From a862bcdbcf5263cdaa78575554cfcd08f773e043 Mon Sep 17 00:00:00 2001
From: Markus Staab <m.staab@complex-it.de>
Date: Sun, 27 Mar 2022 21:05:56 +0200
Subject: [PATCH] infer non-empty-string on substr() comparison with constant
 string

---
 src/Analyser/TypeSpecifier.php                | 19 +++++++
 .../Analyser/NodeScopeResolverTest.php        |  1 +
 .../non-empty-string-substr-specifying.php    | 56 +++++++++++++++++++
 3 files changed, 76 insertions(+)
 create mode 100644 tests/PHPStan/Analyser/data/non-empty-string-substr-specifying.php

diff --git a/src/Analyser/TypeSpecifier.php b/src/Analyser/TypeSpecifier.php
index da3cbca409f..3df7d26fb67 100644
--- a/src/Analyser/TypeSpecifier.php
+++ b/src/Analyser/TypeSpecifier.php
@@ -58,6 +58,7 @@
 use PHPStan\Type\TypeUtils;
 use PHPStan\Type\TypeWithClassName;
 use PHPStan\Type\UnionType;
+use PHPStan\Type\VerbosityLevel;
 use function array_merge;
 use function array_reverse;
 use function count;
@@ -242,6 +243,24 @@ public function specifyTypesInCondition(
 						}
 					}
 				}
+
+				if (
+					$exprNode instanceof FuncCall
+					&& $exprNode->name instanceof Name
+					&& strtolower($exprNode->name->toString()) === 'substr'
+					&& isset($exprNode->getArgs()[0])
+					&& $constantType instanceof ConstantStringType
+					&& $constantType->getValue() !== ''
+					&& $scope->getType($exprNode->getArgs()[0]->value)->isString()->yes()
+				) {
+					return $this->create(
+						$exprNode->getArgs()[0]->value,
+						TypeCombinator::intersect($scope->getType($exprNode->getArgs()[0]->value), new AccessoryNonEmptyStringType()),
+						$context,
+						false,
+						$scope
+					);
+				}
 			}
 
 			$rightType = $scope->getType($expr->right);
diff --git a/tests/PHPStan/Analyser/NodeScopeResolverTest.php b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
index 92b3dd7059b..558fd50f811 100644
--- a/tests/PHPStan/Analyser/NodeScopeResolverTest.php
+++ b/tests/PHPStan/Analyser/NodeScopeResolverTest.php
@@ -903,6 +903,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-7115.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/constant-array-type-identical.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/non-empty-string-str-containing-fns.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/non-empty-string-substr-specifying.php');
 	}
 
 	/**
diff --git a/tests/PHPStan/Analyser/data/non-empty-string-substr-specifying.php b/tests/PHPStan/Analyser/data/non-empty-string-substr-specifying.php
new file mode 100644
index 00000000000..6c10dab1306
--- /dev/null
+++ b/tests/PHPStan/Analyser/data/non-empty-string-substr-specifying.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace NonEmptyStringSubstr;
+
+use function PHPStan\Testing\assertType;
+
+class Foo {
+	public function nonEmptySubstr(string $s, int $offset, int $length): void
+	{
+		if (substr($s, 10) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, -10) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, 10, 5) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, 10, -5) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, $offset) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, $offset, $length) === 'hallo') {
+			assertType('non-empty-string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, $offset, $length) !== 'hallo') {
+			assertType('string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, $offset, $length) === '') {
+			assertType('string', $s);
+		}
+		assertType('string', $s);
+
+		if (substr($s, $offset, $length) == '') {
+			assertType('string', $s);
+		}
+		assertType('string', $s);
+
+	}
+}