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Merged
PurHur merged 2 commits into from
May 20, 2026
Merged

Language: null coalescing operator (??) — closes #99 #334

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72ec99a
Implement null coalescing operator (??) for VM and lint pipeline.
PurHur May 20, 2026
4f805ca
Merge origin/master into issue-99-null-coalescing
PurHur May 20, 2026
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175 changes: 101 additions & 74 deletions docs/bootstrap-inventory.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,9 +8,9 @@ Regenerate: `php script/bootstrap-inventory.php`

| Metric | Count |
|--------|------:|
| PHP files on vm.php path | 212 |
| PHP files on vm.php path | 214 |
| Source constructs flagged (blockers) | 10 |
| Source constructs flagged (warnings) | 553 |
| Source constructs flagged (warnings) | 570 |

## Compiler CFG gaps (`lib/Compiler.php`)

Expand Down Expand Up @@ -162,7 +162,7 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
| `ext/types/strlen.php` | 0 | 1 |
| `lib/AOT/Linker.php` | 8 | 1 |
| `lib/Block.php` | 0 | 4 |
| `lib/Compiler.php` | 0 | 57 |
| `lib/Compiler.php` | 0 | 68 |
| `lib/Frame.php` | 0 | 1 |
| `lib/Func.php` | 0 | 1 |
| `lib/Func/Internal.php` | 0 | 2 |
Expand Down Expand Up @@ -199,6 +199,7 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
| `lib/JIT/Call.php` | 0 | 1 |
| `lib/JIT/Call/Native.php` | 0 | 1 |
| `lib/JIT/Call/Vararg.php` | 0 | 2 |
| `lib/JIT/CoalesceHelper.php` | 0 | 1 |
| `lib/JIT/Context.php` | 0 | 15 |
| `lib/JIT/HashTableHelper.php` | 0 | 1 |
| `lib/JIT/Helper.php` | 0 | 7 |
Expand All @@ -215,7 +216,8 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
| `lib/Lint/IncrementDetector.php` | 0 | 4 |
| `lib/Lint/Issue.php` | 0 | 2 |
| `lib/Lint/LintCompiler.php` | 0 | 6 |
| `lib/Lint/Linter.php` | 0 | 5 |
| `lib/Lint/Linter.php` | 0 | 6 |
| `lib/Lint/ListDestructuringDetector.php` | 0 | 4 |
| `lib/Lint/UnsupportedRegistry.php` | 0 | 1 |
| `lib/Module.php` | 0 | 1 |
| `lib/ModuleAbstract.php` | 0 | 1 |
Expand Down Expand Up @@ -1046,63 +1048,74 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
### `lib/Compiler.php`

**Warnings** (review for bootstrap subset):
- new Func\PHP (line 41)
- new Block (line 46)
- new OpCode (line 100)
- new Block (line 109)
- new OpCode (line 119)
- new Variable (line 134)
- new Operand\Temporary (line 135)
- new OpCode (line 157)
- new Operand\Literal (line 168)
- new OpCode (line 170)
- new OpCode (line 185)
- new OpCode (line 193)
- new OpCode (line 213)
- new OpCode (line 218)
- new OpCode (line 251)
- new OpCode (line 260)
- new OpCode (line 353)
- new OpCode (line 360)
- new OpCode (line 374)
- new OpCode (line 380)
- new OpCode (line 398)
- new OpCode (line 404)
- new OpCode (line 410)
- new OpCode (line 421)
- new OpCode (line 429)
- new OpCode (line 435)
- new OpCode (line 441)
- new OpCode (line 446)
- new OpCode (line 453)
- new OpCode (line 460)
- new OpCode (line 466)
- new OpCode (line 471)
- new OpCode (line 478)
- new OpCode (line 485)
- new OpCode (line 490)
- new OpCode (line 495)
- new OpCode (line 504)
- new OpCode (line 509)
- new OpCode (line 516)
- new OpCode (line 525)
- new OpCode (line 544)
- new Block (line 560)
- new Func\PHP (line 42)
- new Block (line 47)
- new OpCode (line 103)
- new Block (line 112)
- new OpCode (line 122)
- new Variable (line 137)
- new Operand\Temporary (line 138)
- new OpCode (line 160)
- new Operand\Literal (line 171)
- new OpCode (line 173)
- new OpCode (line 188)
- new OpCode (line 196)
- new OpCode (line 216)
- new OpCode (line 221)
- new OpCode (line 254)
- new OpCode (line 263)
- new OpCode (line 356)
- new OpCode (line 363)
- new OpCode (line 377)
- new OpCode (line 383)
- new OpCode (line 401)
- new OpCode (line 407)
- new OpCode (line 413)
- new OpCode (line 424)
- new OpCode (line 432)
- new OpCode (line 438)
- new OpCode (line 444)
- new OpCode (line 449)
- new OpCode (line 456)
- new OpCode (line 463)
- new OpCode (line 469)
- new OpCode (line 474)
- new OpCode (line 481)
- new OpCode (line 488)
- new OpCode (line 493)
- new OpCode (line 498)
- new OpCode (line 507)
- new OpCode (line 512)
- new OpCode (line 519)
- new OpCode (line 528)
- new OpCode (line 547)
- new Block (line 559)
- new Block (line 563)
- new OpCode (line 566)
- new OpCode (line 572)
- new OpCode (line 586)
- new Block (line 593)
- new OpCode (line 596)
- new OpCode (line 606)
- new Operand\Temporary (line 616)
- new Variable (line 624)
- new Operand\Temporary (line 626)
- new Variable (line 687)
- new OpCode (line 717)
- new OpCode (line 723)
- new OpCode (line 727)
- 25 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler
- new OpCode (line 567)
- new Block (line 574)
- new OpCode (line 582)
- new OpCode (line 589)
- new OpCode (line 597)
- new OpCode (line 603)
- new OpCode (line 611)
- new OpCode (line 614)
- new OpCode (line 620)
- new Block (line 674)
- new Block (line 677)
- new OpCode (line 680)
- new OpCode (line 686)
- new OpCode (line 700)
- new Block (line 707)
- new OpCode (line 710)
- new OpCode (line 720)
- new Temporary (line 730)
- new Variable (line 740)
- new Operand\Temporary (line 742)
- new Variable (line 803)
- new OpCode (line 833)
- new OpCode (line 839)
- new OpCode (line 843)
- 28 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/Frame.php`

Expand Down Expand Up @@ -1142,13 +1155,13 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
- new Variable (line 139)
- new JIT\Call\Vararg (line 146)
- new JIT\Call\Native (line 149)
- new ext\standard\boolval (line 249)
- new Variable (line 413)
- new Variable (line 734)
- new Operand\Literal (line 804)
- new Operand\Literal (line 808)
- new Operand\Literal (line 812)
- 11 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler
- new ext\standard\boolval (line 263)
- new Variable (line 427)
- new Variable (line 773)
- new Operand\Literal (line 843)
- new Operand\Literal (line 847)
- new Operand\Literal (line 851)
- 12 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/JIT/Analyzer.php`

Expand Down Expand Up @@ -1312,6 +1325,11 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
- 1 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler
- 1 closure(s)

### `lib/JIT/CoalesceHelper.php`

**Warnings** (review for bootstrap subset):
- 1 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/JIT/Context.php`

**Warnings** (review for bootstrap subset):
Expand Down Expand Up @@ -1450,11 +1468,20 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:

**Warnings** (review for bootstrap subset):
- new Runtime (line 24)
- new IncrementDetector (line 44)
- new State (line 86)
- new LintCompiler (line 101)
- new IncrementDetector (line 45)
- new ListDestructuringDetector (line 46)
- new State (line 89)
- new LintCompiler (line 104)
- 9 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/Lint/ListDestructuringDetector.php`

**Warnings** (review for bootstrap subset):
- new ParserFactory (line 27)
- new NodeTraverser (line 54)
- new Issue (line 61)
- 2 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/Lint/UnsupportedRegistry.php`

**Warnings** (review for bootstrap subset):
Expand Down Expand Up @@ -1510,10 +1537,10 @@ These `LogicException` messages indicate CFG ops or expressions not yet lowered:
**Warnings** (review for bootstrap subset):
- new Variable (line 64)
- new Variable (line 69)
- new Func\PHP (line 217)
- new ClassEntry (line 267)
- new ObjectEntry (line 279)
- new VM\ClassProperty (line 369)
- new Func\PHP (line 224)
- new ClassEntry (line 274)
- new ObjectEntry (line 286)
- new VM\ClassProperty (line 376)
- 3 class method(s) — PHPCfg Op\Stmt\ClassMethod not lowered in Compiler

### `lib/VM/ClassEntry.php`
Expand Down
1 change: 0 additions & 1 deletion docs/unsupported-syntax.md
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Expand Up @@ -19,7 +19,6 @@ Some constructs (for example destructuring assigns and prefix/postfix `++`/`--`)
| CFG kind | Tracking |
|----------|----------|
| `Stmt_Foreach` | [#53](https://github.com/PurHur/php-compiler/issues/53) |
| `Expr_BinaryOp_Coalesce` (`??`) | [#99](https://github.com/PurHur/php-compiler/issues/99) |
| `Expr_Throw`, `Stmt_Try`, `Stmt_Catch`, `Stmt_Finally` | [#195](https://github.com/PurHur/php-compiler/issues/195) |
| `Expr_Ternary` (`?:`) | [#114](https://github.com/PurHur/php-compiler/issues/114) |
| `Expr_AssignOp_*`, `Expr_BinaryOp_ShiftLeft` / `ShiftRight` (compound assign) | [#136](https://github.com/PurHur/php-compiler/issues/136) |
Expand Down
118 changes: 117 additions & 1 deletion lib/Compiler.php
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Expand Up @@ -14,6 +14,7 @@
use PHPCfg\Op;
use PHPCfg\Block as CfgBlock;
use PHPCfg\Operand;
use PHPCfg\Operand\Temporary;
use PHPCfg\Script;
use PHPTypes\Type;
use PHPCompiler\VM\Variable;
Expand Down Expand Up @@ -81,6 +82,8 @@ protected function compileOps(array $ops, Block $block): void {
default:
if ($child instanceof Op\Expr\Isset_ && count($child->vars) > 1) {
$block = $this->compileIssetMulti($child, $block);
} elseif ($child instanceof Op\Expr\BinaryOp\Coalesce) {
$block = $this->compileCoalesce($child, $block);
} else {
$this->compileOp($child, $block);
}
Expand Down Expand Up @@ -549,6 +552,117 @@ protected function compileIsset(Op\Expr\Isset_ $expr, Block $block): array
)];
}

protected function compileCoalesce(Op\Expr\BinaryOp\Coalesce $expr, Block $block): Block
{
$resultSlot = $this->compileOperand($expr->result, $block, false);

$endBlock = new Block($block->orig);
$endBlock->inheritUndefinedLocals = true;
$endBlock->inheritScopeFrom($block);

$rightBlock = new Block($block->orig);
$rightBlock->inheritUndefinedLocals = true;
$rightBlock->inheritScopeFrom($block);
$rightSlot = $this->compileOperand($expr->right, $rightBlock, true);
$rightBlock->addOpCode(new OpCode(
OpCode::TYPE_ASSIGN,
$resultSlot,
$resultSlot,
$rightSlot
));

$leftBlock = new Block($block->orig);
$leftBlock->inheritUndefinedLocals = true;
$leftBlock->inheritScopeFrom($block);

$checkSlot = $this->compileBoolTemporary($block);
$issetTarget = $this->resolveCoalesceIssetTarget($expr->left, $block);
if (null !== $issetTarget) {
[$containerSlot, $dimSlot] = $issetTarget;
$block->addOpCode(new OpCode(
OpCode::TYPE_ISSET,
$checkSlot,
$containerSlot,
$dimSlot
));
$leftSlot = $this->compileOperand($expr->left, $leftBlock, true);
$leftBlock->addOpCode(new OpCode(
OpCode::TYPE_ASSIGN,
$resultSlot,
$resultSlot,
$leftSlot
));
} else {
$leftSlot = $this->compileOperand($expr->left, $block, true);
$block->addOpCode(new OpCode(
OpCode::TYPE_ASSIGN,
$resultSlot,
$resultSlot,
$leftSlot
));
$block->addOpCode(new OpCode(
OpCode::TYPE_ISSET,
$checkSlot,
$leftSlot,
null
));
}

$leftJump = new OpCode(OpCode::TYPE_JUMP);
$leftJump->block1 = $endBlock;
$leftBlock->addOpCode($leftJump);
$rightJump = new OpCode(OpCode::TYPE_JUMP);
$rightJump->block1 = $endBlock;
$rightBlock->addOpCode($rightJump);
$endBlock->parents[] = $leftBlock;
$endBlock->parents[] = $rightBlock;

$coalesceOp = new OpCode(
OpCode::TYPE_COALESCE,
$resultSlot,
$checkSlot
);
$coalesceOp->block1 = $leftBlock;
$coalesceOp->block2 = $rightBlock;
$coalesceOp->block3 = $endBlock;
$block->addOpCode($coalesceOp);

return $endBlock;
}

/**
* @return ?array{0: int, 1: ?int}
*/
protected function resolveCoalesceIssetTarget(Operand $operand, Block $block): ?array
{
if (null !== $this->unwrapArrayDimFetch($operand)) {
return $this->resolveIssetTarget($operand, $block);
}
if (null !== $this->unwrapVariableOperand($operand)) {
return $this->resolveIssetTarget($operand, $block);
}

return null;
}

protected function unwrapVariableOperand(Operand $operand): ?Operand\Variable
{
while ($operand instanceof Temporary) {
if ($operand->original instanceof Operand\Variable) {
return $operand->original;
}
if (null === $operand->original) {
return null;
}
$operand = $operand->original;
}
if ($operand instanceof Operand\Variable) {
return $operand;
}

return null;
}

/**
* isset($a, $b, …) with short-circuit evaluation (PHP semantics).
* Returns the block where compilation should continue.
Expand Down Expand Up @@ -613,8 +727,10 @@ protected function compileIssetMulti(Op\Expr\Isset_ $expr, Block $block): Block

protected function compileBoolTemporary(Block $block): int
{
$operand = new Operand\Temporary;
$operand = new Temporary;
$operand->type = Type::bool();
// JIT assignOperandValue skips operands with empty usages (#99 coalesce branches).
$operand->usages[] = $operand;

return $block->getVarSlot($operand, false);
}
Expand Down
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