inline

@deprecatedInheritance("Scheduled for being final in the future", "2.13.0")
class inline extends StaticAnnotation

An annotation for methods that the optimizer should inline.

Note that by default, the Scala optimizer is disabled and no callsites are inlined. See -opt:help for information on how to enable the optimizer and inliner.

When inlining is enabled, the inliner will always try to inline methods or callsites annotated @inline (under the condition that inlining from the defining class is allowed, see -opt-inline-from:help). If inlining is not possible, for example because the method is not final, an optimizer warning will be issued. See -opt-warnings:help for details.

Examples:

@inline   final def f1(x: Int) = x
@noinline final def f2(x: Int) = x
         final def f3(x: Int) = x

def t1 = f1(1)              // inlined if possible
def t2 = f2(1)              // not inlined
def t3 = f3(1)              // may be inlined (the inliner heuristics can select the callsite)
def t4 = f1(1): @noinline   // not inlined (override at callsite)
def t5 = f2(1): @inline     // inlined if possible (override at callsite)
def t6 = f3(1): @inline     // inlined if possible
def t7 = f3(1): @noinline   // not inlined
}

Note: parentheses are required when annotating a callsite within a larger expression.

def t1 = f1(1) + f1(1): @noinline   // equivalent to (f1(1) + f1(1)): @noinline
def t2 = f1(1) + (f1(1): @noinline) // the second call to f1 is not inlined
Source
inline.scala
class Object
trait Matchable
class Any