Skip to content

Add fast path to TypeCombinator::union() for trivial 2-type cases #5325

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
ondrejmirtes merged 3 commits into from
Apr 1, 2026
Merged

Add fast path to TypeCombinator::union() for trivial 2-type cases #5325

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
1332c41
autoresearch: TypeCombinator::union fast path for never/mixed/identit…
SanderMuller Mar 28, 2026
8566e8d
Add benchmark for TypeCombinator::union fast path
SanderMuller Mar 29, 2026
fe1df1a
TypeCombinator::union optimization in case of many `*NEVER*`
ondrejmirtes Apr 1, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
82 changes: 82 additions & 0 deletions src/Type/TypeCombinator.php
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,88 @@
return new NeverType();
}

// Fast path for single non-union type
if ($typesCount === 1) {
$singleType = $types[0];
if (!$singleType instanceof UnionType && !$singleType->isArray()->yes()) {

Check warning on line 159 in src/Type/TypeCombinator.php

View workflow job for this annotation

GitHub Actions / Mutation Testing (8.4, ubuntu-latest) 

Escaped Mutant for Mutator "PHPStan\Infection\TrinaryLogicMutator":

@@ @@
 		// Fast path for single non-union type
 		if ($typesCount === 1) {
 			$singleType = $types[0];
-			if (!$singleType instanceof UnionType && !$singleType->isArray()->yes()) {
+			if (!$singleType instanceof UnionType && $singleType->isArray()->no()) {
 				return $singleType;
 			}
 		}

Check warning on line 159 in src/Type/TypeCombinator.php

View workflow job for this annotation

GitHub Actions / Mutation Testing (8.3, ubuntu-latest) 

Escaped Mutant for Mutator "PHPStan\Infection\TrinaryLogicMutator":

@@ @@
 		// Fast path for single non-union type
 		if ($typesCount === 1) {
 			$singleType = $types[0];
-			if (!$singleType instanceof UnionType && !$singleType->isArray()->yes()) {
+			if (!$singleType instanceof UnionType && $singleType->isArray()->no()) {
 				return $singleType;
 			}
 		}
return $singleType;
}
}

// Fast path for common 2-type cases
if ($typesCount === 2) {
$a = $types[0];
$b = $types[1];

// union(never, X) = X and union(X, never) = X
if ($a instanceof NeverType && !$a->isExplicit()) {
return $b;
}
if ($b instanceof NeverType && !$b->isExplicit()) {
return $a;
}

// union(mixed, X) = mixed (non-explicit, non-template, no subtracted)
if ($a instanceof MixedType && !$a->isExplicitMixed() && !$a instanceof TemplateMixedType && $a->getSubtractedType() === null) {
return $a;
}
if ($b instanceof MixedType && !$b->isExplicitMixed() && !$b instanceof TemplateMixedType && $b->getSubtractedType() === null) {
return $b;
}

// union(X, X) = X (same object identity)
if ($a === $b) {
return $a;
}
}

// Fast path for N>2: strip implicit NeverTypes and short-circuit on mixed
if ($typesCount > 2) {
$neverCount = 0;
$hasUnionOrBenevolent = false;
for ($i = 0; $i < $typesCount; $i++) {
$t = $types[$i];
if (
$t instanceof MixedType
&& !$t->isExplicitMixed()
&& !$t instanceof TemplateMixedType
&& $t->getSubtractedType() === null
) {
return $t;
}
if ($t instanceof NeverType && !$t->isExplicit()) {
$neverCount++;
} elseif ($t instanceof UnionType && !$t instanceof TemplateType) {
$hasUnionOrBenevolent = true;
}
}

if ($neverCount > 0 && !$hasUnionOrBenevolent) {
if ($neverCount === $typesCount) {
return new NeverType();
}

$filtered = [];
for ($i = 0; $i < $typesCount; $i++) {
if ($types[$i] instanceof NeverType && !$types[$i]->isExplicit()) {
continue;
}

$filtered[] = $types[$i];
}
$filteredCount = count($filtered);

if ($filteredCount === 1 && !$filtered[0]->isArray()->yes()) {

Check warning on line 227 in src/Type/TypeCombinator.php

View workflow job for this annotation

GitHub Actions / Mutation Testing (8.4, ubuntu-latest) 

Escaped Mutant for Mutator "PHPStan\Infection\TrinaryLogicMutator":

@@ @@
 				}
 				$filteredCount = count($filtered);
 
-				if ($filteredCount === 1 && !$filtered[0]->isArray()->yes()) {
+				if ($filteredCount === 1 && $filtered[0]->isArray()->no()) {
 					return $filtered[0];
 				}
 				if ($filteredCount === 2) {

Check warning on line 227 in src/Type/TypeCombinator.php

View workflow job for this annotation

GitHub Actions / Mutation Testing (8.3, ubuntu-latest) 

Escaped Mutant for Mutator "PHPStan\Infection\TrinaryLogicMutator":

@@ @@
 				}
 				$filteredCount = count($filtered);
 
-				if ($filteredCount === 1 && !$filtered[0]->isArray()->yes()) {
+				if ($filteredCount === 1 && $filtered[0]->isArray()->no()) {
 					return $filtered[0];
 				}
 				if ($filteredCount === 2) {
return $filtered[0];
}
if ($filteredCount === 2) {
return self::union($filtered[0], $filtered[1]);
}
$types = $filtered;
$typesCount = $filteredCount;
}
}

$alreadyNormalized = [];
$alreadyNormalizedCounter = 0;

Expand Down
211 changes: 211 additions & 0 deletions tests/bench/data/union-fast-path.php
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,211 @@
<?php

namespace UnionFastPath;

/**
* Exercises TypeCombinator::union() fast path for trivial 2-type cases.
*
* Each early-return branch produces union(never, X) during scope merging.
* Each if/else with unchanged variables produces union(X, X).
* The many mixed parameters produce union(mixed, X) during narrowing.
*/

/** @param array<string, mixed> $d */
function narrowAndBranch(array $d, mixed $m1, mixed $m2, mixed $m3, mixed $m4): string
{
if (!is_string($m1)) { return ''; }
if (!is_string($m2)) { return ''; }
if (!is_string($m3)) { return ''; }
if (!is_string($m4)) { return ''; }

$a = $b = $c = $d1 = $e = $f = $g = $h = '';

if (isset($d['a'])) { $a = (string) $d['a']; } else { return ''; }
if (isset($d['b'])) { $b = (string) $d['b']; } else { return ''; }
if (isset($d['c'])) { $c = (string) $d['c']; } else { return ''; }
if (isset($d['d'])) { $d1 = (string) $d['d']; } else { return ''; }
if (isset($d['e'])) { $e = (string) $d['e']; } else { return ''; }
if (isset($d['f'])) { $f = (string) $d['f']; } else { return ''; }
if (isset($d['g'])) { $g = (string) $d['g']; } else { return ''; }
if (isset($d['h'])) { $h = (string) $d['h']; } else { return ''; }

return $a . $b . $c . $d1 . $e . $f . $g . $h . $m1 . $m2 . $m3 . $m4;
}

/** @param array<string, mixed> $d */
function narrowAndBranch2(array $d, mixed $m1, mixed $m2, mixed $m3, mixed $m4): string
{
if (!is_string($m1)) { return ''; }
if (!is_string($m2)) { return ''; }
if (!is_string($m3)) { return ''; }
if (!is_string($m4)) { return ''; }

$a = $b = $c = $d1 = $e = $f = $g = $h = '';

if (isset($d['a1'])) { $a = (string) $d['a1']; } else { return ''; }
if (isset($d['b1'])) { $b = (string) $d['b1']; } else { return ''; }
if (isset($d['c1'])) { $c = (string) $d['c1']; } else { return ''; }
if (isset($d['d1'])) { $d1 = (string) $d['d1']; } else { return ''; }
if (isset($d['e1'])) { $e = (string) $d['e1']; } else { return ''; }
if (isset($d['f1'])) { $f = (string) $d['f1']; } else { return ''; }
if (isset($d['g1'])) { $g = (string) $d['g1']; } else { return ''; }
if (isset($d['h1'])) { $h = (string) $d['h1']; } else { return ''; }

return $a . $b . $c . $d1 . $e . $f . $g . $h . $m1 . $m2 . $m3 . $m4;
}

/** @param array<string, mixed> $d */
function narrowAndBranch3(array $d, mixed $m1, mixed $m2, mixed $m3, mixed $m4): string
{
if (!is_string($m1)) { return ''; }
if (!is_string($m2)) { return ''; }
if (!is_string($m3)) { return ''; }
if (!is_string($m4)) { return ''; }

$a = $b = $c = $d1 = $e = $f = $g = $h = '';

if (isset($d['a2'])) { $a = (string) $d['a2']; } else { return ''; }
if (isset($d['b2'])) { $b = (string) $d['b2']; } else { return ''; }
if (isset($d['c2'])) { $c = (string) $d['c2']; } else { return ''; }
if (isset($d['d2'])) { $d1 = (string) $d['d2']; } else { return ''; }
if (isset($d['e2'])) { $e = (string) $d['e2']; } else { return ''; }
if (isset($d['f2'])) { $f = (string) $d['f2']; } else { return ''; }
if (isset($d['g2'])) { $g = (string) $d['g2']; } else { return ''; }
if (isset($d['h2'])) { $h = (string) $d['h2']; } else { return ''; }

return $a . $b . $c . $d1 . $e . $f . $g . $h . $m1 . $m2 . $m3 . $m4;
}

/** @param array<string, mixed> $d */
function narrowAndBranch4(array $d, mixed $m1, mixed $m2, mixed $m3, mixed $m4): string
{
if (!is_string($m1)) { return ''; }
if (!is_string($m2)) { return ''; }
if (!is_string($m3)) { return ''; }
if (!is_string($m4)) { return ''; }

$a = $b = $c = $d1 = $e = $f = $g = $h = '';

if (isset($d['a3'])) { $a = (string) $d['a3']; } else { return ''; }
if (isset($d['b3'])) { $b = (string) $d['b3']; } else { return ''; }
if (isset($d['c3'])) { $c = (string) $d['c3']; } else { return ''; }
if (isset($d['d3'])) { $d1 = (string) $d['d3']; } else { return ''; }
if (isset($d['e3'])) { $e = (string) $d['e3']; } else { return ''; }
if (isset($d['f3'])) { $f = (string) $d['f3']; } else { return ''; }
if (isset($d['g3'])) { $g = (string) $d['g3']; } else { return ''; }
if (isset($d['h3'])) { $h = (string) $d['h3']; } else { return ''; }

return $a . $b . $c . $d1 . $e . $f . $g . $h . $m1 . $m2 . $m3 . $m4;
}

/** @param array<string, mixed> $d */
function narrowAndBranch5(array $d, mixed $m1, mixed $m2, mixed $m3, mixed $m4): string
{
if (!is_string($m1)) { return ''; }
if (!is_string($m2)) { return ''; }
if (!is_string($m3)) { return ''; }
if (!is_string($m4)) { return ''; }

$a = $b = $c = $d1 = $e = $f = $g = $h = '';

if (isset($d['a4'])) { $a = (string) $d['a4']; } else { return ''; }
if (isset($d['b4'])) { $b = (string) $d['b4']; } else { return ''; }
if (isset($d['c4'])) { $c = (string) $d['c4']; } else { return ''; }
if (isset($d['d4'])) { $d1 = (string) $d['d4']; } else { return ''; }
if (isset($d['e4'])) { $e = (string) $d['e4']; } else { return ''; }
if (isset($d['f4'])) { $f = (string) $d['f4']; } else { return ''; }
if (isset($d['g4'])) { $g = (string) $d['g4']; } else { return ''; }
if (isset($d['h4'])) { $h = (string) $d['h4']; } else { return ''; }

return $a . $b . $c . $d1 . $e . $f . $g . $h . $m1 . $m2 . $m3 . $m4;
}

function deepSwitch(mixed $val, mixed $a, mixed $b, mixed $c, mixed $d, mixed $e, mixed $f): string
{
if (!is_string($a)) { return ''; }
if (!is_string($b)) { return ''; }
if (!is_string($c)) { return ''; }
if (!is_string($d)) { return ''; }
if (!is_string($e)) { return ''; }
if (!is_string($f)) { return ''; }

$r = '';
if ($val === 'x1') { $r = $a; }
elseif ($val === 'x2') { $r = $b; }
elseif ($val === 'x3') { $r = $c; }
elseif ($val === 'x4') { $r = $d; }
elseif ($val === 'x5') { $r = $e; }
elseif ($val === 'x6') { $r = $f; }
elseif ($val === 'x7') { $r = $a . $b; }
elseif ($val === 'x8') { $r = $c . $d; }
elseif ($val === 'x9') { $r = $e . $f; }
elseif ($val === 'x10') { $r = $a . $c; }
elseif ($val === 'x11') { $r = $b . $d; }
elseif ($val === 'x12') { $r = $c . $e; }
elseif ($val === 'x13') { $r = $d . $f; }
elseif ($val === 'x14') { $r = $a . $e; }
elseif ($val === 'x15') { $r = $b . $f; }
else { $r = $a . $b . $c . $d . $e . $f; }

return $r;
}

function deepSwitch2(mixed $val, mixed $a, mixed $b, mixed $c, mixed $d, mixed $e, mixed $f): string
{
if (!is_string($a)) { return ''; }
if (!is_string($b)) { return ''; }
if (!is_string($c)) { return ''; }
if (!is_string($d)) { return ''; }
if (!is_string($e)) { return ''; }
if (!is_string($f)) { return ''; }

$r = '';
if ($val === 'y1') { $r = $a; }
elseif ($val === 'y2') { $r = $b; }
elseif ($val === 'y3') { $r = $c; }
elseif ($val === 'y4') { $r = $d; }
elseif ($val === 'y5') { $r = $e; }
elseif ($val === 'y6') { $r = $f; }
elseif ($val === 'y7') { $r = $a . $b; }
elseif ($val === 'y8') { $r = $c . $d; }
elseif ($val === 'y9') { $r = $e . $f; }
elseif ($val === 'y10') { $r = $a . $c; }
elseif ($val === 'y11') { $r = $b . $d; }
elseif ($val === 'y12') { $r = $c . $e; }
elseif ($val === 'y13') { $r = $d . $f; }
elseif ($val === 'y14') { $r = $a . $e; }
elseif ($val === 'y15') { $r = $b . $f; }
else { $r = $a . $b . $c . $d . $e . $f; }

return $r;
}

function deepSwitch3(mixed $val, mixed $a, mixed $b, mixed $c, mixed $d, mixed $e, mixed $f): string
{
if (!is_string($a)) { return ''; }
if (!is_string($b)) { return ''; }
if (!is_string($c)) { return ''; }
if (!is_string($d)) { return ''; }
if (!is_string($e)) { return ''; }
if (!is_string($f)) { return ''; }

$r = '';
if ($val === 'z1') { $r = $a; }
elseif ($val === 'z2') { $r = $b; }
elseif ($val === 'z3') { $r = $c; }
elseif ($val === 'z4') { $r = $d; }
elseif ($val === 'z5') { $r = $e; }
elseif ($val === 'z6') { $r = $f; }
elseif ($val === 'z7') { $r = $a . $b; }
elseif ($val === 'z8') { $r = $c . $d; }
elseif ($val === 'z9') { $r = $e . $f; }
elseif ($val === 'z10') { $r = $a . $c; }
elseif ($val === 'z11') { $r = $b . $d; }
elseif ($val === 'z12') { $r = $c . $e; }
elseif ($val === 'z13') { $r = $d . $f; }
elseif ($val === 'z14') { $r = $a . $e; }
elseif ($val === 'z15') { $r = $b . $f; }
else { $r = $a . $b . $c . $d . $e . $f; }

return $r;
}
Loading