pool.getTag(self.name_index, .utf8);
 }
 
-pub fn descriptor(self: *const Self, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-    const descriptor_index = self.descriptor_index - 1;
-    if (descriptor_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-    const cp_info = constant_pool[descriptor_index];
-    if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-    return cp_info.?;
+pub fn descriptor(self: *const Self, constant_pool: ConstantPool) ResolveError!ConstantPool.Info {
+    return constant_pool.getTag(self.descriptor_index, .utf8);
 }
 

src/Class/MethodInfo.zig

@@ -3,7 +3,7 @@ const std = @import("std");
 const EnumFlags = @import("../EnumFlags.zig").EnumFlags;
 
 const Class = @import("../Class.zig");
-const ConstantPoolInfo = Class.ConstantPoolInfo;
+const ConstantPool = Class.ConstantPool;
 const AttributeInfo = Class.AttributeInfo;
 const ResolveError = Class.ResolveError;
 
@@ -14,7 +14,7 @@ attributes: []AttributeInfo,
 
 const Self = @This();
 
-pub const MethodFlags = enum(u16) {
+pub const MethodAccessFlags = EnumFlags(enum(u16) {
     public = 0x0001,
     private = 0x0002,
     protected = 0x0004,
@@ -27,15 +27,13 @@ pub const MethodFlags = enum(u16) {
     abstract = 0x0400,
     strict = 0x0800,
     synthetic = 0x1000,
-};
+});
 
-pub const MethodAccessFlags = EnumFlags(MethodFlags);
-
-pub fn parse(input: *std.Io.Reader, allocator: std.mem.Allocator) !Self {
-    const access_flags: MethodAccessFlags = .{ .mask = try input.takeInt(u16, .big) };
+pub fn parse(input: *std.Io.Reader, constant_pool: ConstantPool, allocator: std.mem.Allocator) !Self {
+    const access_flags: MethodAccessFlags = .from(try input.takeInt(u16, .big));
     const name_index = try input.takeInt(u16, .big);
     const descriptor_index = try input.takeInt(u16, .big);
-    const attributes = try Class.parseAttributes(input, allocator);
+    const attributes = try Class.parseAttributes(input, constant_pool, allocator);
     return .{
         .access_flags = access_flags,
         .name_index = name_index,
@@ -51,13 +49,12 @@ pub fn deinit(self: *Self, allocator: std.mem.Allocator) void {
     allocator.free(self.attributes);
 }
 
-pub fn format(
+pub fn indentedFormat(
     self: *const Self,
     w: *std.Io.Writer,
     depth: usize,
     indent: u8,
-    allocator: std.mem.Allocator,
-    constant_pool: []const ?ConstantPoolInfo,
+    constant_pool: ConstantPool,
 ) std.Io.Writer.Error!void {
     try w.splatByteAll(' ', depth * indent);
     try w.print("flags: {f}\n", .{ self.access_flags });
@@ -65,12 +62,12 @@ pub fn format(
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("name:\n");
     const method_name = self.name(constant_pool) catch return error.WriteFailed;
-    try method_name.format(w, depth, indent + 1, constant_pool);
+    try method_name.indentedFormat(w, depth, indent + 1, constant_pool);
 
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("descriptor:\n");
     const method_descriptor = self.descriptor(constant_pool) catch return error.WriteFailed;
-    try method_descriptor.format(w, depth, indent + 1, constant_pool);
+    try method_descriptor.indentedFormat(w, depth, indent + 1, constant_pool);
 
     try w.splatByteAll(' ', depth * indent);
     _ = try w.write("attributes:\n");
@@ -82,23 +79,14 @@ pub fn format(
         try w.splatByteAll(' ', depth * attr_indent);
         try w.print("{d}:\n", .{ j });
 
-        try attribute.format(w, depth, attr_indent + 1, allocator, constant_pool);
+        try attribute.indentedFormat(w, depth, attr_indent + 1, constant_pool);
     }
 }
 
-pub fn name(self: *const Self, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-    const name_index = self.name_index - 1;
-    if (name_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-    const cp_info = constant_pool[name_index];
-    if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-    return cp_info.?;
+pub fn name(self: *const Self, constant_pool: ConstantPool) ResolveError!ConstantPool.Info {
+    return constant_pool.getTag(self.name_index, .utf8);
 }
 
-pub fn descriptor(self: *const Self, constant_pool: []const ?ConstantPoolInfo) ResolveError!ConstantPoolInfo {
-    const descriptor_index = self.descriptor_index - 1;
-    if (descriptor_index >= constant_pool.len) return ResolveError.InvalidConstantPoolIndex;
-    const cp_info = constant_pool[descriptor_index];
-    if (cp_info == null or @as(ConstantPoolInfo.Tag, cp_info.?) != .utf8) return ResolveError.InvalidConstantType;
-    return cp_info.?;
+pub fn descriptor(self: *const Self, constant_pool: ConstantPool) ResolveError!ConstantPool.Info {
+    return constant_pool.getTag(self.descriptor_index, .utf8);
 }
-

src/EnumFlags.zig

@@ -10,6 +10,12 @@ pub fn EnumFlags(comptime E: type) type {
 
         pub const empty: Self = .{ .data = 0 };
 
+        pub fn from(mask: BackingInt) Self {
+            return .{
+                .mask = mask,
+            };
+        }
+
         pub fn contains(self: Self, flag: E) bool {
             return (self.mask & @intFromEnum(flag)) != 0;
         }

src/main.zig

@@ -50,10 +50,9 @@ pub fn main(init: std.process.Init) !void {
         },
         else => return err,
     };
-    defer class.deinit();
+    defer class.deinit(allocator);
 
     try stdout.print("{f}", .{ class });
 
     try stdout.flush();
 }
-

testsuite/.gitignore

@@ -0,0 +1,3 @@
+*.class
+!Object.class
+META-INF

testsuite/classes/java/CustomAnnotation.java

@@ -0,0 +1,14 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.annotation.ElementType;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+@CustomAnnotationAnnotation
+public @interface CustomAnnotation {
+    public CustomAnnotationType type();
+
+    public String name() default "Bob";
+}
+

testsuite/classes/java/CustomAnnotationAnnotation.java

@@ -0,0 +1,9 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.annotation.ElementType;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.ANNOTATION_TYPE)
+public @interface CustomAnnotationAnnotation { }
+

testsuite/classes/java/CustomAnnotationType.java

@@ -0,0 +1,5 @@
+public enum CustomAnnotationType {
+    ONE,
+    TWO,
+}
+

testsuite/classes/java/CustomParameterAnnotation.java

@@ -0,0 +1,9 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.annotation.ElementType;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.PARAMETER)
+public @interface CustomParameterAnnotation { }
+

testsuite/classes/java/CustomTypeAnnotation.java

@@ -0,0 +1,9 @@
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.lang.annotation.ElementType;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE_PARAMETER)
+public @interface CustomTypeAnnotation {
+}

testsuite/classes/java/GenericClass.java

@@ -0,0 +1,14 @@
+import java.util.function.Supplier;
+
+public class GenericClass<@CustomTypeAnnotation T> {
+
+    public <T> Supplier<T> getSupplier(T value) {
+        return new Supplier<T>() {
+            @Override
+            public T get() {
+                return value;
+            }
+        };
+    }
+
+}

testsuite/classes/java/Hello.java

@@ -0,0 +1,6 @@
+class Hello {
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+}
+

testsuite/classes/java/Main.java

@@ -1,17 +1,27 @@
 import java.util.function.Supplier;
 
+@CustomAnnotation(type = CustomAnnotationType.ONE, name = "Alice")
 public class Main implements Runnable, Supplier<Integer>, Interface {
     private static final String name = "John";
     private static final int number = 42;
     private static final double funnyNumber = 6.9;
 
-    public static void main() {
-        new Main().sayHello();
+    public static void main(@CustomParameterAnnotation String[] args) {
+        final var main = new Main();
+        main.sayHello();
+
+        try {
+            main.throwSomething();
+        } catch (Throwable e) {
+            System.err.println("Caught " + e.getMessage());
+        } finally {
+            System.err.println("Finally block");
+        }
     }
-    
+
     @Override
     public void run() {
-        Main.main();
+        Main.main(new String[] { "Hello" });
     }
     
     @Override
@@ -37,4 +47,3 @@ public class Main implements Runnable, Supplier<Integer>, Interface {
         private static final String name = "Inner John";
     }
 }
-

testsuite/classes/java/MultiThreading.java

@@ -0,0 +1,22 @@
+import java.util.concurrent.Executors;
+import java.util.stream.IntStream;
+import java.util.concurrent.TimeUnit;
+
+public class MultiThreading {
+    private int number = 0;
+
+    public static void main(String[] args) throws InterruptedException {
+        final var multiThreading = new MultiThreading();
+
+        final var service = Executors.newFixedThreadPool(3);
+        IntStream.range(0, 1000)
+            .forEach(count -> service.submit(multiThreading::increment));
+        service.awaitTermination(1000, TimeUnit.MILLISECONDS);
+
+        System.out.println(multiThreading.number);
+    }
+
+    public synchronized void increment() {
+        number += 1;
+    }
+}

testsuite/classes/java/Record.java

@@ -0,0 +1,2 @@
+public record Record(String name, int age) {}
+

testsuite/classes/kotlin/Main.kt

@@ -0,0 +1,12 @@
+fun main() {
+    println("Hello, world!")
+
+    Test().apply {
+        test = true
+    }
+}
+
+class Test {
+    var test: Boolean = false
+}
+

testsuite/modules/compile-simple-modules.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+javac -g -d outDir --module-source-path simple-modules $(find simple-modules -name "*.java")

testsuite/modules/run-simple-module-app.sh

@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+java --module-path outDir -m main.app/dev.katkak.modules.main.MainApp

testsuite/modules/simple-modules/hello.modules/dev/katkak/modules/hello/HelloInterface.java

@@ -0,0 +1,6 @@
+package dev.katkak.modules.hello;
+
+public interface HelloInterface {
+    void sayHello();
+}
+

testsuite/modules/simple-modules/hello.modules/dev/katkak/modules/hello/HelloModules.java

@@ -0,0 +1,12 @@
+package dev.katkak.modules.hello;
+
+public class HelloModules implements HelloInterface {
+    public static void doSomething() {
+        System.out.println("Hello, Modules!");
+    }
+
+    public void sayHello() {
+        System.out.println("Hello!");
+    }
+}
+

testsuite/modules/simple-modules/hello.modules/module-info.java

@@ -0,0 +1,6 @@
+module hello.modules {
+    exports dev.katkak.modules.hello;
+
+    provides dev.katkak.modules.hello.HelloInterface with dev.katkak.modules.hello.HelloModules;
+}
+

testsuite/modules/simple-modules/main.app/dev/katkak/modules/main/MainApp.java

@@ -0,0 +1,17 @@
+package dev.katkak.modules.main;
+
+import dev.katkak.modules.hello.HelloModules;
+import dev.katkak.modules.hello.HelloInterface;
+
+import java.util.ServiceLoader;
+
+public class MainApp {
+    public static void main(String[] args) {
+        HelloModules.doSomething();
+
+        final var services = ServiceLoader.load(HelloInterface.class);
+        final var service = services.iterator().next();
+        service.sayHello();
+    }
+}
+

testsuite/modules/simple-modules/main.app/module-info.java

@@ -0,0 +1,6 @@
+module main.app {
+    requires hello.modules;
+
+    uses dev.katkak.modules.hello.HelloInterface;
+}
+