Resolve loose comparison of two strings or two integers as identical

Two strings of which one is not numeric, and two integers, cannot coerce,
so their loose comparison is the identical one. resolveEqualType() now
answers it through resolveIdenticalType() like the narrowing in
IdenticalNarrowingHelper already does, instead of computing the values
each side can loosely equal for every PHP version in the configured
range. A switch over a string with many case labels or a long chain of
`$string == 'constant'` conditions spent most of its time there.

Amp-Thread-ID: https://ampcode.com/threads/T-01a1b250-12b7-7206-9d98-c1f38e89010e

Author: ondrejmirtes

src/Reflection/InitializerExprTypeResolver.php

@@ -1185,6 +1185,15 @@ public function resolveEqualType(Type $leftType, Type $rightType, ?PhpVersions $
 			return $this->resolveIdenticalType($leftType, $rightType);
 		}
 
+		// same-type sides cannot coerce - loose equals strict, except for
+		// two numeric strings, which compare as numbers
+		if (
+			($leftType->isString()->yes() && $rightType->isString()->yes() && ($leftType->isNumericString()->no() || $rightType->isNumericString()->no()))
+			|| ($leftType->isInteger()->yes() && $rightType->isInteger()->yes())
+		) {
+			return $this->resolveIdenticalType($leftType, $rightType);
+		}
+
 		if ($leftType instanceof ConstantArrayType && $rightType instanceof ConstantArrayType) {
 			return $this->resolveConstantArrayTypeComparison($leftType, $rightType, fn ($leftValueType, $rightValueType): TypeResult => $this->resolveEqualType($leftValueType, $rightValueType, $phpVersions));
 		}