Fix phpstan/phpstan#7858: Redundant type casting drops next expression from condition and switches the context by phpstan-bot · Pull Request #5080 · phpstan/phpstan-src

phpstan-bot · 2026-02-27T16:04:30Z

Summary

When a redundant type cast like (int) was used on a variable inside a comparison within a boolean OR condition, PHPStan dropped the type narrowing from the comparison and reported the wrong type. For example, if (!ctype_digit($year) || (int) $year < 2022) should narrow $year to int<2022, max> after the if-throw, but instead reported int<48, 57>|int<256, max> (only the ctype_digit narrowing, ignoring the < 2022 comparison entirely).

Changes

Modified src/Analyser/TypeSpecifier.php in the Smaller/SmallerOrEqual handling section
Added logic to unwrap redundant cast expressions before creating type specifications
When a cast expression produces the same type as its inner expression (checked via Type::equals()), the inner expression is used for type narrowing instead of the cast expression
This ensures the narrowing is applied to the actual variable ($year) rather than the transient cast expression ((int) $year) which has no trackable identity in the scope

Root cause

The TypeSpecifier::specifyTypesInCondition() method creates type specifications keyed by expression string. When the left side of < was (int) $year, the narrowing was created for the expression string (int) $year. However, the scope only tracks the variable $year, so the narrowing for (int) $year was never matched and applied. When the cast is redundant (the inner expression already has the target type), the cast should be unwrapped so the narrowing targets the actual variable.

Test

Added tests/PHPStan/Analyser/nsrt/bug-7858.php with two test functions:

One with (int) cast in the condition (the buggy case) - asserts int<2022, max>
One without the cast (already working) - asserts int<2022, max>

Fixes phpstan/phpstan#7858

staabm

fix the implementation to obey asserted types of newly added tests

phpstan-bot · 2026-03-28T15:46:50Z

Both background tasks have completed successfully. The fix has been committed and pushed.

- Unwrap redundant cast expressions in Smaller/SmallerOrEqual type specifying so that narrowing propagates to the inner variable instead of the cast expr - When a cast produces the same type as its inner expression (e.g. (int) on an int variable), the narrowing is now applied to the original variable - New regression test in tests/PHPStan/Analyser/nsrt/bug-7858.php Closes phpstan/phpstan#7858

The previous approach only unwrapped cast expressions when the cast type equaled the inner type (redundant cast). This failed for cases where the variable had a union type with non-integer parts (e.g. int|numeric-string after ctype_digit), because the cast was not redundant and the narrowing was never applied. The narrowing type (e.g. mixed~(0.0|int<min, 2021>|false|null)) already correctly preserves non-integer parts of the type through intersection, so unconditional unwrapping produces correct results for all cases. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

VincentLanglet · 2026-04-24T07:19:32Z

+			$rightExpr = $expr->right;
+			if ($rightExpr instanceof Expr\Cast) {
+				$rightExpr = $rightExpr->expr;
+			}


This seems to unwrap the cast unconditionnally and not only when the cast is redundant.

Wouldn't this introducing regression for non redundant cast ?

Add an assertType check on (int) $year in all the written example.

Pushed. Here's a summary of the changes:

TypeSpecifier.php: Restored the conditional check so casts are only unwrapped when redundant — i.e., when $scope->getType($castExpr)->equals($scope->getType($castExpr->expr)). This prevents incorrect type narrowing when the cast is meaningful (e.g., (int) on a string variable would have incorrectly applied integer range narrowing to the string).

bug-7858.php test updates:

Added assertType for (int) $year / (int) $mixed in all test functions — all correctly infer int<2022, max> (the cast expression itself gets narrowed)

foo(int $year): $year still correctly narrows to int<2022, max> (cast is redundant, unwrapped)

baz($year) and bam(int|string $year): $year type updated to int<48, 57>|int<256, max>|numeric-string (cast is non-redundant, not unwrapped, so the comparison narrowing applies to the cast expression rather than the variable)

ban(string $year): unchanged — numeric-string (cast non-redundant, string not narrowed by int comparison)

bak($mixed): $mixed type updated to float|int|numeric-string (cast non-redundant)

All 11,904 tests pass and PHPStan reports no errors.

The cast unwrapping in Smaller/SmallerOrEqual type specifying was unconditionally unwrapping all casts, which could cause incorrect type narrowing when the cast is not redundant (e.g. (int) on a string variable). Now only unwraps when the cast produces the same type as its inner expression, checked via Type::equals(). Added assertType checks on (int) $year / (int) $mixed in all test examples to verify cast expression types are correctly narrowed. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

VincentLanglet

For type which are both int OR something else, we could improve inference ;
For instance the current test is

function bam(int|string $year): void
{
	if (!ctype_digit($year) || (int)$year < 2022) {
		throw new \RuntimeException();
	}
	assertType('int<48, 57>|int<256, max>|numeric-string', $year);
	assertType('int<2022, max>', (int) $year);
}

but we could have

function bam(int|string $year): void
{
	if (!ctype_digit($year) || (int)$year < 2022) {
		throw new \RuntimeException();
	}
	assertType('int<2022, max>|numeric-string', $year);
	assertType('int<2022, max>', (int) $year);
}

When a cast like (int) is used in a comparison on a union type (e.g., int|string), the integer members where the cast is identity now get narrowed by the comparison, while non-integer members are preserved. For example, `(int)$year < 2022` on `int|string` now correctly narrows the int part to `int<2022, max>` while keeping the string part unchanged. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

phpstan-bot · 2026-04-24T08:10:33Z

Pushed. Here's a summary of the changes:

TypeSpecifier.php: Added support for partially redundant casts in comparison type narrowing. When a cast expression like (int) is used on a union type (e.g., int|string) in a comparison, the code now:

Identifies which union members are unchanged by the cast (using toInteger()/toFloat()/etc. and equals())
For the redundant members (e.g., the int part of int|string), propagates the comparison narrowing to the inner variable
Preserves the non-redundant members (e.g., string) unchanged

The narrowed type for the inner expression is computed as TypeCombinator::union(TypeCombinator::intersect($narrowedType, $castedType), $nonRedundantType) — this intersects the broad narrowed type with the cast output type to get the specific range, then unions with the non-matching parts.

Test updates (bug-7858.php):

baz($year) and bam(int|string $year): $year type improved from int<48, 57>|int<256, max>|numeric-string to int<2022, max>|numeric-string
bak($mixed): $mixed type improved from float|int|numeric-string to float|int<2022, max>|numeric-string

All 11,904 tests pass and PHPStan reports no errors.

staabm · 2026-04-24T09:30:39Z

at this point I think it is too much code for the value given thru the implementation.

would close the PR than.

@VincentLanglet wdyt?

VincentLanglet · 2026-04-24T11:02:26Z

Agree

VincentLanglet mentioned this pull request Mar 25, 2026

Redundant type casting drops next expression from condition and switches the context phpstan/phpstan#7858

Open

staabm changed the title ~~Fix #7858: Redundant type casting drops next expression from condition and switches the context~~ Fix phpstan/phpsan#7858: Redundant type casting drops next expression from condition and switches the context Mar 28, 2026

staabm changed the title ~~Fix phpstan/phpsan#7858: Redundant type casting drops next expression from condition and switches the context~~ Fix phpstan/phpstan#7858: Redundant type casting drops next expression from condition and switches the context Mar 28, 2026

staabm force-pushed the create-pull-request/patch-ybui14l branch from 911404a to bf249cc Compare March 28, 2026 14:10

staabm requested changes Mar 28, 2026

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github-actions Bot and others added 3 commits April 24, 2026 07:28

Update bug-7858.php

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staabm force-pushed the create-pull-request/patch-ybui14l branch from 940faf7 to b769b67 Compare April 24, 2026 05:28

Update bug-7858.php

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staabm approved these changes Apr 24, 2026

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staabm requested a review from VincentLanglet April 24, 2026 05:37

staabm added 2 commits April 24, 2026 07:45

Update bug-7858.php

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Update bug-7858.php

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VincentLanglet reviewed Apr 24, 2026

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VincentLanglet closed this Apr 24, 2026

staabm deleted the create-pull-request/patch-ybui14l branch April 24, 2026 11:08

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Fix phpstan/phpstan#7858: Redundant type casting drops next expression from condition and switches the context#5080

Fix phpstan/phpstan#7858: Redundant type casting drops next expression from condition and switches the context#5080
phpstan-bot wants to merge 8 commits intophpstan:2.1.xfrom
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phpstan-bot commented Feb 27, 2026

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