V 0.4

1 July 2023

Improvements in the language

• Coroutines with a scheduler. Only Linux/macOS for now, requires -use-coroutines and coroutines.sleep() instead of time.sleep(). They work with IO and net, but not with GC for now.
• spawn now spawns system threads, go spawns coroutines.
• Static type methods: Foo.new() to replace factory functions like new_foo().
• Smartcasting with complex conditions:if sum_type is Foo && !sum_type.is_info && get_name(sum_type.info.name) == 'foo' .
• Functions can now return fixed size arrays.
• Enum values now can have attributes.
• Generic functions as function parameters are now supported: fn f[T](x T, i int, f_ Fn[T]) T { .
• Anonymous structs can no longer have attributes.
• A new [spawn_stack: 131072] function attribute for controlling the max size of the stack of the spawned threads.
• Channel pop now works with an or block: ch := <-self.item or { return none }
• it has been renamed to index in array inits.
• String interpolation simplified to just '${name}', enforced by vfmt, and updated in the entire code base.
• go foo() has been replaced with spawn foo() (launches an OS thread, go will be used for upcoming coroutines instead).
• vfmt now supports // vfmt off and // vfmt on for turning off the formatting locally for short snippets of code. Useful for keeping your carefully arranged matrices intact.
• Match branch range expressions with consts: match x { const1...const2 {} }
• Hot code reloading via [live] is now supported in imported modules, not just the main module.
• Syntax sugar for map inits without needing explicit casts for interfaces: all.children := { "abc": rect, "def": ui.rectangle()}.
• $embed_file() fixes, including variable args support.
• none fixes: no longer allowed to be used as a separate type, dump() support, not allowed inside unsafe.
• Const functions: const y = term.yellow, then println(y('abc')).
• Builtin type names can no longer be used as identifiers.
• Generic typeof[T](), sizeof[T](), isreftype[T]() functions.
• Deprecated -error-limit in favour of the documented -message-limit option.
• Maps now support aliased keys.
• Operator overloading now works with reference types.
• Generic struct inits with nested generic structs and generic optional types are now allowed.
• During array creation, len: is required when using default values for the array.
• Optimized one byte []u8 arrays creation.
• Recursive aliasing is no longer allowed (e.g. type Alias = map[string]Alias).
• Easier custom error creation: return MyCustomErr{} instead of return IError(MyCustomErr).
• All floats outputs now have .0 conditionally appended to them to improve clarity.
• Custom integer enum types: enum Xyz as u64 {.
• AST transformer fixes and optimizations.
• Stylistic improvements and bug fixes in vfmt.
• Casting integers to enums now requires unsafe{}.
• Improved error and warning messages.
• Parallel compilation now uses sync.Pool.
• -skip-unused fixes, soon to be made the default.
• Anonymous structs.
• Lots of bug fixes: 90% of all bugs ever submitted are closed.
• New keyword/type: nil. Only to be used inside unsafe. Replaces voidptr(0).
• V can now find code in the src/ directory. This allows making V repos much cleaner.
• Support assert condition, extra_message, where the extra_message will be evaluated and shown if the assertion fails.
• Operator overloading now works with aliases and generics.
• Scanner optimizations.
• Using C's #define is no longer allowed in normal V code, only in .c.v files.

Breaking changes

• byte deprecated in favor of u8 (byte is automatically converted to u8 by vfmt).
• json: enums are serialized as strings by default, [json_as_number] attribute can be used for the old behavior.
• Variable shadowing has been completely banned (previously variable names could conflict with module names).
• [] is now used for generics instead of <>.
• Accessing a pointer map value requires an or {} block outside unsafe.
• Anonymous sumtypes have been removed (deprecated for now) due to complicating the language and the compiler too much.

Checker improvements/fixes

• Disallow Result type aliases (type Foo = !Bar) and Result in maps (map[key]!Type).
• Add a missing check for taking address of literal value member.
• Fixed map initialization for maps with option values.
• Allow a << none, where a is []?&int.
• Disallow multiple else branches in a match.
• Fix index expression with sumtype of array types.
• Remove hardcoded check for function calls for C.stat, C.sigaction, etc.
• Fix multiple embedded external module interface.
• Fix missing check for diff type on map value declaration.
• Simplify error handling in the checker (#18507).
• Option alias fixes.
• Fix alias to struct ptr on struct init.
• Sumtypes can no longer hold references.
• Fix a bug checking generic closures.
• A hard to reach limit of 1 million iterations for resolving all generics.
• Fix missing check for unwrapped shift operation.
• Fix enum max value validation.
• Add a missing mutability check for array.delete calls.
• Disallow _ = <- quit.
• Disallow type matching with primitive vars.
• Warning instead of error for unnecessary brackets in if/match.
• Include import aliases when checking for import duplicates.
• Fix infering generic array type in nested call.
• Allow casted enum val and const as fixed array size.
• Disallow multiple return values in const declarations.
• Fix contains() with array of interfaces.
• Disallow mut for blank idents.
• If guards now work with struct fields which are Option functions. Such fields can now also be assigned to other fields/variables.
• Option receivers can no longer have methods.
• none can now be cast to all Option types, including aliases.
• Option references are now supported: ?&Type.
• Arrays of Options are now allowed.
• Allow foo := Foo{}, when Foo has an Option field, that is a struct, that has a [required] tag on its fields.
• Enums can no longer be initialized like structs.
• Capture variables can no longer shadow anonymous function params.
• Mixing multi-return results with other types in return statements is no longer allowed.
• Assigning anonymous structs to named structs is no longer allowed.
• [required] fields are now checked for embedded structs.
• Fixed a bug with closures with fixed array variables.
• Builtin methods first/last/repeat can now be used in custom user types (previously they only worked in builtin arrays).
• Generic struct initialization no longer needs explicit types to be provided:

  struct Foo[T, U] {
  	a T
  	b U
  }
  
  foo := Foo{
  	a: 2
  	b: 'x'
  }
  
  println(foo)
  

• unsafe: dereferencing nil references is no longer allowed in the following case:

  a := unsafe { nil }
  println(*a)
  

• Lots of fixes in the type checker.
• Int signedness mismatch is now checked: cannot use literal signed integer as u8.
• Improved type checker: lots of new type checks and fixed checker bugs.
• Unused last expression in if is now checked.
• Anonymous structs visibility issues fixed.
• More type checks.
• Lots of fixes in shared types.

Standard library

• json: Enum value string serialization supports [json:'alias'] to change its string values.
• Struct fields can now be skipped during JSON/ORM serialization via [json:'-'] and [sql:'-'], in addition to [skip]. This allows having custom behavior for different serialization methods.
• builtin: heap usage API (gc_memory_use() and gc_heap_usage())
• math.big: refactoring, gcd fixes/improvements, overflow fixes, mod_inverse.
• flag: fix finalize with multiple shortargs.
• runtime: add new functions total_memory/0 and free_memory/0.
• time: small cleanup of parse_iso8601 comments, make the C.strftime declaration forwards compatible
• stbi: allow customization of number of channels in stbi.load().
• stbi: add a resize_uint8 function for resizing images in memory.
• time, x.json2: improve iso8601 time decoding.
• builtin: zero out internal map/array pointers on m.free(), to reduce the work for the GC mark phase for non escaping maps/arrays, used in hot loops.
• time: add more detailed error descriptions, add custom format parsing with time.parse_format.
• sync: add Mutex.destroy and RwMutex.destroy methods.
• datatypes: add Bloom filter.
• rand: add missing rand.u16(), update doc comments, add test.
• builtin: speed up string methods with vmemcpy instead of for loop for copying data.
• Added new termios module.
• net.ssl: types using ssl contexts can now be converted to strings via .str()/printed via println().
• v.reflection: added type symbol info metadata.
• crypto and math modules have been updated to use Result instead of Option.
• datatypes.LinkedList[map] now works correctly.
• urllib.Values.get() now returns an Option.
• strconv: v_printf() was made private, v_sprintf() was deprecated. String interpolation should be used instead.
• net.http: mime types have been updated to include all official types.
• gg: create_image() now returns !Image instead of Image, allowing to handle errors.
• sokol: errors during image creation no longer result in a panic, but can be handled by the programmer.
• sokol: macOS apps can now be quit using Cmd+Q.
• os.hostname() and os.loginname() now return Result.
• strconv.atoi optimizations.
• println() now supports arrays with recursive references.
• termux: support for cross-compilation from termux to other platforms.
• readline module now works much better on macOS: key navigation, history, etc (now on par with Linux).
• os: fixed a memleak in getline().
• os.Process now has a create_no_window option (Windows only).
• os.Process now has a set_work_folder() method to set the initial working folder of the new child process.
• math.vec module for generic vector math including 2D, 3D, and 4D vector operations.
• Builtin stb_image.h used by gg has been updated to the latest v2.28.
• All of vlib has been updated to use separate Option/Result types.
• To avoid confusion, all references in the code and documentation to Optional have been replaced with Option.
• gg.Context pipeline has more effects, including the additive effect.
• Much cleaner eof checks in os: refactor err == IError(os.Eof{}) to err is os.Eof.
• Lots of work on x.json2, the pure V json encoder, soon to become official.
• New v.reflection module for runtime reflection.
• Improved os.mv(), which now works consistently even across different windows drives/mount points.
• string.trim_indent(), useful with multi line strings, that start/end with new lines and indentation.
• Reduced memory consumption in the crypto modules.
• Official V UI library is now licensed under MIT.
• Deprecated math.util and math.mathutil have been removed.
• New time format support: time.format_rfc3339().
• encoding.html.escape().
• All public functions in the hash and encoding.base32 modules have been documented.
• New crypto.pem module.
• New map.reserve() method.
• net.ssl has been migrated from a dynamically linked OpenSSL to a statically linked Mbed TLS. This means that V binaries will no longer have an OpenSSL dependency. OpenSSL can still be enabled via -d use_openssl.
• msgpack module for decoding/encoding msgpack. (v install msgpack)
• Most of vlib has been updated to use the new Option/Result types.
• net, net.http, vweb bugs and fixes.
• QuadTree and RingBuffer types in datatypes.
• Forward iterator for datatypes.LinkedList<T>, forward and backward iterators for datatypes.DoublyLinkedList<T>.
• A new maps module, similar to existing arrays. It has generic filter, flatten, invert, to_map, to_array, from_array functions.
• utf8.is_number(), utf8.is_space() functions.
• New encoding.base32 module.
• gg.TouchPoint to differentiate between different types of touch input.
• str.int() conversion speedup (without -prod).
• os.mkdir() now has an optional mode parameter.
• encoding.csv is now generic, supports bools, accepts a custom delimiter, and is compatible with io.Reader/io.Writer.
• datatypes module now uses operator overloading.
• All datatypes types can be converted to V arrays.
• smtp improvements including multiple recipients and base64/utf8 support.
• arrays.carray_to_varray<T>() for converting C arrays to V arrays.
• strconv.v_sprintf() has been deprecated in favor of string interpolation.
• TOML module now supports [toml:...] attributes, just like the JSON module.
• os.walk() is no longer recursive (still works the same).
• io has been migrated to Result.
• Third party window control in Sokol.
• string.replace_char(), math.round_sig().
• Improved multiplication performance in math.big.

Web

• The builtin websocket library is now thread safe.
• Enhanced builtin csrf protection in vweb.
• vweb: ability to set and get values on vweb.Context.
• vweb: support for host specific static files.
• vweb: host option added to controller, and a new host attribute.
• vweb: middleware docs improved; same with docs for [vweb_global] and shared.
• vweb: return 404 on file not found.
• net.http: copy IANA's list of methods to the http.Method enum.
• net.conv: use a pure V implementation instead of C.hton etc.
• net.html: get_tag() methods to find first tag occurrence.
• net.html: fixed text parsing for inline tags.
• net.html: fix parsing of nested quoted strings in code tags.
• picoev: FreeBSD support.
• vweb now supports live page reloading. The web app is instantly updated in the browser (no need to refresh the page) every time a .v or a .html file is changed.
• vweb is now significantly faster and more stable under load, due to a new multithreaded worker pool, which is much more efficient at spreading the workload among all threads equally.
• vweb now supports middleware.
• vweb now supports controllers. It's now possible to have multiple app structs to better separate logic.
• vweb now supports overridable .not_found() method for custom 404 pages in vweb.
• vweb now uses database pool.
• Fixed multipart form parsing in vweb.
• Improved vweb stability under load.
• vweb.csrf module.
• net.urllib ipv6 support.
• net.Http.Response.text renamed to body.
• net.websocket timeout is now configurable.

ORM

• Fixed a foreign key bug that could result in an extra insert.
• Comptime bug with [skip] and [sql:'-'] fixed.
• Checker error for unsupported field types.
• Allow structs without the id field, more flexible primary keys.
• Improved docs and examples.
• Uninitialized structs are no longer inserted into related tables.
• All ORM queries now return ![] (Result of an array). This allows handling/propagating DB errors and simplifies working with ORM (one way).
• Many ORM improvements: type checks for limit/offset/order by/where; support of reference objects in insert; struct fields can be used with limit/offset; Connection interface.
• ORM now supports the like operator:

  users := sql db {
      select from User where name like 'Bob%'
  }
  

• A new -d trace_orm option to see all SQL queries generated and used by V ORM and -d trace_pg_error to trace PG errors.
• Various ORM fixes and improvements, including string interpolation support, type checks, fn calls in where.
• Support parenthesized expressions like select from User where (name == 'Sam' && is_customer == true) || id == 1.
• ORM functions now return Result, so the errors can be handled.

Database drivers

• mysql: TIMESTAMP support.
• mysql: allocate memory for each string and blob dynamically depending on its value length.
• mysql: add the ability to commit transactions.
• VFS support in the builtin sqlite module; sqlite.get_affected_rows_count().
• Improved pg compatibility with older PostgreSQL versions before 2014.
• sqlite, pg, mysql have been moved to db.sqlite, db.pg, db.mysql.

Native backend

• Refactoring, splitting large files into multiple.
• Lots of fixes and new features in the native backend, including making codegen logic platform independent.
• Operator support for floats, multi return.
• Lots of native backend improvements, including library calls, comptime conditionals, enums, method definitions/calls, structs.
• Major improvements to the fast native backend including linking support on Linux. The goal is to be able to self host V soon.

V interpreter

• Some further interpreter work.

C backend

• Fix code generation for generic unions.
• Fix [N]chan (fixed arrays of channels).
• Fix nested fixed array instantiation.
• Fix fixed array of map.
• Fix stringification of usize struct fields (before, they were treated as 32 bit signed numbers).
• Now code generated by the С backend, can be compiled by a C++20 compiler.
• C backend does not generate unused interface functions now.
• Parallelized cc step. Speeds up -prod and clang/gcc compilation by 300-500% (depending on the number of cores). Experimental and hidden behind a -parallel-cc flag, soon to be the default.
• Intel C compiler support.
• Go backend fixes.
• #preinclude for low level C interop.

WASM backend

• A new pure WASM backend, based on binaryen, a WASM builtin module, and a pure V WASM serialization library.

Comptime

• A new $res comptime function to get returned value in defer block (#18382).
• Fix comptimeselector option propagation.
• A mutability check for comptime assignments.
• Fix comptime assigning to sumtype or indexexpr.
• Make comptime calls work with or-block.
• Compile-time interface fields evaluation.
• Compile-time enum evaluation:

  $for item in MyEnum.fields {
      println(item.value)
      println(item.name)
  }
  

• Added $option as a compile-time reflection type representing an any Option type.
• All special compile-time reflection types are now lowercase ($int, $enum, $option, etc).
• Improved compile time checks, like $if x is Type {; $if T in [$array, $struct, $alias, $function] {.
• $for in works with alias types.
• New comptime features for fields: field.is_<field>, field.is_alias, field.is_enum.

Compiler CLI

• v share file.v for sharing code via the playground.
• v up speed up for when it hasn't been run for a long time (vc/ bootstrapping has been optimized).
• v init no longer overwrites existing src/main.v.
• v self now uses a faster TCC backend on macOS (Intel/Apple Silicon), just like on Windows/Linux.
• A new command line flag -e for running short V programs on command line: v -e "println(2+5)" ( works just like in Perl).
• A new -ldflags option, in addition to -cflags. Works just like LDFLAGS in C.

OS support

• Added basic QNX support.
• Installation instructions for using V on NixOS.
• Better make support for OpenBSD.
• Much improved experience for v install pcre on Windows (it now bundles its own .c files, so it compiles cleanly, even if the platform does not have another pcre package installed).
• V can now be compiled with tcc on latest macOS and Apple Silicon.
• Removed the need for the [console] attribute in Windows GUI apps.
• More precise WINAPI declarations for easier integration on Windows.
• More CI tests on FreeBSD.
• Full termux support via $if termux {, more predictable logging on Android.
• Older macOS support (<10.12).
• Windows code has been removed from v.c distributed on non-Windows systems. (v_windows.c is used on Windows.)

Tooling

• A new VPM site: vpm.vlang.io. A better design, discoverability of packages, descriptions, most downloaded packages etc.
• vpm: installation of mixed modules.
• v ls --install -p D:\path\vls.exe to install a local vls executable.
• vdoc: highlight comments with gray color.
• vet: allow vetting files with global variables.
• Make util.launch_tool/3 more robust, by recompiling V tools always in a known current working folder.
• Lots of documentation/readme improvements.
• Lots of playground improvements: play.vlang.io, including a really cool feature: "Show generated C code".
• "Is V still fast?" web-page has been sped up by splitting the result table into multiple years.
• GitHub Copilot summaries in PRs.
• fast.vlang.io fixes & improvements, new server.
• New official IntelliJ plugin: https://intellij-v.github.io.
• Lots of new language documentation, a nicer table of contents.
• Improved documentation for most of the vlib modules
• make.bat & v up improvements on Windows.
• TeamCity test runner support via v -test-runner teamcity foo_test.v.
• CI optimizations for faster runs.
• New official AdventOfCode repo with AOC solutions, also added to CI.
• More detailed timings in v -show-timings.
• v new <name> web for quickly scaffolding new web projects.
• New stunning playground with an improved look and feel, a much better and more responsive editor, code sharing by link, more convenient keyboard control, reusability for potential embedding: https://play.vlang.io.
• Improved call tracing via -trace-calls.
• Lots of documentation improvements, including a better documentation of the recent Option/Result split.
• V REPL: Home/End keys support. Lots of clean up.
• DOOM is now translated/compiled and launched on CI servers. A screenshot of the running game is made via vgret and is compared to the expected result.
• VLS performance improvements, especially on Windows.
• v ls tool for installing, for updating, and for launching VLS (V Language Server).
• v doc now has syntax highlighting.