Infer closure parameter types in pipe operator

Author: ondrejmirtes

src/Parser/ArrowFunctionPipeVisitor.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use Override;
+use PhpParser\Node;
+use PhpParser\NodeVisitorAbstract;
+use PHPStan\DependencyInjection\AutowiredService;
+
+#[AutowiredService]
+final class ArrowFunctionPipeVisitor extends NodeVisitorAbstract
+{
+
+	#[Override]
+	public function enterNode(Node $node): ?Node
+	{
+		if (!$node instanceof Node\Expr\BinaryOp\Pipe) {
+			return null;
+		}
+
+		if (!$node->right instanceof Node\Expr\ArrowFunction) {
+			return null;
+		}
+
+		$node->right->setAttribute(ArrowFunctionArgVisitor::ATTRIBUTE_NAME, [
+			new Node\Arg($node->left),
+		]);
+
+		return null;
+	}
+
+}

src/Parser/ClosurePipeVisitor.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Parser;
+
+use Override;
+use PhpParser\Node;
+use PhpParser\NodeVisitorAbstract;
+use PHPStan\DependencyInjection\AutowiredService;
+
+#[AutowiredService]
+final class ClosurePipeVisitor extends NodeVisitorAbstract
+{
+
+	#[Override]
+	public function enterNode(Node $node): ?Node
+	{
+		if (!$node instanceof Node\Expr\BinaryOp\Pipe) {
+			return null;
+		}
+
+		if (!$node->right instanceof Node\Expr\Closure) {
+			return null;
+		}
+
+		$node->right->setAttribute(ClosureArgVisitor::ATTRIBUTE_NAME, [
+			new Node\Arg($node->left),
+		]);
+
+		return null;
+	}
+
+}

tests/PHPStan/Analyser/nsrt/pipe-operator.php

@@ -34,6 +34,9 @@ public function doBar(): void
 
 }
 
+/**
+ * @return positive-int
+ */
 function doFoo(): int
 {
 
@@ -44,8 +47,38 @@ class FunctionFoo
 
 	public function doBar(): void
 	{
-		assertType('int', 'foo' |> doFoo(...));
-		assertType('int', 'foo' |> 'PipeOperatorTypes\\doFoo');
+		assertType('int<1, max>', 'foo' |> doFoo(...));
+		assertType('int<1, max>', 'foo' |> 'PipeOperatorTypes\\doFoo');
+	}
+
+	public function doBaz(): void
+	{
+		doFoo() |> function ($x) {
+			assertType('int<1, max>', $x);
+		};
+
+		doFoo() |> fn ($x) => assertType('int<1, max>', $x);
+
+		doFoo() |> function (int $x) {
+			assertType('int<1, max>', $x);
+		};
+
+		doFoo() |> fn (int $x) => assertType('int<1, max>', $x);
+	}
+
+	public function doBaz2(): void
+	{
+		(function ($x) {
+			assertType('int<1, max>', $x);
+		})(doFoo());
+
+		(fn ($x) => assertType('int<1, max>', $x))(doFoo());
+
+		(function (int $x) {
+			assertType('int<1, max>', $x);
+		})(doFoo());
+
+		(fn (int $x) => assertType('int<1, max>', $x))(doFoo());
 	}
 
 }