Extensions POC

[thekid]

Extensions for any type, including primitives.

Definition

This is what we might parse this from as an idea:

abstract class StringExtensions {
  extension(string) {
    public function length(string $self) => strlen($self);
    public function contains(string $self, string $needle) => false !== strpos($self, $needle);
  }
}

Usage

Single-expression methods are inlined:

$test= "Test";        // Type inferred to string
$test->length();      // emitted inline as: strlen($test) 
$test->contains('e'); // emitted inline as: false !== strpos($test, 'e')

Performance

Obviously, tracking types will mean extra effort.

# Before
Test cases:  1071 succeeded, 9 skipped
Memory used: 12519.15 kB (12573.42 kB peak)
Time taken:  0.294 seconds (0.778 seconds overall)

# After (w/o the "ExtensionsTest" class)
Test cases:  1071 succeeded, 9 skipped
Memory used: 12534.26 kB (12588.54 kB peak)
Time taken:  0.304 seconds (0.793 seconds overall)

See also

• https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/extension
• Typed local variables #154 - we might benefit from this where we cannot easily infer the type
• Refactor function scopes: Capturing and returning ast#61 - function scopes and expressions vs. body