`Make[T]` function, which produces a reference to a canonical copy of
the value in the form of a `Handle[T]`.
Two `Handle[T]` are equal if and only if the values used to produce the
handles are equal, allowing programs to deduplicate values and reduce
their memory footprint.
Comparing two `Handle[T]` values is efficient, reducing down to a simple

</pre>

<p>
the variable <code>s</code> of type <code>Slice</code> must be assignable to
the function parameter type <code>S</code> for the program to be valid.
To reduce complexity, type inference ignores the directionality of assignments,
so the type relationship between <code>Slice</code> and <code>S</code> can be
expressed via the (symmetric) type equation <code>Slice ≡<sub>A</sub> S</code>

connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and
[permitted by the Go 1 compatibility rules](/doc/go1compat).
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair
that controls the execution of certain parts of a Go program.

	#line 1 "not-str-lit"
	void __cgo_f_1_5(void) { static const char __cgo_undefined__5[] = (foo); }

This program will not compile, but cgo can use the presence or absence
of an error message on a given line to deduce the information it
needs. The program is syntactically valid regardless of whether each
name is a type or an ordinary identifier, so there will be no syntax
errors that might stop parsing early.

for key, val = range m {
	h(key, val)
}
// key == last map key encountered in iteration
// val == map[key]

var ch chan Work = producer()
for w := range ch {
	doWork(w)
}

// empty a channel
for range ch {}
</pre>


<h3 id="Go_statements">Go statements</h3>

<p>

## Compiler {#compiler}

The build time overhead to building with [Profile Guided Optimization](/doc/pgo) has been reduced significantly.
Previously, large builds could see 100%+ build time increase from enabling PGO.
In Go 1.23, overhead should be in the single digit percentages.

## Assembler {#assembler}

<p><!-- CL 543255 -->
  The runtime now keeps type-based garbage collection metadata nearer to each
  heap object, improving the CPU performance (latency or throughput) of Go programs
  by 1&ndash;3%.
  This change also reduces the memory overhead of the majority Go programs by
  approximately 1% by deduplicating redundant metadata.
  Some programs may see a smaller improvement because this change adjusts the size