v3: validate fastc match and call visibility

Author: medvednikov

vlib/v3/gen/fastc/fastc.v

@@ -204,6 +204,8 @@ struct FastcFunctionSignature {
 	return_types    []string
 	option_type     string
 	is_variadic     bool
+	is_public       bool
+	module_name     string
 	path            string
 }
 
@@ -1670,6 +1672,7 @@ fn collect_function_signatures(source string, path string, header FastcSourceHea
 	mut tok := scan.scan()
 	for tok != .eof {
 		if tok == .key_fn && brace_depth == 0 && previous_tok != .assign {
+			is_public := previous_tok == .key_pub
 			tok = scan.scan()
 			mut parameter_types := []string{}
 			mut receiver_type := ''
@@ -1868,6 +1871,8 @@ fn collect_function_signatures(source string, path string, header FastcSourceHea
 				return_types:    return_types
 				option_type:     option_type
 				is_variadic:     is_variadic
+				is_public:       is_public || is_c_function
+				module_name:     header.module_name
 				path:            path
 			}
 			if previous := functions[function_key] {
@@ -2117,6 +2122,8 @@ fn collect_interface_method_signatures(source string, path string, header FastcS
 				return_type:     return_type
 				return_types:    return_types
 				option_type:     option_type
+				is_public:       true
+				module_name:     header.module_name
 				path:            path
 			}
 			interface_methods[interface_method_key] = true
@@ -3455,12 +3462,14 @@ fn (mut g Parser) parse_match_statement() !bool {
 	is_string := subject_type == 'string'
 	mut branch_index := 0
 	mut all_terminate := true
+	mut has_else := false
 	g.skip_semicolons()
 	for g.tok != .rcbr {
 		if g.tok == .eof {
 			return g.unsupported('unfinished match statement')
 		}
 		is_else := g.tok == .key_else
+		has_else = has_else || is_else
 		mut values := []string{}
 		if is_else {
 			g.next()
@@ -3523,7 +3532,7 @@ fn (mut g Parser) parse_match_statement() !bool {
 	}
 	g.next()
 	g.skip_semicolons()
-	return all_terminate
+	return has_else && all_terminate
 }
 
 fn (mut g Parser) parse_comptime_if_statement() !bool {
@@ -9017,6 +9026,11 @@ fn (g &Parser) validate_expression_calls(tokens []FastcExpressionToken) ! {
 			}
 		}
 		if signature := g.functions[function_key] {
+			if !signature.is_public && signature.module_name != ''
+				&& signature.module_name != g.module_name && signature.module_name != 'builtin'
+				&& signature.module_name in g.imports.values() {
+				return g.unsupported('private function `${name}` from imported module `${signature.module_name}`')
+			}
 			argument_offset := if is_method_call { 1 } else { 0 }
 			is_variadic := signature.is_variadic
 			expected_arguments := signature.parameter_types.len - argument_offset - if is_variadic {

vlib/v3/gen/fastc/fastc_test.v

@@ -102,6 +102,34 @@ fn test_generate_files_resolves_modules_without_an_ast() {
 	assert run_result.output.trim_space() == '42'
 }
 
+fn test_generate_files_rejects_private_imported_functions() {
+	root := os.join_path(os.vtmp_dir(), 'v3_fastc_private_import_${os.getpid()}')
+	os.rmdir_all(root) or {}
+	os.mkdir_all(os.join_path(root, 'secrets')) or { panic(err) }
+	defer {
+		os.rmdir_all(root) or {}
+	}
+	main_file := os.join_path(root, 'main.v')
+	module_file := os.join_path(root, 'secrets', 'secrets.v')
+	os.write_file(main_file,
+		'module main\nimport secrets\nfn main() { println(secrets.secret()) }\n') or { panic(err) }
+	os.write_file(module_file, 'module secrets\nfn secret() int { return 42 }\n') or { panic(err) }
+	mut prefs := pref.new_preferences()
+	prefs.module_search_paths = [root]
+	mut message := ''
+	_ := generate_files([main_file], prefs) or {
+		message = err.msg()
+		''
+	}
+	assert message.contains('private function `secret` from imported module `secrets`'), message
+
+	os.write_file(module_file, 'module secrets\npub fn secret() int { return 42 }\n') or {
+		panic(err)
+	}
+	c_source := generate_files([main_file], prefs) or { panic(err) }
+	assert c_source.contains('println(secrets__secret());'), c_source
+}
+
 fn test_disabled_function_attributes_emit_empty_stubs() {
 	mut prefs := pref.new_preferences()
 	prefs.user_defines = []
@@ -391,6 +419,44 @@ fn main() {
 	assert c_source.contains('? (7) : (9)')
 }
 
+fn test_match_statement_without_else_does_not_terminate_function() {
+	prefs := pref.new_preferences()
+	mut message := ''
+	_ := generate('module main
+
+fn value(x int) int {
+	match x {
+		1 { return 7 }
+	}
+}
+
+fn main() {
+	println(value(1))
+}
+',
+		'non_exhaustive_match_statement.v', prefs) or {
+		message = err.msg()
+		''
+	}
+	assert message.contains('non-void function `value` that can fall through'), message
+
+	c_source := generate('module main
+
+fn value(x int) int {
+	match x {
+		1 { return 7 }
+		else { return 9 }
+	}
+}
+
+fn main() {
+	println(value(1))
+}
+',
+		'exhaustive_match_statement.v', prefs) or { panic(err) }
+	assert c_source.contains('else {\n\t\treturn 9;'), c_source
+}
+
 fn test_c_reserved_identifiers_are_escaped_consistently() {
 	prefs := pref.new_preferences()
 	c_source := generate('module main