# v1.8.x - yyyy-mm-dd
## Changes affecting backward compatibility
- `httpclient.contentLength` default to `-1` if the Content-Length header is not set in the response, it followed Apache HttpClient(Java), http(go) and .Net HttpWebResponse(C#) behavior. Previously raise `ValueError`.
- `addr` is now available for all addressable locations,
`unsafeAddr` is now deprecated and an alias for `addr`.
- Certain definitions from the default `system` module have been moved to
the following new modules:
- `std/syncio`
- `std/assertions`
- `std/formatfloat`
- `std/objectdollar`
- `std/widestrs`
In the future, these definitions will be removed from the `system` module,
and their respective modules will have to be imported to use them.
Currently, to make these imports required, the `-d:nimPreviewSlimSystem` option
may be used.
- Enabling `-d:nimPreviewSlimSystem` also removes the following deprecated
symbols in the `system` module:
- Aliases with `Error` suffix to exception types that have a `Defect` suffix
(see [exceptions](https://nim-lang.org/docs/exceptions.html)):
`ArithmeticError`, `DivByZeroError`, `OverflowError`,
`AccessViolationError`, `AssertionError`, `OutOfMemError`, `IndexError`,
`FieldError`, `RangeError`, `StackOverflowError`, `ReraiseError`,
`ObjectAssignmentError`, `ObjectConversionError`, `FloatingPointError`,
`FloatOverflowError`, `FloatUnderflowError`, `FloatInexactError`,
`DeadThreadError`, `NilAccessError`
- `addQuitProc`, replaced by `exitprocs.addExitProc`
- Legacy unsigned conversion operations: `ze`, `ze64`, `toU8`, `toU16`, `toU32`
- `TaintedString`, formerly a distinct alias to `string`
- `PInt32`, `PInt64`, `PFloat32`, `PFloat64`, aliases to
`ptr int32`, `ptr int64`, `ptr float32`, `ptr float64`
- The `gc:v2` option is removed.
- The `mainmodule` and `m` options are removed.
- The `threads:on` option is now the default.
- Optional parameters in combination with `: body` syntax (RFC #405) are now opt-in via
`experimental:flexibleOptionalParams`.
- Automatic dereferencing (experimental feature) is removed.
- The `Math.trunc` polyfill for targeting Internet Explorer was
previously included in most JavaScript output files.
Now, it is only included with `-d:nimJsMathTruncPolyfill`.
If you are targeting Internet Explorer, you may choose to enable this option
or define your own `Math.trunc` polyfill using the [`emit` pragma](https://nim-lang.org/docs/manual.html#implementation-specific-pragmas-emit-pragma).
Nim uses `Math.trunc` for the division and modulo operators for integers.
- `shallowCopy` and `shallow` are removed for ARC/ORC. Use `move` when possible or combine assignment and
`sink` for optimization purposes.
- The `nimPreviewDotLikeOps` define is going to be removed or deprecated.
- The `{.this.}` pragma, deprecated since 0.19, has been removed.
- `nil` literals can no longer be directly assigned to variables or fields of `distinct` pointer types. They must be converted instead.
```nim
type Foo = distinct ptr int
# Before:
var x: Foo = nil
# After:
var x: Foo = Foo(nil)
```
- Removed two type pragma syntaxes deprecated since 0.20, namely
`type Foo = object {.final.}`, and `type Foo {.final.} [T] = object`.
- [Overloadable enums](https://nim-lang.github.io/Nim/manual.html#overloadable-enum-value-names) and Unicode Operators
are no longer experimental.
- Removed the `nimIncrSeqV3` define.
- Static linking against OpenSSL versions below 1.1, previously done by
setting `-d:openssl10`, is no longer supported.
- `macros.getImpl` for `const` symbols now returns the full definition node
(as `nnkConstDef`) rather than the AST of the constant value.
- Lock levels are deprecated, now a noop.
- ORC is now the default memory management strategy. Use
`--mm:refc` for a transition period.
- `strictEffects` are no longer experimental.
Use `legacy:laxEffects` to keep backward compatibility.
- The `gorge`/`staticExec` calls will now return a descriptive message in the output
if the execution fails for whatever reason. To get back legacy behaviour use `-d:nimLegacyGorgeErrors`.
## Standard library additions and changes
[//]: # "Changes:"
- OpenSSL version 3 is now supported by setting either `-d:sslVersion=3` or `-d:useOpenssl3`.
- `macros.parseExpr` and `macros.parseStmt` now accept an optional
filename argument for more informative errors.
- Module `colors` expanded with missing colors from the CSS color standard.
`colPaleVioletRed` and `colMediumPurple` have also been changed to match the CSS color standard.
- Fixed `lists.SinglyLinkedList` being broken after removing the last node ([#19353](https://github.com/nim-lang/Nim/pull/19353)).
- The `md5` module now works at compile time and in JavaScript.
- `std/smtp` sends `ehlo` first. If the mail server does not understand, it sends `helo` as a fallback.
- Changed `mimedb` to use an `OrderedTable` instead of `OrderedTableRef` to support `const` tables.
- `strutils.find` now uses and defaults to `last = -1` for whole string searches,
making limiting it to just the first char (`last = 0`) valid.
- `random.rand` now works with `Ordinal`s.
- Undeprecated `os.isvalidfilename`.
- `std/oids` now uses `int64` to store time internally (before it was int32).
[//]: # "Additions:"
- Added ISO 8601 week date utilities in `times`:
- Added `IsoWeekRange`, a range type for weeks in a week-based year.
- Added `IsoYear`, a distinct type for a week-based year in contrast to a regular year.
- Added a `initDateTime` overload to create a datetime from an ISO week date.
- Added `getIsoWeekAndYear` to get an ISO week number and week-based year from a datetime.
- Added `getIsoWeeksInYear` to return the number of weeks in a week-based year.
- Added `std/oserrors` for OS error reporting. Added `std/envvars` for environment variables handling.
- Added `sep` parameter in `std/uri` to specify the query separator.
- Added bindings to [`Array.shift`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/shift)
and [`queueMicrotask`](https://developer.mozilla.org/en-US/docs/Web/API/queueMicrotask)
in `jscore` for JavaScript targets.
- Added `UppercaseLetters`, `LowercaseLetters`, `PunctuationChars`, `PrintableChars` sets to `std/strutils`.
- Added `complex.sgn` for obtaining the phase of complex numbers.
- Added `insertAdjacentText`, `insertAdjacentElement`, `insertAdjacentHTML`,
`after`, `before`, `closest`, `append`, `hasAttributeNS`, `removeAttributeNS`,
`hasPointerCapture`, `releasePointerCapture`, `requestPointerLock`,
`replaceChildren`, `replaceWith`, `scrollIntoViewIfNeeded`, `setHTML`,
`toggleAttribute`, and `matches` to `std/dom`.
- Added [`jsre.hasIndices`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/hasIndices)
- Added `capacity` for `string` and `seq` to return the current capacity, see https://github.com/nim-lang/RFCs/issues/460
[//]: # "Deprecations:"
- Deprecated `selfExe` for Nimscript.
- Deprecated `std/sums`.
- Deprecated `std/base64.encode` for collections of arbitrary integer element type.
Now only `byte` and `char` are supported.
[//]: # "Removals:"
- Removed deprecated module `parseopt2`.
- Removed deprecated module `sharedstrings`.
- Removed deprecated module `dom_extensions`.
- Removed deprecated module `LockFreeHash`.
- Removed deprecated module `events`.
- Removed deprecated `oids.oidToString`.
- Removed define `nimExperimentalAsyncjsThen` for `std/asyncjs.then` and `std/jsfetch`.
- Removed deprecated `jsre.test` and `jsre.toString`.
- Removed deprecated `math.c_frexp`.
- Removed deprecated `` httpcore.`==` ``.
- Removed deprecated `std/posix.CMSG_SPACE` and `std/posix.CMSG_LEN` that takes wrong argument types.
- Removed deprecated `osproc.poDemon`, symbol with typo.
## Language changes
- [Tag tracking](https://nim-lang.github.io/Nim/manual.html#effect-system-tag-tracking) supports the definition of forbidden tags by the `.forbids` pragma
which can be used to disable certain effects in proc types.
- [Case statement macros](https://nim-lang.github.io/Nim/manual.html#macros-case-statement-macros) are no longer experimental,
meaning you no longer need to enable the experimental switch `caseStmtMacros` to use them.
- Full command syntax and block arguments i.e. `foo a, b: c` are now allowed
for the right-hand side of type definitions in type sections. Previously
they would error with "invalid indentation".
- `defined` now accepts identifiers separated by dots, i.e. `defined(a.b.c)`.
In the command line, this is defined as `-d:a.b.c`. Older versions can
use accents as in ``defined(`a.b.c`)`` to access such defines.
- [Macro pragmas](https://nim-lang.github.io/Nim/manual.html#userminusdefined-pragmas-macro-pragmas) changes:
- Templates now accept macro pragmas.
- Macro pragmas for var/let/const sections have been redesigned in a way that works
similarly to routine macro pragmas. The new behavior is documented in the
[experimental manual](https://nim-lang.github.io/Nim/manual_experimental.html#extended-macro-pragmas).
- Pragma macros on type definitions can now return `nnkTypeSection` nodes as well as `nnkTypeDef`,
allowing multiple type definitions to be injected in place of the original type definition.
```nim
import macros
macro multiply(amount: static int, s: untyped): untyped =
let name = $s[0].basename
result = newNimNode(nnkTypeSection)
for i in 1 .. amount:
result.add(newTree(nnkTypeDef, ident(name & $i), s[1], s[2]))
type
Foo = object
Bar {.multiply: 3.} = object
x, y, z: int
Baz = object
# becomes
type
Foo = object
Bar1 = object
x, y, z: int
Bar2 = object
x, y, z: int
Bar3 = object
x, y, z: int
Baz = object
```
- Redefining templates with the same signature implicitly was previously
allowed to support certain macro code. A `{.redefine.}` pragma has been
added to make this work explicitly, and a warning is generated in the case
where it is implicit. This behavior only applies to templates, redefinition
is generally disallowed for other symbols.
- A new form of type inference called [top-down inference](https://nim-lang.github.io/Nim/manual_experimental.html#topminusdown-type-inference)
has been implemented for a variety of basic cases. For example, code like the following now compiles:
```nim
let foo: seq[(float, byte, cstring)] = @[(1, 2, "abc")]
```
- `cstring` is now accepted as a selector in `case` statements, removing the
need to convert to `string`. On the JS backend, this is translated directly
to a `switch` statement.
## Compiler changes
- The `gc` switch has been renamed to `mm` ("memory management") in order to reflect the
reality better. (Nim moved away from all techniques based on "tracing".)
- Defines the `gcRefc` symbol which allows writing specific code for the refc GC.
- `nim` can now compile version 1.4.0 as follows: `nim c --lib:lib --stylecheck:off compiler/nim`,
without requiring `-d:nimVersion140` which is now a noop.
- `--styleCheck`, `--hintAsError` and `--warningAsError` now only apply to the current package.
- The switch `--nimMainPrefix:prefix` has been added to add a prefix to the names of `NimMain` and
related functions produced on the backend. This prevents conflicts with other Nim
static libraries.
- When compiling for Release the flag `-fno-math-errno` is used for GCC.
## Tool changes
- Nim now supports Nimble version 0.14 which added support for lock-files. This is done by
a simple configuration change setting that you can do yourself too. In `$nim/config/nim.cfg`
replace `pkgs` by `pkgs2`.