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Merge branch 'BraedonWooding-patch-3'

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Andrew Kelley 2018-05-24 20:59:39 -04:00
commit af7073b779
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doc/langref.html.in
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@ -3111,7 +3111,48 @@ test "error union" {
{#code_end#}
<p>TODO the <code>||</code> operator for error sets</p>
{#header_open|Inferred Error Sets#}
<p>TODO</p>
<p>
Because many functions in Zig return a possible error, Zig supports inferring the error set.
To infer the error set for a function, use this syntax:
</p>
{#code_begin|test#}
// With an inferred error set
pub fn add_inferred(comptime T: type, a: T, b: T) !T {
var answer: T = undefined;
return if (@addWithOverflow(T, a, b, &answer)) error.Overflow else answer;
}
// With an explicit error set
pub fn add_explicit(comptime T: type, a: T, b: T) Error!T {
var answer: T = undefined;
return if (@addWithOverflow(T, a, b, &answer)) error.Overflow else answer;
}
const Error = error {
Overflow,
};
const std = @import("std");
test "inferred error set" {
if (add_inferred(u8, 255, 1)) |_| unreachable else |err| switch (err) {
error.Overflow => {}, // ok
}
}
{#code_end#}
<p>
When a function has an inferred error set, that function becomes generic and thus it becomes
trickier to do certain things with it, such as obtain a function pointer, or have an error
set that is consistent across different build targets. Additionally, inferred error sets
are incompatible with recursion.
</p>
<p>
In these situations, it is recommended to use an explicit error set. You can generally start
with an empty error set and let compile errors guide you toward completing the set.
</p>
<p>
These limitations may be overcome in a future version of Zig.
</p>
{#header_close#}
{#header_close#}
{#header_open|Error Return Traces#}
@ -3878,7 +3919,16 @@ pub fn main() void {
</p>
{#header_close#}
{#header_open|@ArgType#}
<p>TODO</p>
<pre><code class="zig">@ArgType(comptime T: type, comptime n: usize) -&gt; type</code></pre>
<p>
This builtin function takes a function type and returns the type of the parameter at index <code>n</code>.
</p>
<p>
<code>T</code> must be a function type.
</p>
<p>
Note: This function is deprecated. Use {#link|@typeInfo#} instead.
</p>
{#header_close#}
{#header_open|@atomicLoad#}
<pre><code class="zig">@atomicLoad(comptime T: type, ptr: &amp;const T, comptime ordering: builtin.AtomicOrder) -&gt; T</code></pre>