Add compile warning for "confusable" types

We have a number of "types" like integer which are not actually
supported as builtin types -- instead they are silently interpreted
as class types.

I've seen this cause confusion a few types already. This change adds
a warning in this case. In the unlikely case that someone legitimately
wants to type against an integer class, the warning can be suppressed
by writing \integer or "use integer", or using Integer (this warning
will only trigger for lowercase spellings).

Closes GH-4815.

Zend/tests/type_declarations/confusable_type_warning.phpt

@@ -0,0 +1,46 @@
+--TEST--
+Warnings for confusable types
+--FILE--
+<?php
+
+function test1(integer $x) {}
+function test2(double $x) {}
+function test3(boolean $x) {}
+function test4(resource $x) {}
+
+namespace Foo {
+    use integer as foo;
+
+    function test5(\integer $x) {}
+    function test6(namespace\integer $x) {}
+    function test7(foo $x) {}
+    function test8(boolean $x) {}
+}
+
+namespace Foo {
+    use integer;
+    function test9(integer $x) {}
+}
+
+namespace {
+    use integer as foo;
+
+    function test10(\integer $x) {}
+    function test11(namespace\integer $x) {}
+    function test12(foo $x) {}
+    function test13(boolean $x) {}
+}
+
+?>
+--EXPECTF--
+Warning: "integer" will be interpreted as a class name. Did you mean "int"? Write "\integer" to suppress this warning in %s on line %d
+
+Warning: "double" will be interpreted as a class name. Did you mean "float"? Write "\double" to suppress this warning in %s on line %d
+
+Warning: "boolean" will be interpreted as a class name. Did you mean "bool"? Write "\boolean" to suppress this warning in %s on line %d
+
+Warning: "resource" is not a supported builtin type and will be interpreted as a class name. Write "\resource" to suppress this warning in %s on line %d
+
+Warning: "boolean" will be interpreted as a class name. Did you mean "bool"? Write "\Foo\boolean" or import the class with "use" to suppress this warning in %s on line %d
+
+Warning: "boolean" will be interpreted as a class name. Did you mean "bool"? Write "\boolean" to suppress this warning in %s on line %d

Zend/zend_compile.c

@@ -221,6 +221,19 @@ static const builtin_type_info builtin_types[] = {
 	{NULL, 0, IS_UNDEF}
 };
 
+typedef struct {
+	const char *name;
+	size_t name_len;
+	const char *correct_name;
+} confusable_type_info;
+
+static const confusable_type_info confusable_types[] = {
+	{ZEND_STRL("boolean"), "bool"},
+	{ZEND_STRL("integer"), "int"},
+	{ZEND_STRL("double"), "float"},
+	{ZEND_STRL("resource"), NULL},
+	{NULL, 0, NULL},
+};
 
 static zend_always_inline zend_uchar zend_lookup_builtin_type_by_name(const zend_string *name) /* {{{ */
 {
@@ -238,6 +251,43 @@ static zend_always_inline zend_uchar zend_lookup_builtin_type_by_name(const zend
 }
 /* }}} */
 
+static zend_always_inline zend_bool zend_is_confusable_type(const zend_string *name, const char **correct_name) /* {{{ */
+{
+	const confusable_type_info *info = confusable_types;
+
+	/* Intentionally using case-sensitive comparison here, because "integer" is likely intended
+	 * as a scalar type, while "Integer" is likely a class type. */
+	for (; info->name; ++info) {
+		if (ZSTR_LEN(name) == info->name_len
+			&& memcmp(ZSTR_VAL(name), info->name, info->name_len) == 0
+		) {
+			*correct_name = info->correct_name;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+/* }}} */
+
+static void *zend_hash_find_ptr_lc(HashTable *ht, const char *str, size_t len) {
+	void *result;
+	zend_string *lcname;
+	ALLOCA_FLAG(use_heap);
+
+	ZSTR_ALLOCA_ALLOC(lcname, len, use_heap);
+	zend_str_tolower_copy(ZSTR_VAL(lcname), str, len);
+	result = zend_hash_find_ptr(ht, lcname);
+	ZSTR_ALLOCA_FREE(lcname, use_heap);
+
+	return result;
+}
+
+static zend_bool zend_is_not_imported(zend_string *name) {
+	/* Assuming "name" is unqualified here. */
+	return !FC(imports)
+		|| zend_hash_find_ptr_lc(FC(imports), ZSTR_VAL(name), ZSTR_LEN(name)) == NULL;
+}
 
 void zend_oparray_context_begin(zend_oparray_context *prev_context) /* {{{ */
 {
@@ -809,19 +859,6 @@ zend_string *zend_prefix_with_ns(zend_string *name) {
 	}
 }
 
-void *zend_hash_find_ptr_lc(HashTable *ht, const char *str, size_t len) {
-	void *result;
-	zend_string *lcname;
-	ALLOCA_FLAG(use_heap);
-
-	ZSTR_ALLOCA_ALLOC(lcname, len, use_heap);
-	zend_str_tolower_copy(ZSTR_VAL(lcname), str, len);
-	result = zend_hash_find_ptr(ht, lcname);
-	ZSTR_ALLOCA_FREE(lcname, use_heap);
-
-	return result;
-}
-
 zend_string *zend_resolve_non_class_name(
 	zend_string *name, uint32_t type, zend_bool *is_fully_qualified,
 	zend_bool case_sensitive, HashTable *current_import_sub
@@ -5361,6 +5398,8 @@ static zend_type zend_compile_typename(zend_ast *ast, zend_bool force_allow_null
 			}
 			return ZEND_TYPE_ENCODE_CODE(type, allow_null);
 		} else {
+			const char *correct_name;
+			zend_string *orig_name = zend_ast_get_str(ast);
 			uint32_t fetch_type = zend_get_class_fetch_type_ast(ast);
 			if (fetch_type == ZEND_FETCH_CLASS_DEFAULT) {
 				class_name = zend_resolve_class_name_ast(ast);
@@ -5370,6 +5409,25 @@ static zend_type zend_compile_typename(zend_ast *ast, zend_bool force_allow_null
 				zend_string_addref(class_name);
 			}
 
+			if (ast->attr == ZEND_NAME_NOT_FQ
+					&& zend_is_confusable_type(orig_name, &correct_name)
+					&& zend_is_not_imported(orig_name)) {
+				const char *extra =
+					FC(current_namespace) ? " or import the class with \"use\"" : "";
+				if (correct_name) {
+					zend_error(E_COMPILE_WARNING,
+						"\"%s\" will be interpreted as a class name. Did you mean \"%s\"? "
+						"Write \"\\%s\"%s to suppress this warning",
+						ZSTR_VAL(orig_name), correct_name, ZSTR_VAL(class_name), extra);
+				} else {
+					zend_error(E_COMPILE_WARNING,
+						"\"%s\" is not a supported builtin type "
+						"and will be interpreted as a class name. "
+						"Write \"\\%s\"%s to suppress this warning",
+						ZSTR_VAL(orig_name), ZSTR_VAL(class_name), extra);
+				}
+			}
+
 			return ZEND_TYPE_ENCODE_CLASS(class_name, allow_null);
 		}
 	}