handle inference for scalar values

Signed-off-by: Robert Landers <landers.robert@gmail.com>

Author: withinboredom

Zend/tests/generics/reification/composite_return_reification.phpt

@@ -29,6 +29,13 @@ function par<T>(T|Other $x): string { return $x::class; }
 var_dump(par::<Foo>(new Foo));
 try { par::<Foo>(42); } catch (TypeError $e) { echo $e->getMessage(), "\n"; }
 
+// Parameters fold/flatten through the same path as returns: T=Other folds the
+// duplicate, and a union binding flattens. The reified param type is observable.
+par::<Other>(new Other);
+var_dump((string) (new ReflectionFunction('par<Other>'))->getParameters()[0]->getType());
+par::<Foo|Other>(new Foo);
+var_dump((string) (new ReflectionFunction('par<Foo|Other>'))->getParameters()[0]->getType());
+
 // Intersection return: T bound to an interface, T&B reifies to A&B.
 function inter<T: A>(mixed $x): T&B { return $x; }
 var_dump(inter::<A>(new AB)::class);
@@ -51,6 +58,8 @@ string(5) "Other"
 two(): Return value must be of type Foo|Other, int returned
 string(3) "Foo"
 par(): Argument #1 ($x) must be of type Foo|Other, int given, called in %s on line %d
+string(5) "Other"
+string(9) "Foo|Other"
 string(2) "AB"
 inter(): Return value must be of type A&B, Foo returned
 string(2) "AB"

Zend/zend_compile.c

@@ -1165,6 +1165,30 @@ ZEND_API zend_type_arg_table *zend_build_generic_call_type_args(
 				zend_string *inferred_name = zend_string_copy(arg_ce->name);
 				table->entries[ref->index].owned_type =
 					(zend_type) ZEND_TYPE_INIT_CLASS(inferred_name, 0, 0);
+			} else {
+				/* Scalar/array values infer to their builtin type. Map the
+				 * zval type to a type code, synthesise a mask owned_type, and
+				 * take its canonical name ("int", "string", ...) so reflection
+				 * and a reified `: T` return enforce the inferred type instead
+				 * of collapsing to the default. IS_TRUE/IS_FALSE both map to
+				 * bool; IS_NULL and other non-reifiable kinds (resources) are
+				 * left for the declared default. */
+				uint32_t type_mask = 0;
+				switch (Z_TYPE_P(arg)) {
+					case IS_LONG:   type_mask = MAY_BE_LONG;   break;
+					case IS_DOUBLE: type_mask = MAY_BE_DOUBLE; break;
+					case IS_STRING: type_mask = MAY_BE_STRING; break;
+					case IS_ARRAY:  type_mask = MAY_BE_ARRAY;  break;
+					case IS_TRUE:
+					case IS_FALSE:  type_mask = MAY_BE_BOOL;   break;
+					default: break;
+				}
+				if (type_mask) {
+					zend_type inferred = (zend_type) ZEND_TYPE_INIT_MASK(type_mask);
+					table->entries[ref->index].name =
+						zend_type_arg_canonical_name(inferred);
+					table->entries[ref->index].owned_type = inferred;
+				}
 			}
 		} ZEND_HASH_FOREACH_END();
 	}