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exception.d
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exception.d
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// Written in the D programming language.
/++
This module defines functions related to exceptions and general error
handling. It also defines functions intended to aid in unit testing.
$(SCRIPT inhibitQuickIndex = 1;)
$(BOOKTABLE,
$(TR $(TH Category) $(TH Functions))
$(TR $(TD Assumptions) $(TD
$(LREF assertNotThrown)
$(LREF assertThrown)
$(LREF assumeUnique)
$(LREF assumeWontThrow)
$(LREF mayPointTo)
))
$(TR $(TD Enforce) $(TD
$(LREF doesPointTo)
$(LREF enforce)
$(LREF errnoEnforce)
))
$(TR $(TD Handlers) $(TD
$(LREF collectException)
$(LREF collectExceptionMsg)
$(LREF ifThrown)
$(LREF handle)
))
$(TR $(TD Other) $(TD
$(LREF basicExceptionCtors)
$(LREF emptyExceptionMsg)
$(LREF ErrnoException)
$(LREF RangePrimitive)
))
)
Copyright: Copyright Andrei Alexandrescu 2008-, Jonathan M Davis 2011-.
License: $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0)
Authors: $(HTTP erdani.org, Andrei Alexandrescu) and
$(HTTP jmdavisprog.com, Jonathan M Davis)
Source: $(PHOBOSSRC std/exception.d)
+/
module std.exception;
/// Synopis
@system unittest
{
import core.stdc.stdlib : malloc, free;
import std.algorithm.comparison : equal;
import std.algorithm.iteration : map, splitter;
import std.algorithm.searching : endsWith;
import std.conv : ConvException, to;
import std.range : front, retro;
// use enforce like assert
int a = 3;
enforce(a > 2, "a needs to be higher than 2.");
// enforce can throw a custom exception
enforce!ConvException(a > 2, "a needs to be higher than 2.");
// enforce will return it's input
enum size = 42;
auto memory = enforce(malloc(size), "malloc failed")[0 .. size];
scope(exit) free(memory.ptr);
// collectException can be used to test for exceptions
Exception e = collectException("abc".to!int);
assert(e.file.endsWith("conv.d"));
// and just for the exception message
string msg = collectExceptionMsg("abc".to!int);
assert(msg == "Unexpected 'a' when converting from type string to type int");
// assertThrown can be used to assert that an exception is thrown
assertThrown!ConvException("abc".to!int);
// ifThrown can be used to provide a default value if an exception is thrown
assert("x".to!int().ifThrown(0) == 0);
// handle is a more advanced version of ifThrown for ranges
auto r = "12,1337z32,54".splitter(',').map!(a => to!int(a));
auto h = r.handle!(ConvException, RangePrimitive.front, (e, r) => 0);
assert(h.equal([12, 0, 54]));
assertThrown!ConvException(h.retro.equal([54, 0, 12]));
// basicExceptionCtors avoids the boilerplate when creating custom exceptions
static class MeaCulpa : Exception
{
mixin basicExceptionCtors;
}
e = collectException((){throw new MeaCulpa("diagnostic message");}());
assert(e.msg == "diagnostic message");
assert(e.file == __FILE__);
assert(e.line == __LINE__ - 3);
// assumeWontThrow can be used to cast throwing code into `nothrow`
void exceptionFreeCode() nothrow
{
// auto-decoding only throws if an invalid UTF char is given
assumeWontThrow("abc".front);
}
// assumeUnique can be used to cast mutable instance to an `immutable` one
// use with care
char[] str = " mutable".dup;
str[0 .. 2] = "im";
immutable res = assumeUnique(str);
assert(res == "immutable");
}
import std.range.primitives;
import std.traits;
/++
Asserts that the given expression does $(I not) throw the given type
of `Throwable`. If a `Throwable` of the given type is thrown,
it is caught and does not escape assertNotThrown. Rather, an
`AssertError` is thrown. However, any other `Throwable`s will escape.
Params:
T = The `Throwable` to test for.
expression = The expression to test.
msg = Optional message to output on test failure.
If msg is empty, and the thrown exception has a
non-empty msg field, the exception's msg field
will be output on test failure.
file = The file where the error occurred.
Defaults to `__FILE__`.
line = The line where the error occurred.
Defaults to `__LINE__`.
Throws:
`AssertError` if the given `Throwable` is thrown.
Returns:
the result of `expression`.
+/
auto assertNotThrown(T : Throwable = Exception, E)
(lazy E expression,
string msg = null,
string file = __FILE__,
size_t line = __LINE__)
{
import core.exception : AssertError;
try
{
return expression();
}
catch (T t)
{
immutable message = msg.length == 0 ? t.msg : msg;
immutable tail = message.length == 0 ? "." : ": " ~ message;
throw new AssertError("assertNotThrown failed: " ~ T.stringof ~ " was thrown" ~ tail, file, line, t);
}
}
///
@system unittest
{
import core.exception : AssertError;
import std.string;
assertNotThrown!StringException(enforce!StringException(true, "Error!"));
//Exception is the default.
assertNotThrown(enforce!StringException(true, "Error!"));
assert(collectExceptionMsg!AssertError(assertNotThrown!StringException(
enforce!StringException(false, "Error!"))) ==
`assertNotThrown failed: StringException was thrown: Error!`);
}
@system unittest
{
import core.exception : AssertError;
import std.string;
assert(collectExceptionMsg!AssertError(assertNotThrown!StringException(
enforce!StringException(false, ""), "Error!")) ==
`assertNotThrown failed: StringException was thrown: Error!`);
assert(collectExceptionMsg!AssertError(assertNotThrown!StringException(
enforce!StringException(false, ""))) ==
`assertNotThrown failed: StringException was thrown.`);
assert(collectExceptionMsg!AssertError(assertNotThrown!StringException(
enforce!StringException(false, ""), "")) ==
`assertNotThrown failed: StringException was thrown.`);
}
@system unittest
{
import core.exception : AssertError;
void throwEx(Throwable t) { throw t; }
bool nothrowEx() { return true; }
try
{
assert(assertNotThrown!Exception(nothrowEx()));
}
catch (AssertError) assert(0);
try
{
assert(assertNotThrown!Exception(nothrowEx(), "It's a message"));
}
catch (AssertError) assert(0);
try
{
assert(assertNotThrown!AssertError(nothrowEx()));
}
catch (AssertError) assert(0);
try
{
assert(assertNotThrown!AssertError(nothrowEx(), "It's a message"));
}
catch (AssertError) assert(0);
{
bool thrown = false;
try
{
assertNotThrown!Exception(
throwEx(new Exception("It's an Exception")));
}
catch (AssertError) thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
{
assertNotThrown!Exception(
throwEx(new Exception("It's an Exception")), "It's a message");
}
catch (AssertError) thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
{
assertNotThrown!AssertError(
throwEx(new AssertError("It's an AssertError", __FILE__, __LINE__)));
}
catch (AssertError) thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
{
assertNotThrown!AssertError(
throwEx(new AssertError("It's an AssertError", __FILE__, __LINE__)),
"It's a message");
}
catch (AssertError) thrown = true;
assert(thrown);
}
}
/++
Asserts that the given expression throws the given type of `Throwable`.
The `Throwable` is caught and does not escape assertThrown. However,
any other `Throwable`s $(I will) escape, and if no `Throwable`
of the given type is thrown, then an `AssertError` is thrown.
Params:
T = The `Throwable` to test for.
expression = The expression to test.
msg = Optional message to output on test failure.
file = The file where the error occurred.
Defaults to `__FILE__`.
line = The line where the error occurred.
Defaults to `__LINE__`.
Throws:
`AssertError` if the given `Throwable` is not thrown.
+/
void assertThrown(T : Throwable = Exception, E)
(lazy E expression,
string msg = null,
string file = __FILE__,
size_t line = __LINE__)
{
import core.exception : AssertError;
try
expression();
catch (T)
return;
throw new AssertError("assertThrown failed: No " ~ T.stringof ~ " was thrown"
~ (msg.length == 0 ? "." : ": ") ~ msg,
file, line);
}
///
@system unittest
{
import core.exception : AssertError;
import std.string;
assertThrown!StringException(enforce!StringException(false, "Error!"));
//Exception is the default.
assertThrown(enforce!StringException(false, "Error!"));
assert(collectExceptionMsg!AssertError(assertThrown!StringException(
enforce!StringException(true, "Error!"))) ==
`assertThrown failed: No StringException was thrown.`);
}
@system unittest
{
import core.exception : AssertError;
void throwEx(Throwable t) { throw t; }
void nothrowEx() { }
try
{
assertThrown!Exception(throwEx(new Exception("It's an Exception")));
}
catch (AssertError) assert(0);
try
{
assertThrown!Exception(throwEx(new Exception("It's an Exception")),
"It's a message");
}
catch (AssertError) assert(0);
try
{
assertThrown!AssertError(throwEx(new AssertError("It's an AssertError",
__FILE__, __LINE__)));
}
catch (AssertError) assert(0);
try
{
assertThrown!AssertError(throwEx(new AssertError("It's an AssertError",
__FILE__, __LINE__)),
"It's a message");
}
catch (AssertError) assert(0);
{
bool thrown = false;
try
assertThrown!Exception(nothrowEx());
catch (AssertError)
thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
assertThrown!Exception(nothrowEx(), "It's a message");
catch (AssertError)
thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
assertThrown!AssertError(nothrowEx());
catch (AssertError)
thrown = true;
assert(thrown);
}
{
bool thrown = false;
try
assertThrown!AssertError(nothrowEx(), "It's a message");
catch (AssertError)
thrown = true;
assert(thrown);
}
}
/++
Enforces that the given value is true.
If the given value is false, an exception is thrown.
The
$(UL
$(LI `msg` - error message as a `string`)
$(LI `dg` - custom delegate that return a string and is only called if an exception occurred)
$(LI `ex` - custom exception to be thrown. It is `lazy` and is only created if an exception occurred)
)
Params:
value = The value to test.
E = Exception type to throw if the value evaluates to false.
msg = The error message to put in the exception if it is thrown.
dg = The delegate to be called if the value evaluates to false.
ex = The exception to throw if the value evaluates to false.
file = The source file of the caller.
line = The line number of the caller.
Returns: `value`, if `cast(bool) value` is true. Otherwise,
depending on the chosen overload, `new Exception(msg)`, `dg()` or `ex` is thrown.
Note:
`enforce` is used to throw exceptions and is therefore intended to
aid in error handling. It is $(I not) intended for verifying the logic
of your program. That is what `assert` is for. Also, do not use
`enforce` inside of contracts (i.e. inside of `in` and `out`
blocks and `invariant`s), because contracts are compiled out when
compiling with $(I -release).
If a delegate is passed, the safety and purity of this function are inferred
from `Dg`'s safety and purity.
+/
template enforce(E : Throwable = Exception)
if (is(typeof(new E("", string.init, size_t.init)) : Throwable) ||
is(typeof(new E(string.init, size_t.init)) : Throwable))
{
///
T enforce(T)(T value, lazy const(char)[] msg = null,
string file = __FILE__, size_t line = __LINE__)
if (is(typeof({ if (!value) {} })))
{
if (!value) bailOut!E(file, line, msg);
return value;
}
}
/// ditto
T enforce(T, Dg, string file = __FILE__, size_t line = __LINE__)
(T value, scope Dg dg)
if (isSomeFunction!Dg && is(typeof( dg() )) &&
is(typeof({ if (!value) {} })))
{
if (!value) dg();
return value;
}
/// ditto
T enforce(T)(T value, lazy Throwable ex)
{
if (!value) throw ex();
return value;
}
///
@system unittest
{
import core.stdc.stdlib : malloc, free;
import std.conv : ConvException, to;
// use enforce like assert
int a = 3;
enforce(a > 2, "a needs to be higher than 2.");
// enforce can throw a custom exception
enforce!ConvException(a > 2, "a needs to be higher than 2.");
// enforce will return it's input
enum size = 42;
auto memory = enforce(malloc(size), "malloc failed")[0 .. size];
scope(exit) free(memory.ptr);
}
///
@safe unittest
{
assertNotThrown(enforce(true, new Exception("this should not be thrown")));
assertThrown(enforce(false, new Exception("this should be thrown")));
}
///
@safe unittest
{
assert(enforce(123) == 123);
try
{
enforce(false, "error");
assert(false);
}
catch (Exception e)
{
assert(e.msg == "error");
assert(e.file == __FILE__);
assert(e.line == __LINE__-7);
}
}
/// Alias your own enforce function
@safe unittest
{
import std.conv : ConvException;
alias convEnforce = enforce!ConvException;
assertNotThrown(convEnforce(true));
assertThrown!ConvException(convEnforce(false, "blah"));
}
private void bailOut(E : Throwable = Exception)(string file, size_t line, scope const(char)[] msg)
{
static if (is(typeof(new E(string.init, string.init, size_t.init))))
{
throw new E(msg ? msg.idup : "Enforcement failed", file, line);
}
else static if (is(typeof(new E(string.init, size_t.init))))
{
throw new E(file, line);
}
else
{
static assert(0, "Expected this(string, string, size_t) or this(string, size_t)" ~
" constructor for " ~ __traits(identifier, E));
}
}
@safe unittest
{
// Issue 10510
extern(C) void cFoo() { }
enforce(false, &cFoo);
}
// purity and safety inference test
@system unittest
{
static foreach (EncloseSafe; [false, true])
static foreach (EnclosePure; [false, true])
{
static foreach (BodySafe; [false, true])
static foreach (BodyPure; [false, true])
{{
enum code =
"delegate void() " ~
(EncloseSafe ? "@safe " : "") ~
(EnclosePure ? "pure " : "") ~
"{ enforce(true, { " ~
"int n; " ~
(BodySafe ? "" : "auto p = &n + 10; " ) ~ // unsafe code
(BodyPure ? "" : "static int g; g = 10; ") ~ // impure code
"}); " ~
"}";
enum expect =
(BodySafe || !EncloseSafe) && (!EnclosePure || BodyPure);
version (none)
pragma(msg, "safe = ", EncloseSafe?1:0, "/", BodySafe?1:0, ", ",
"pure = ", EnclosePure?1:0, "/", BodyPure?1:0, ", ",
"expect = ", expect?"OK":"NG", ", ",
"code = ", code);
static assert(__traits(compiles, mixin(code)()) == expect);
}}
}
}
// Test for bugzilla 8637
@system unittest
{
struct S
{
static int g;
~this() {} // impure & unsafe destructor
bool opCast(T:bool)() {
int* p = cast(int*) 0; // unsafe operation
int n = g; // impure operation
return true;
}
}
S s;
enforce(s);
enforce(s, {});
enforce(s, new Exception(""));
errnoEnforce(s);
alias E1 = Exception;
static class E2 : Exception
{
this(string fn, size_t ln) { super("", fn, ln); }
}
static class E3 : Exception
{
this(string msg) { super(msg, __FILE__, __LINE__); }
}
enforce!E1(s);
enforce!E2(s);
}
@safe unittest
{
// Issue 14685
class E : Exception
{
this() { super("Not found"); }
}
static assert(!__traits(compiles, { enforce!E(false); }));
}
/++
Enforces that the given value is true, throwing an `ErrnoException` if it
is not.
Params:
value = The value to test.
msg = The message to include in the `ErrnoException` if it is thrown.
Returns: `value`, if `cast(bool) value` is true. Otherwise,
$(D new ErrnoException(msg)) is thrown. It is assumed that the last
operation set `errno` to an error code corresponding with the failed
condition.
+/
alias errnoEnforce = enforce!ErrnoException;
///
@system unittest
{
import core.stdc.stdio : fclose, fgets, fopen;
auto f = fopen(__FILE_FULL_PATH__, "r").errnoEnforce;
scope(exit) fclose(f);
char[100] buf;
auto line = fgets(buf.ptr, buf.length, f);
enforce(line !is null); // expect a non-empty line
}
// @@@DEPRECATED_2.089@@@
/++
$(RED Deprecated. Please use $(LREF enforce) instead. This function will be removed 2.089.)
If `!value` is `false`, `value` is returned. Otherwise,
$(D new E(msg, file, line)) is thrown. Or if `E` doesn't take a message
and can be constructed with $(D new E(file, line)), then
$(D new E(file, line)) will be thrown.
Example:
--------------------
auto f = enforceEx!FileMissingException(fopen("data.txt"));
auto line = readln(f);
enforceEx!DataCorruptionException(line.length);
--------------------
+/
deprecated("Use `enforce`. `enforceEx` will be removed with 2.089.")
template enforceEx(E : Throwable)
if (is(typeof(new E("", string.init, size_t.init))))
{
/++ Ditto +/
T enforceEx(T)(T value, lazy string msg = "", string file = __FILE__, size_t line = __LINE__)
{
if (!value) throw new E(msg, file, line);
return value;
}
}
/+ Ditto +/
deprecated("Use `enforce`. `enforceEx` will be removed with 2.089.")
template enforceEx(E : Throwable)
if (is(typeof(new E(string.init, size_t.init))) && !is(typeof(new E("", string.init, size_t.init))))
{
/++ Ditto +/
T enforceEx(T)(T value, string file = __FILE__, size_t line = __LINE__)
{
if (!value) throw new E(file, line);
return value;
}
}
deprecated
@system unittest
{
import core.exception : OutOfMemoryError;
import std.array : empty;
assertNotThrown(enforceEx!Exception(true));
assertNotThrown(enforceEx!Exception(true, "blah"));
assertNotThrown(enforceEx!OutOfMemoryError(true));
{
auto e = collectException(enforceEx!Exception(false));
assert(e !is null);
assert(e.msg.empty);
assert(e.file == __FILE__);
assert(e.line == __LINE__ - 4);
}
{
auto e = collectException(enforceEx!Exception(false, "hello", "file", 42));
assert(e !is null);
assert(e.msg == "hello");
assert(e.file == "file");
assert(e.line == 42);
}
{
auto e = collectException!Error(enforceEx!OutOfMemoryError(false));
assert(e !is null);
assert(e.msg == "Memory allocation failed");
assert(e.file == __FILE__);
assert(e.line == __LINE__ - 4);
}
{
auto e = collectException!Error(enforceEx!OutOfMemoryError(false, "file", 42));
assert(e !is null);
assert(e.msg == "Memory allocation failed");
assert(e.file == "file");
assert(e.line == 42);
}
static assert(!is(typeof(enforceEx!int(true))));
}
deprecated
@safe unittest
{
alias enf = enforceEx!Exception;
assertNotThrown(enf(true));
assertThrown(enf(false, "blah"));
}
/++
Catches and returns the exception thrown from the given expression.
If no exception is thrown, then null is returned and `result` is
set to the result of the expression.
Note that while `collectException` $(I can) be used to collect any
`Throwable` and not just `Exception`s, it is generally ill-advised to
catch anything that is neither an `Exception` nor a type derived from
`Exception`. So, do not use `collectException` to collect
non-`Exception`s unless you're sure that that's what you really want to
do.
Params:
T = The type of exception to catch.
expression = The expression which may throw an exception.
result = The result of the expression if no exception is thrown.
+/
T collectException(T = Exception, E)(lazy E expression, ref E result)
{
try
{
result = expression();
}
catch (T e)
{
return e;
}
return null;
}
///
@system unittest
{
int b;
int foo() { throw new Exception("blah"); }
assert(collectException(foo(), b));
int[] a = new int[3];
import core.exception : RangeError;
assert(collectException!RangeError(a[4], b));
}
/++
Catches and returns the exception thrown from the given expression.
If no exception is thrown, then null is returned. `E` can be
`void`.
Note that while `collectException` $(I can) be used to collect any
`Throwable` and not just `Exception`s, it is generally ill-advised to
catch anything that is neither an `Exception` nor a type derived from
`Exception`. So, do not use `collectException` to collect
non-`Exception`s unless you're sure that that's what you really want to
do.
Params:
T = The type of exception to catch.
expression = The expression which may throw an exception.
+/
T collectException(T : Throwable = Exception, E)(lazy E expression)
{
try
{
expression();
}
catch (T t)
{
return t;
}
return null;
}
///
@safe unittest
{
int foo() { throw new Exception("blah"); }
assert(collectException(foo()).msg == "blah");
}
/++
Catches the exception thrown from the given expression and returns the
msg property of that exception. If no exception is thrown, then null is
returned. `E` can be `void`.
If an exception is thrown but it has an empty message, then
`emptyExceptionMsg` is returned.
Note that while `collectExceptionMsg` $(I can) be used to collect any
`Throwable` and not just `Exception`s, it is generally ill-advised to
catch anything that is neither an `Exception` nor a type derived from
`Exception`. So, do not use `collectExceptionMsg` to collect
non-`Exception`s unless you're sure that that's what you really want to
do.
Params:
T = The type of exception to catch.
expression = The expression which may throw an exception.
+/
string collectExceptionMsg(T = Exception, E)(lazy E expression)
{
import std.array : empty;
try
{
expression();
return cast(string) null;
}
catch (T e)
return e.msg.empty ? emptyExceptionMsg : e.msg;
}
///
@safe unittest
{
void throwFunc() { throw new Exception("My Message."); }
assert(collectExceptionMsg(throwFunc()) == "My Message.");
void nothrowFunc() {}
assert(collectExceptionMsg(nothrowFunc()) is null);
void throwEmptyFunc() { throw new Exception(""); }
assert(collectExceptionMsg(throwEmptyFunc()) == emptyExceptionMsg);
}
/++
Value that collectExceptionMsg returns when it catches an exception
with an empty exception message.
+/
enum emptyExceptionMsg = "<Empty Exception Message>";
/**
* Casts a mutable array to an immutable array in an idiomatic
* manner. Technically, `assumeUnique` just inserts a cast,
* but its name documents assumptions on the part of the
* caller. `assumeUnique(arr)` should only be called when
* there are no more active mutable aliases to elements of $(D
* arr). To strengthen this assumption, `assumeUnique(arr)`
* also clears `arr` before returning. Essentially $(D
* assumeUnique(arr)) indicates commitment from the caller that there
* is no more mutable access to any of `arr`'s elements
* (transitively), and that all future accesses will be done through
* the immutable array returned by `assumeUnique`.
*
* Typically, `assumeUnique` is used to return arrays from
* functions that have allocated and built them.
*
* Params:
* array = The array to cast to immutable.
*
* Returns: The immutable array.
*
* Example:
*
* $(RUNNABLE_EXAMPLE
* ----
* string letters()
* {
* char[] result = new char['z' - 'a' + 1];
* foreach (i, ref e; result)
* {
* e = cast(char)('a' + i);
* }
* return assumeUnique(result);
* }
* ----
* )
*
* The use in the example above is correct because `result`
* was private to `letters` and is inaccessible in writing
* after the function returns. The following example shows an
* incorrect use of `assumeUnique`.
*
* Bad:
*
* $(RUNNABLE_EXAMPLE
* ----
* private char[] buffer;
* string letters(char first, char last)
* {
* if (first >= last) return null; // fine
* auto sneaky = buffer;
* sneaky.length = last - first + 1;
* foreach (i, ref e; sneaky)
* {
* e = cast(char)('a' + i);
* }
* return assumeUnique(sneaky); // BAD
* }
* ----
* )
*
* The example above wreaks havoc on client code because it is
* modifying arrays that callers considered immutable. To obtain an
* immutable array from the writable array `buffer`, replace
* the last line with:
*
* ----
* return to!(string)(sneaky); // not that sneaky anymore
* ----
*
* The call will duplicate the array appropriately.
*
* Note that checking for uniqueness during compilation is
* possible in certain cases, especially when a function is
* marked as a pure function. The following example does not
* need to call assumeUnique because the compiler can infer the
* uniqueness of the array in the pure function:
*
* $(RUNNABLE_EXAMPLE
* ----
* string letters() pure
* {
* char[] result = new char['z' - 'a' + 1];
* foreach (i, ref e; result)
* {
* e = cast(char)('a' + i);
* }
* return result;
* }
* ----
* )
*
* For more on infering uniqueness see the $(B unique) and
* $(B lent) keywords in the
* $(HTTP www.cs.cmu.edu/~aldrich/papers/aldrich-dissertation.pdf, ArchJava)
* language.
*
* The downside of using `assumeUnique`'s
* convention-based usage is that at this time there is no
* formal checking of the correctness of the assumption;
* on the upside, the idiomatic use of `assumeUnique` is
* simple and rare enough to be tolerable.
*
*/
immutable(T)[] assumeUnique(T)(T[] array) pure nothrow
{
return .assumeUnique(array); // call ref version
}
/// ditto
immutable(T)[] assumeUnique(T)(ref T[] array) pure nothrow
{
auto result = cast(immutable(T)[]) array;
array = null;
return result;
}
/// ditto
immutable(T[U]) assumeUnique(T, U)(ref T[U] array) pure nothrow
{
auto result = cast(immutable(T[U])) array;
array = null;
return result;
}
///
@system unittest
{
int[] arr = new int[1];
auto arr1 = arr.assumeUnique;
static assert(is(typeof(arr1) == immutable(int)[]));
assert(arr == null);
assert(arr1 == [0]);
}
///
@system unittest
{
int[string] arr = ["a":1];
auto arr1 = arr.assumeUnique;
static assert(is(typeof(arr1) == immutable(int[string])));
assert(arr == null);
assert(arr1.keys == ["a"]);
}