<pre class="grammar">
"var" IdentifierList = ExpressionList .
</pre>

<pre>
i, j := 0, 10
f := func() int { return 7 }
ch := make(chan int)
r, w, _ := os.Pipe()  // os.Pipe() returns a connected pair of Files and an error, if any
_, y, _ := coord(p)   // coord() returns three values; only interested in y coordinate
</pre>

<p>
Unlike regular variable declarations, a short variable declaration may <i>redeclare</i>

		if p.arch.InFamily(sys.ARM, sys.ARM64) {
			// Special form
			// ARM: destination register pair (R1, R2).
			// ARM64: register pair (R1, R2) for LDP/STP.
			if prefix != 0 || scale != 0 {
				p.errorf("illegal address mode for register pair")
				return
			}
			a.Type = obj.TYPE_REGREG
			a.Offset = int64(r2)
			// Nothing may follow
			return
		}

corresponding type parameters have corresponding constraints.
</p>

<pre>
type Pair[A, B any] struct {
	a A
	b B
}

func (p Pair[A, B]) Swap() Pair[B, A]  { … }  // receiver declares A, B
func (p Pair[First, _]) First() First  { … }  // receiver declares First, corresponds to A in Pair
</pre>

<h2 id="Expressions">Expressions</h2>

<p>

// license that can be found in the LICENSE file.

package p4

type Pair[T1 interface{ M() }, T2 ~int] struct {
	f1 T1
	f2 T2
}

func NewPair[T1 interface{ M() }, T2 ~int](v1 T1, v2 T2) Pair[T1, T2] {
	return Pair[T1, T2]{f1: v1, f2: v2}
}

func (p Pair[X1, _]) First() X1 {
	return p.f1
}

func (p Pair[_, X2]) Second() X2 {
	return p.f2
}

// Deprecated: Use something else.

	CASPD	(R2, R3), (R2), (R9, R10)                        // ERROR "destination register pair must start from even register"
	CASPD	(R2, R4), (R2), (R8, R9)                         // ERROR "source register pair must be contiguous"
	CASPD	(R2, R3), (R2), (R8, R10)                        // ERROR "destination register pair must be contiguous"

				// both 1st operand and 3rd operand are (Rs, Rs+1) register pair.
				// And the register pair must be contiguous.
				if (a[0].Type != obj.TYPE_REGREG) || (a[2].Type != obj.TYPE_REGREG) {
					p.errorf("invalid addressing modes for 1st or 3rd operand to %s instruction, must be register pair", op)
					return
				}
				// For ARM64 CASP-like instructions, its 2nd destination operand is register pair(Rt, Rt+1) that can

		nsecs = -(nsecs - 1e9) // Take that second away from nsecs
	}
	return strings.TrimRight(fmt.Sprintf("%s%d.%09d", sign, secs, nsecs), "0")
}

// parsePAXRecord parses the input PAX record string into a key-value pair.
// If parsing is successful, it will slice off the currently read record and
// return the remainder as r.
func parsePAXRecord(s string) (k, v, r string, err error) {
	// The size field ends at the first space.

	MRS	ID_PFR1_EL1, R12                   // 2c0138d5
	MRS	ISR_EL1, R24                       // 18c138d5
	MRS	MAIR_EL1, R20                      // 14a238d5
	MSR	R21, MAIR_EL1                      // 15a218d5
	MRS	MAIR_EL1, R20                      // 14a238d5
	MSR	R5, MAIR_EL1                       // 05a218d5
	MRS	MDCCINT_EL1, R23                   // 170230d5
	MSR	R27, MDCCINT_EL1                   // 1b0210d5

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.
The environment variable `GODEBUG`
can hold a comma-separated list of these settings.
For example, if a Go program is running in an environment that contains

<code>[R0,g,R12-R15]</code>: For multi-register instructions, the set comprising
<code>R0</code>, <code>g</code>, and <code>R12</code> through <code>R15</code> inclusive.
</li>

<li>
<code>(R5, R6)</code>: Destination register pair.
</li>

</ul>

<h3 id="arm64">ARM64</h3>

<p>
<code>R18</code> is the "platform register", reserved on the Apple platform.
To prevent accidental misuse, the register is named <code>R18_PLATFORM</code>.