feat(zend): enforce variance markers on function-origin type parameters

Signed-off-by: azjezz <azjezz@protonmail.com>

Author: azjezz

Zend/tests/generics/declaration/variance/arrow_violation_covariant_in_param.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Variance: +T on an arrow function in parameter position is rejected
+--FILE--
+<?php
+$f = fn<+T>(T $x): T => $x;
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d

Zend/tests/generics/declaration/variance/closure_violation_covariant_in_param.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Variance: +T on a closure in parameter position is rejected
+--FILE--
+<?php
+$f = function <+T>(T $x): void {};
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d

Zend/tests/generics/declaration/variance/function_happy_path.phpt

@@ -0,0 +1,29 @@
+--TEST--
+Variance: function-origin type parameters checked uniformly with class-origin
+--FILE--
+<?php
+function take<-T>(T $x): int { return 0; }
+function make<+T>(): T { return null; }
+function transform<-I, +O>(I $input): O { return null; }
+
+$closure_take = function <-T>(T $x): int { return 0; };
+$closure_make = function <+T>(): T { return null; };
+$arrow_take   = fn<-T>(T $x): int => 0;
+$arrow_make   = fn<+T>(): T => null;
+
+class A<+T> {
+    public function map<-A_, +B>(A_ $a): B { return null; }
+}
+
+take(42);
+make();
+transform(1);
+$closure_take(7);
+$closure_make();
+$arrow_take(7);
+$arrow_make();
+(new A)->map(42);
+echo "ok\n";
+?>
+--EXPECT--
+ok

Zend/tests/generics/declaration/variance/function_violation_composed.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Variance: function-origin +T composed through Consumer<-U> in return is rejected
+--FILE--
+<?php
+interface Consumer<-U> { public function consume(U $x): void; }
+
+function f<+T>(): Consumer<T> {}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d

Zend/tests/generics/declaration/variance/function_violation_contravariant_in_return.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Variance: -T on a function in return position (covariant) is rejected
+--FILE--
+<?php
+function f<-T>(): T {}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared contravariant (-T) cannot appear in covariant position in %s on line %d

Zend/tests/generics/declaration/variance/function_violation_covariant_in_param.phpt

@@ -0,0 +1,8 @@
+--TEST--
+Variance: +T on a function in parameter position (contravariant) is rejected
+--FILE--
+<?php
+function f<+T>(T $x): void {}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d

Zend/tests/generics/declaration/variance/function_violation_own_bound.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Variance: +T on a function appearing in its own bound (invariant position) is rejected
+--FILE--
+<?php
+interface Box<U> {}
+
+function f<+T : Box<T>>(): void {}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in invariant position in %s on line %d

Zend/tests/generics/declaration/variance/method_function_origin_violation.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Variance: +T on a method's own type parameter in parameter position is rejected
+--FILE--
+<?php
+class A {
+    public function f<+T>(T $x): void {}
+}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d

Zend/tests/generics/declaration/variance/mixed_class_T_and_function_T.phpt

@@ -0,0 +1,13 @@
+--TEST--
+Variance: class-T and function-T variance markers are checked independently in the same method
+--FILE--
+<?php
+class C<+T> {
+    public function map<-A, +B>(A $a): B { return null; }
+}
+
+(new C)->map(42);
+echo "ok\n";
+?>
+--EXPECT--
+ok

Zend/tests/generics/declaration/variance/static_method_function_origin_violation.phpt

@@ -0,0 +1,10 @@
+--TEST--
+Variance: +T on a static method's own type parameter in parameter position is rejected
+--FILE--
+<?php
+class A {
+    public static function f<+T>(T $x): void {}
+}
+?>
+--EXPECTF--
+Fatal error: Type parameter T declared covariant (+T) cannot appear in contravariant position in %s on line %d