Compute constant substr() result independently of the runtime PHP version

The is_bool($substr) branch re-checked substrReturnFalseInsteadOfEmptyString(),
which the sharper conditional guards proved always-true when analysing on PHP >= 8
(there substr() never returns false, so $substr is only bool via substrOrFalse()).
The finding is genuinely version-specific and cannot live in the shared baseline.
Route the non-mb_substr path through substrOrFalse(), whose false|string result
does not depend on the runtime substr() semantics, and map false to the analysed
version's result. Behaviour is unchanged; drops the version-specific baseline entry.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGhnJQpUWRRpg6H5LuWJkA

Author: ondrejmirtes

phpstan-baseline.neon

@@ -1566,12 +1566,6 @@ parameters:
 			count: 1
 			path: src/Type/Php/ReflectionMethodConstructorThrowTypeExtension.php
 
-		-
-			rawMessage: If condition is always true.
-			identifier: if.alwaysTrue
-			count: 1
-			path: src/Type/Php/SubstrDynamicReturnTypeExtension.php
-
 		-
 			rawMessage: 'Doing instanceof PHPStan\Type\ObjectType is error-prone and deprecated. Use Type::isObject() or Type::getObjectClassNames() instead.'
 			identifier: phpstanApi.instanceofType

src/Type/Php/SubstrDynamicReturnTypeExtension.php

@@ -23,7 +23,6 @@
 use PHPStan\Type\UnionType;
 use function count;
 use function in_array;
-use function is_bool;
 use function mb_substr;
 use function strlen;
 use function substr;
@@ -75,32 +74,25 @@ public function getTypeFromFunctionCall(
 		) {
 			$results = [];
 			foreach ($constantStrings as $constantString) {
-				if ($length !== null) {
-					if ($functionReflection->getName() === 'mb_substr') {
-						$substr = mb_substr($constantString->getValue(), $offset->getValue(), $length->getValue());
-					} elseif ($this->phpVersion->substrReturnFalseInsteadOfEmptyString()) {
-						$substr = $this->substrOrFalse($constantString->getValue(), $offset->getValue(), $length->getValue());
-					} else {
-						$substr = substr($constantString->getValue(), $offset->getValue(), $length->getValue());
-					}
-				} else {
-					if ($functionReflection->getName() === 'mb_substr') {
-						$substr = mb_substr($constantString->getValue(), $offset->getValue());
-					} elseif ($this->phpVersion->substrReturnFalseInsteadOfEmptyString()) {
-						// Simulate substr call on an older PHP version if the runtime one is too new.
-						$substr = $this->substrOrFalse($constantString->getValue(), $offset->getValue());
-					} else {
-						$substr = substr($constantString->getValue(), $offset->getValue());
-					}
+				if ($functionReflection->getName() === 'mb_substr') {
+					$substr = $length !== null
+						? mb_substr($constantString->getValue(), $offset->getValue(), $length->getValue())
+						: mb_substr($constantString->getValue(), $offset->getValue());
+					$results[] = new ConstantStringType($substr);
+					continue;
 				}
 
-				if (is_bool($substr)) {
-					if ($this->phpVersion->substrReturnFalseInsteadOfEmptyString()) {
-						$results[] = new ConstantBooleanType($substr);
-					} else {
-						// Simulate substr call on a recent PHP version if the runtime one is too old.
-						$results[] = new ConstantStringType('');
-					}
+				// substrOrFalse() detects an out-of-range offset with its own length
+				// check, so the result does not depend on the runtime PHP version's
+				// substr() semantics. false is then mapped to the analysed version's
+				// result: false on PHP < 8, an empty string on PHP >= 8.
+				$substr = $length !== null
+					? $this->substrOrFalse($constantString->getValue(), $offset->getValue(), $length->getValue())
+					: $this->substrOrFalse($constantString->getValue(), $offset->getValue());
+				if ($substr === false) {
+					$results[] = $this->phpVersion->substrReturnFalseInsteadOfEmptyString()
+						? new ConstantBooleanType(false)
+						: new ConstantStringType('');
 				} else {
 					$results[] = new ConstantStringType($substr);
 				}