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fix(compiler): infer static return type for uniform match expressions #169

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fix(compiler): infer static return type for uniform match expressions
prateekbhujel Oct 15, 2026
6a62c2d
test(compiler): use portable integer literal suffix matching in Match…
prateekbhujel Oct 15, 2026
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59 changes: 59 additions & 0 deletions phpunit/code/match-expression-codegen.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
<?php
/**
* This file is part of TypePHP(AOT).
*
* @link https://www.swoole.com/aot/
* @contact service@swoole.com
*/

function testUniformIntMatch(int $x): int
{
return match ($x) {
1 => 10,
2 => 20,
default => 30,
};
}

function testUniformStringMatch(int $x): string
{
return match ($x) {
1 => 'first',
2 => 'second',
default => 'other',
};
}

function testMatchWithThrow(int $x): int
{
return match ($x) {
1 => 10,
2 => 20,
default => throw new \RuntimeException('Invalid choice'),
};
}

function testMatchNoDefault(int $x): int
{
return match ($x) {
1 => 100,
2 => 200,
};
}

function testMixedTypeMatch(int $x): mixed
{
return match ($x) {
1 => 10,
default => 'other',
};
}

function testMatchLocalVariableAssignment(int $x): void
{
$result = match ($x) {
1 => 10,
default => 20,
};
var_dump($result);
}
112 changes: 112 additions & 0 deletions phpunit/src/MatchExpressionCodegenTest.php
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@@ -0,0 +1,112 @@
<?php
/**
* This file is part of TypePHP(AOT).
*
* @link https://www.swoole.com/aot/
* @contact service@swoole.com
*/

use TypePhp\CompilerTest;

/**
* @internal
* @coversNothing
*/
final class MatchExpressionCodegenTest extends \BaseTest
{
private string $generatedCode;

protected function setUp(): void
{
parent::setUp();

global $translator;
$compiler = CompilerTest::create(TYPEPHP_ROOT_PATH);
$translator = $compiler;
$source = TYPEPHP_ROOT_PATH . '/phpunit/code/match-expression-codegen.php';
$compiler->addFiles([$source]);
$compiler->prepareFile($source);
$code = file_get_contents($compiler->convertFile($source));
self::assertIsString($code);
$this->generatedCode = $code;
}

public function testUniformIntMatchInfersIntAndAvoidsRuntimeReturnTypeCheck(): void
{
// Must emit typed lambda returning php::Int
self::assertStringContainsString('php_testuniformintmatch', $this->generatedCode);
self::assertStringContainsString('[&]() -> php::Int {', $this->generatedCode);

// Function body must not use php::Var temporary or throwReturnTypeError for uniform int match
$fnCode = $this->extractFunction('php_testuniformintmatch');
self::assertStringNotContainsString('php::Var', $fnCode);
self::assertStringNotContainsString('php::throwReturnTypeError', $fnCode);
self::assertMatchesRegularExpression('/return 10L{1,2};/', $fnCode);
self::assertMatchesRegularExpression('/return 20L{1,2};/', $fnCode);
self::assertMatchesRegularExpression('/return 30L{1,2};/', $fnCode);
}

public function testUniformStringMatchInfersString(): void
{
self::assertStringContainsString('php_testuniformstringmatch', $this->generatedCode);
$fnCode = $this->extractFunction('php_testuniformstringmatch');
self::assertStringContainsString('[&]() -> php::Str {', $fnCode);
self::assertStringNotContainsString('php::Var', $fnCode);
self::assertStringNotContainsString('php::throwReturnTypeError', $fnCode);
}

public function testMatchWithThrowArmPreservesInferredReturnType(): void
{
$fnCode = $this->extractFunction('php_testmatchwiththrow');
self::assertStringContainsString('[&]() -> php::Int {', $fnCode);
self::assertStringContainsString('php::throwException(', $fnCode);
self::assertStringContainsString('return {};', $fnCode);
}

public function testMatchNoDefaultEmitsTypedUnhandledMatchCase(): void
{
$fnCode = $this->extractFunction('php_testmatchnodefault');
self::assertStringContainsString('[&]() -> php::Int {', $fnCode);
self::assertStringContainsString('php::throwException("UnhandledMatchError", "Unhandled match case");', $fnCode);
self::assertStringContainsString('return {};', $fnCode);
}

public function testMixedTypeMatchFallsBackToVariant(): void
{
$fnCode = $this->extractFunction('php_testmixedtypematch');
self::assertStringContainsString('[&]() -> php::Var {', $fnCode);
self::assertStringContainsString('php::Var tmp_var_', $fnCode);
}

public function testMatchExpressionLocalVariableAssignment(): void
{
$fnCode = $this->extractFunction('php_testmatchlocalvariableassignment');
// $result must be inferred as php::Int rather than php::Var
self::assertStringContainsString('php::Int result = 0;', $fnCode);
self::assertStringNotContainsString('php::Var result;', $fnCode);
}

private function extractFunction(string $name): string
{
$pos = strpos($this->generatedCode, $name);
self::assertNotFalse($pos, "Function {$name} not found in generated code");
$braceStart = strpos($this->generatedCode, '{', $pos);
self::assertNotFalse($braceStart);

$depth = 0;
$len = strlen($this->generatedCode);
for ($i = $braceStart; $i < $len; $i++) {
$char = $this->generatedCode[$i];
if ($char === '{') {
$depth++;
} elseif ($char === '}') {
$depth--;
if ($depth === 0) {
return substr($this->generatedCode, $pos, $i - $pos + 1);
}
}
}

return substr($this->generatedCode, $pos, 1000);
}
}
19 changes: 19 additions & 0 deletions src/CompilerBase.php
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Original file line number Diff line number Diff line change
Expand Up @@ -3551,6 +3551,25 @@ protected function detectTypeOfExpr($expr): string
: $this->detectTypeOfExpr($expr->if);
$elseType = $this->detectTypeOfExpr($expr->else);
return $ifType === $elseType ? $ifType : Type::VAR;
case 'Expr_Match':
if (empty($expr->arms)) {
return Type::VAR;
}
$armTypes = [];
foreach ($expr->arms as $arm) {
if ($arm->body instanceof Expr\Throw_) {
continue;
}
$armTypes[] = Type::getReferencedType($this->detectTypeOfExpr($arm->body));
}
if (empty($armTypes)) {
return Type::VAR;
}
$uniqueTypes = array_unique($armTypes);
if (count($uniqueTypes) === 1) {
return reset($uniqueTypes);
}
return Type::VAR;
case 'Expr_BinaryOp_Plus':
case 'Expr_BinaryOp_Minus':
case 'Expr_BinaryOp_Mul':
Expand Down
46 changes: 35 additions & 11 deletions src/Parser/SelectionExpressionTrait.php
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Expand Up @@ -143,9 +143,13 @@ protected function parseMatch(Expr\Match_ $expr): string
$nativeSelection = $this->isNativeObjectClass($nativeClass);
$conditionNativeClass = $this->detectClassOfExpr($expr->cond);
$nativeCondition = $this->isNativeObjectClass($conditionNativeClass);
$returnType = $nativeSelection
? $this->getNativeObjectPointerType($nativeClass)
: Type::VAR;
if ($nativeSelection) {
$returnType = $this->getNativeObjectPointerType($nativeClass);
} else {
$inferredType = $this->detectTypeOfExpr($expr);
$returnType = $this->getNormalAssignType($inferredType);
}
$expr->setAttribute(self::ATTR_LOWERED_TYPE, $returnType);
$this->assertExprCanBeUsedAsValue($expr->cond, 'match condition');
$var = $this->parseIdentifier($expr->cond);
if ($this->isVarExpr($expr->cond)) {
Expand Down Expand Up @@ -220,24 +224,29 @@ protected function parseMatch(Expr\Match_ $expr): string
}
$code .= $this->getIndent() . 'if (' . $matched . ') {' . PHP_EOL;
$this->indentLevel++;
$code .= $this->formatMatchReturn($arm->body, $nativeClass);
$code .= $this->formatMatchReturn($arm->body, $nativeClass, $returnType);
$this->indentLevel--;
$code .= $this->getIndent() . '}' . PHP_EOL;
}

if ($default) {
$code .= $this->getIndent() . '{' . PHP_EOL;
$this->indentLevel++;
$code .= $this->formatMatchReturn($default, $nativeClass);
$code .= $this->formatMatchReturn($default, $nativeClass, $returnType);
$this->indentLevel--;
$code .= $this->getIndent() . '}' . PHP_EOL;
} else {
$code .= $this->getIndent() . '{' . PHP_EOL;
$this->indentLevel++;
$code .= $nativeSelection
? $this->getIndent() . 'php::throwException("UnhandledMatchError", "Unhandled match case");' . PHP_EOL
. $this->getIndent() . 'return nullptr;' . PHP_EOL
: $this->getIndent() . 'return php::throwException("UnhandledMatchError", "Unhandled match case");' . PHP_EOL;
if ($nativeSelection) {
$code .= $this->getIndent() . 'php::throwException("UnhandledMatchError", "Unhandled match case");' . PHP_EOL
. $this->getIndent() . 'return nullptr;' . PHP_EOL;
} elseif ($returnType === Type::VAR) {
$code .= $this->getIndent() . 'return php::throwException("UnhandledMatchError", "Unhandled match case");' . PHP_EOL;
} else {
$code .= $this->getIndent() . 'php::throwException("UnhandledMatchError", "Unhandled match case");' . PHP_EOL
. $this->getIndent() . 'return {};' . PHP_EOL;
}
$this->indentLevel--;
$code .= $this->getIndent() . '}' . PHP_EOL;
}
Expand All @@ -247,9 +256,24 @@ protected function parseMatch(Expr\Match_ $expr): string
return $code;
}

protected function formatMatchReturn(NodeAbstract $body, string $nativeClass = ''): string
protected function formatMatchReturn(NodeAbstract $body, string $nativeClass = '', string $returnType = Type::VAR): string
{
$this->assertExprCanBeUsedAsValue($body, 'match arm');
if ($body instanceof Expr\Throw_) {
[$value, $beforeStmts, $afterStmts] = $this->parseExprWithCapturedStmts($body);
$code = $this->formatCapturedStmtLines($beforeStmts);
$code .= $this->formatCapturedStmtLines($afterStmts);
if ($nativeClass !== '') {
$code .= $this->getIndent() . $value . ';' . PHP_EOL;
$code .= $this->getIndent() . 'return nullptr;' . PHP_EOL;
} elseif ($returnType === Type::VAR) {
$code .= $this->getIndent() . 'return ' . $value . ';' . PHP_EOL;
} else {
$code .= $this->getIndent() . $value . ';' . PHP_EOL;
$code .= $this->getIndent() . 'return {};' . PHP_EOL;
}
return $code;
}
[$value, $beforeStmts, $afterStmts] = $this->parseExprWithCapturedStmts($body);
if ($nativeClass !== '' && $this->isNull($body)) {
$value = 'nullptr';
Expand All @@ -261,7 +285,7 @@ protected function formatMatchReturn(NodeAbstract $body, string $nativeClass = '
$this->addLocalVar($tmpVar, $this->getNativeObjectPointerType($nativeClass));
$this->addNativeObject($tmpVar, $nativeClass);
} else {
$tmpVar = $this->addTmpVar(Type::VAR);
$tmpVar = $this->addTmpVar($returnType);
}
$code .= $this->getIndent() . "{$tmpVar} = {$value};" . PHP_EOL;
$code .= $this->formatCapturedStmtLines($afterStmts);
Expand Down
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