From 0605a8c5005a89334b3358cd07b2d07f9da2fab7 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Sun, 30 May 2021 15:11:12 +0200
Subject: [PATCH] Introduce "private" keyword and private modules / private
 import.

---
 resources/testfragments/parsertest.c3        |   2 +-
 src/compiler/compiler.c                      |   4 +-
 src/compiler/compiler_internal.h             |   5 +-
 src/compiler/context.c                       |  45 +++++---
 src/compiler/enums.h                         |   1 +
 src/compiler/lexer.c                         |  41 -------
 src/compiler/parse_global.c                  |  28 ++---
 src/compiler/parse_stmt.c                    |   1 +
 src/compiler/sema_decls.c                    |   2 +-
 src/compiler/sema_passes.c                   |  12 +-
 src/compiler/symtab.c                        |   2 +-
 src/compiler/tokens.c                        |   4 +-
 src/compiler_tests/tests.c                   | 115 +------------------
 test/test_suite/generic/generic_idents.c3t   |  91 +++++++++++++++
 test/test_suite/visibility/private_import.c3 |  21 ++++
 test/test_suite/visibility/private_module.c3 |  17 +++
 16 files changed, 192 insertions(+), 199 deletions(-)
 create mode 100644 test/test_suite/generic/generic_idents.c3t
 create mode 100644 test/test_suite/visibility/private_import.c3
 create mode 100644 test/test_suite/visibility/private_module.c3

diff --git a/resources/testfragments/parsertest.c3 b/resources/testfragments/parsertest.c3
index 481f69952..31f671b22 100644
--- a/resources/testfragments/parsertest.c3
+++ b/resources/testfragments/parsertest.c3
@@ -1,4 +1,4 @@
-module foo ($foo, #bar, Integer);
+module foo <$foo, #bar, Integer>;
 import bar as eok local;
 import bar2 as eok2;
 import bar3 local;
diff --git a/src/compiler/compiler.c b/src/compiler/compiler.c
index fd7ea830c..e4c325b29 100644
--- a/src/compiler/compiler.c
+++ b/src/compiler/compiler.c
@@ -281,6 +281,7 @@ void compiler_compile(void)
 
 	if (!global_context.module_list)
 	{
+		if (global_context.errors_found) exit(EXIT_FAILURE);
 		error_exit("No modules to compile.");
 	}
 	VECEACH(global_context.generic_module_list, i)
@@ -496,7 +497,7 @@ Module *global_context_find_module(const char *name)
 	return stable_get(&global_context.modules, name);
 }
 
-Module *compiler_find_or_create_module(Path *module_name, TokenId *parameters)
+Module *compiler_find_or_create_module(Path *module_name, TokenId *parameters, bool is_private)
 {
 	Module *module = global_context_find_module(module_name->module);
 	if (module) return module;
@@ -507,6 +508,7 @@ Module *compiler_find_or_create_module(Path *module_name, TokenId *parameters)
 	module->name = module_name;
 	module->stage = ANALYSIS_NOT_BEGUN;
 	module->parameters = parameters;
+	module->is_private = is_private;
 	stable_init(&module->symbols, 0x10000);
 	stable_set(&global_context.modules, module_name->module, module);
 	if (parameters)
diff --git a/src/compiler/compiler_internal.h b/src/compiler/compiler_internal.h
index a08e35ecf..a7a6aece5 100644
--- a/src/compiler/compiler_internal.h
+++ b/src/compiler/compiler_internal.h
@@ -1159,6 +1159,7 @@ typedef struct Module_
 	bool is_c_library : 1;
 	bool is_exported : 1;
 	bool is_generic : 1;
+	bool is_private : 1;
 	AnalysisStage stage : 6;
 
 	Ast **files; // Asts
@@ -1555,7 +1556,7 @@ void header_gen(Module *module);
 
 void global_context_add_type(Type *type);
 Decl *compiler_find_symbol(const char *name);
-Module *compiler_find_or_create_module(Path *module_name, TokenId *parameters);
+Module *compiler_find_or_create_module(Path *module_name, TokenId *parameters, bool is_private);
 Module *global_context_find_module(const char *name);
 void compiler_register_public_symbol(Decl *decl);
 
@@ -1564,7 +1565,7 @@ void context_register_global_decl(Context *context, Decl *decl);
 void context_register_external_symbol(Context *context, Decl *decl);
 bool context_add_import(Context *context, Path *path, Token symbol, Token alias, bool private_import);
 bool context_set_module_from_filename(Context *context);
-bool context_set_module(Context *context, Path *path, TokenId *generic_parameters);
+bool context_set_module(Context *context, Path *path, TokenId *generic_parameters, bool is_private);
 void context_print_ast(Context *context, FILE *file);
 
 #pragma mark --- Decl functions
diff --git a/src/compiler/context.c b/src/compiler/context.c
index 0dc095e23..2a849eb52 100644
--- a/src/compiler/context.c
+++ b/src/compiler/context.c
@@ -15,24 +15,39 @@ Context *context_create(File *file)
 }
 
 
-static inline bool create_module_or_check_name(Context *context, Path *module_name, TokenId *parameters)
+static inline bool create_module_or_check_name(Context *context, Path *module_name, TokenId *parameters, bool is_private)
 {
     context->module_name = module_name;
-    if (context->module == NULL)
-    {
-    	context->module = compiler_find_or_create_module(module_name, parameters);
-	    vec_add(context->module->contexts, context);
-	    return true;
-    }
+	if (context->module == NULL)
+	{
+		context->module = compiler_find_or_create_module(module_name, parameters, is_private);
+	}
+	else
+	{
+		if (context->module->name->module != module_name->module)
+		{
+			SEMA_ERROR(module_name,
+			           "Module name here '%s' did not match actual module '%s'.",
+			           module_name->module,
+			           context->module->name->module);
+			return false;
+		}
+	}
 
-    if (context->module->name->module != module_name->module)
+    if (context->module->is_private != is_private)
     {
-    	SEMA_ERROR(module_name, "Module name here '%s' did not match actual module '%s'.", module_name->module, context->module->name->module);
-        return false;
-    }
+    	if (is_private)
+	    {
+		    SEMA_ERROR(module_name, "The module is declared as private here, but was declared as public elsewhere.");
+	    }
+    	else
+	    {
+		    SEMA_ERROR(module_name, "The module is declared as public here, but was declared as private elsewhere.");
+	    }
+	    return false;
 
+    }
 	vec_add(context->module->contexts, context);
-
 	return true;
 }
 
@@ -58,10 +73,10 @@ bool context_set_module_from_filename(Context *context)
     path->span = INVALID_RANGE;
     path->module = module_name;
     path->len = len;
-    return create_module_or_check_name(context, path, NULL);
+    return create_module_or_check_name(context, path, NULL, true);
 }
 
-bool context_set_module(Context *context, Path *path, TokenId *generic_parameters)
+bool context_set_module(Context *context, Path *path, TokenId *generic_parameters, bool is_private)
 {
     // Note that we allow the illegal name for now, to be able to parse further.
     context->module_name = path;
@@ -71,7 +86,7 @@ bool context_set_module(Context *context, Path *path, TokenId *generic_parameter
         return false;
     }
 
-    return create_module_or_check_name(context, path, generic_parameters);
+    return create_module_or_check_name(context, path, generic_parameters, is_private);
 }
 
 
diff --git a/src/compiler/enums.h b/src/compiler/enums.h
index 7e69a9f53..5249b29e4 100644
--- a/src/compiler/enums.h
+++ b/src/compiler/enums.h
@@ -426,6 +426,7 @@ typedef enum
 	TOKEN_MODULE,
 	TOKEN_NEXTCASE,
 	TOKEN_NULL,
+	TOKEN_PRIVATE,
 	TOKEN_RETURN,
 	TOKEN_STATIC,
 	TOKEN_STRUCT,
diff --git a/src/compiler/lexer.c b/src/compiler/lexer.c
index b694989d9..f3f5921e1 100644
--- a/src/compiler/lexer.c
+++ b/src/compiler/lexer.c
@@ -1138,44 +1138,3 @@ void lexer_init_with_file(Lexer *lexer, File *file)
 
 }
 
-#pragma mark --- Test methods
-
-void lexer_init_for_test(Lexer *lexer, const char *text, size_t len)
-{
-	static File helper;
-	lexer->current_line = 1;
-	lexer->line_start = lexer->current;
-	lexer->lexing_start = text;
-	lexer->current = text;
-	lexer->file_begin = text;
-	lexer->current_file = &helper;
-	lexer->current_file->start_id = 0;
-	lexer->current_file->contents = text;
-	lexer->current_file->end_id = len;
-	lexer->current_file->name = "Test";
-}
-
-bool lexer_scan_ident_test(Lexer *lexer, const char *scan)
-{
-	static File helper;
-	lexer->lexing_start = scan;
-	lexer->current = scan;
-	lexer->file_begin = scan;
-	lexer->current_file = &helper;
-	lexer->current_file->start_id = 0;
-	lexer->current_file->contents = scan;
-	lexer->current_file->end_id = 1000;
-	lexer->current_file->name = "Foo";
-
-	if (scan[0] == '$')
-	{
-		next(lexer);
-		return scan_ident(lexer, TOKEN_CT_IDENT, TOKEN_CT_CONST_IDENT, TOKEN_CT_TYPE_IDENT, '$');
-	}
-	if (scan[0] == '#')
-	{
-		next(lexer);
-		return scan_ident(lexer, TOKEN_HASH_IDENT, TOKEN_HASH_CONST_IDENT, TOKEN_HASH_TYPE_IDENT, '#');
-	}
-	return scan_ident(lexer, TOKEN_IDENT, TOKEN_CONST_IDENT, TOKEN_TYPE_IDENT, 0);
-}
diff --git a/src/compiler/parse_global.c b/src/compiler/parse_global.c
index 179a26a8a..d7012e0de 100644
--- a/src/compiler/parse_global.c
+++ b/src/compiler/parse_global.c
@@ -342,6 +342,8 @@ bool parse_module(Context *context)
 		return context_set_module_from_filename(context);
 	}
 
+	bool is_private = try_consume(context, TOKEN_PRIVATE);
+
 	if (!TOKEN_IS(TOKEN_IDENT))
 	{
 		SEMA_TOKEN_ERROR(context->tok, "Module statement should be followed by the name of the module.");
@@ -357,7 +359,7 @@ bool parse_module(Context *context)
 		path->len = strlen("INVALID");
 		path->module = "INVALID";
 		path->span = INVALID_RANGE;
-		context_set_module(context, path, NULL);
+		context_set_module(context, path, NULL, false);
 		recover_top_level(context);
 		return false;
 	}
@@ -366,11 +368,11 @@ bool parse_module(Context *context)
 	TokenId *generic_parameters = NULL;
 	if (!parse_optional_module_params(context, &generic_parameters))
 	{
-		context_set_module(context, path, NULL);
+		context_set_module(context, path, NULL, is_private);
 		recover_top_level(context);
 		return true;
 	}
-	context_set_module(context, path, generic_parameters);
+	context_set_module(context, path, generic_parameters, is_private);
 	TRY_CONSUME_EOS_OR(false);
 	return true;
 }
@@ -2065,6 +2067,8 @@ static inline bool parse_import(Context *context)
 {
 	advance_and_verify(context, TOKEN_IMPORT);
 
+	bool private = try_consume(context, TOKEN_PRIVATE);
+
 	if (!TOKEN_IS(TOKEN_IDENT))
 	{
 		SEMA_TOKEN_ERROR(context->tok, "Import statement should be followed by the name of the module to import.");
@@ -2072,23 +2076,7 @@ static inline bool parse_import(Context *context)
 	}
 
 	Path *path = parse_module_path(context);
-	if (TOKEN_IS(TOKEN_COLON))
-	{
-		while (1)
-		{
-			if (!parse_specified_import(context, path)) return false;
-			if (!try_consume(context, TOKEN_COMMA)) break;
-		}
-	}
-	else
-	{
-		bool private = try_consume(context, TOKEN_AS);
-		if (private)
-		{
-			CONSUME_OR(TOKEN_MODULE, false);
-		}
-		context_add_import(context, path, NO_TOKEN, NO_TOKEN, private);
-	}
+	context_add_import(context, path, NO_TOKEN, NO_TOKEN, private);
 	TRY_CONSUME_EOS_OR(false);
 	return true;
 }
diff --git a/src/compiler/parse_stmt.c b/src/compiler/parse_stmt.c
index e49411d05..a085278ee 100644
--- a/src/compiler/parse_stmt.c
+++ b/src/compiler/parse_stmt.c
@@ -1166,6 +1166,7 @@ Ast *parse_stmt(Context *context)
 		case TOKEN_RBRAPIPE:
 		case TOKEN_BANGBANG:
 		case TOKEN_UNDERSCORE:
+		case TOKEN_PRIVATE:
 			SEMA_TOKEN_ERROR(context->tok, "Unexpected '%s' found when expecting a statement.", token_type_to_string(context->tok.type));
 			advance(context);
 			return poisoned_ast;
diff --git a/src/compiler/sema_decls.c b/src/compiler/sema_decls.c
index 30f6446f4..64ff08bcb 100644
--- a/src/compiler/sema_decls.c
+++ b/src/compiler/sema_decls.c
@@ -1018,7 +1018,7 @@ static Context *copy_context(Module *module, Context *c)
 
 static Module *sema_instantiate_module(Context *context, Module *module, Path *path, TypeInfo **parms)
 {
-	Module *new_module = compiler_find_or_create_module(path, NULL);
+	Module *new_module = compiler_find_or_create_module(path, NULL, module->is_private);
 	new_module->is_generic = true;
 	Context **contexts = module->contexts;
 	VECEACH(contexts, i)
diff --git a/src/compiler/sema_passes.c b/src/compiler/sema_passes.c
index 58a7518e2..096234ee2 100644
--- a/src/compiler/sema_passes.c
+++ b/src/compiler/sema_passes.c
@@ -57,12 +57,20 @@ void sema_analysis_pass_process_imports(Module *module)
 				continue;
 			}
 
-			// 7. Assign the module.
+			// 7. Importing private is not allowed.
+			if (import_module->is_private && !import->import.private)
+			{
+				SEMA_ERROR(import, "Importing a private module is not allowed (unless 'import private' is used).");
+				decl_poison(import);
+				continue;
+			}
+
+			// 8. Assign the module.
 			DEBUG_LOG("* Import of %s.", path->module);
 			import->module = import_module;
 			for (unsigned j = 0; j < i; j++)
 			{
-				// 7. We might run into multiple imports of the same package.
+				// 9. We might run into multiple imports of the same package.
 				if (import->module == context->imports[j]->module)
 				{
 					SEMA_ERROR(import, "Module '%s' was imported more than once, please remove the duplicates.", path->module);
diff --git a/src/compiler/symtab.c b/src/compiler/symtab.c
index 0d5412713..a0f250289 100644
--- a/src/compiler/symtab.c
+++ b/src/compiler/symtab.c
@@ -78,7 +78,7 @@ void symtab_init(uint32_t capacity)
 	symtab.capacity = capacity;
 
 	// Add keywords.
-	for (int i = 0; i < TOKEN_EOF; i++)
+	for (int i = 0; i < TOKEN_LAST; i++)
 	{
 		const char* name = token_type_to_string(i);
 		// Skip non-keywords
diff --git a/src/compiler/tokens.c b/src/compiler/tokens.c
index af46837b3..84fd73dac 100644
--- a/src/compiler/tokens.c
+++ b/src/compiler/tokens.c
@@ -232,6 +232,8 @@ const char *token_type_to_string(TokenType type)
 			return "nextcase";
 		case TOKEN_NULL:
 			return "null";
+		case TOKEN_PRIVATE:
+			return "private";
 		case TOKEN_RETURN:
 			return "return";
 		case TOKEN_STATIC:
@@ -307,7 +309,7 @@ const char *token_type_to_string(TokenType type)
 		case TOKEN_DOCS_END:
 			return "*/";
 		case TOKEN_DOCS_DIRECTIVE:
-			return "directive";
+			return "DIRECTIVE";
 		case TOKEN_DOCS_LINE:
 			return "DOCS_LINE";
 
diff --git a/src/compiler_tests/tests.c b/src/compiler_tests/tests.c
index c0aa1c67d..f606e4272 100644
--- a/src/compiler_tests/tests.c
+++ b/src/compiler_tests/tests.c
@@ -9,119 +9,7 @@
 #include "compiler/compiler_internal.h"
 #include "benchmark.h"
 
-static void test_lexer(void)
-{
-#ifdef __OPTIMIZE__
-	printf("--- RUNNING OPTIMIZED ---\n");
-#endif
-	run_arena_allocator_tests();
-	printf("Begin lexer testing.\n");
-	printf("-- Check number of keywords...\n");
-	int tokens_found = 0;
-	const int EXPECTED_TOKENS = TOKEN_CT_SWITCH - TOKEN_ALIAS + 1 + TOKEN_TYPEID - TOKEN_VOID + 1;
-	const char* tokens[TOKEN_EOF];
-	int len[TOKEN_EOF];
-	Lexer lexer;
-	for (int i = 1; i < TOKEN_EOF; i++)
-	{
-		const char* token = token_type_to_string((TokenType)i);
-		tokens[i] = token;
-		len[i] = (int)strlen(token);
-		TokenType lookup = TOKEN_IDENT;
-		const char* interned = symtab_add(token, len[i], fnv1a(token, len[i]), &lookup);
-		if (lookup != TOKEN_IDENT)
-		{
-			if (!lexer_scan_ident_test(&lexer, token))
-			{
-				TEST_ASSERT(false, "Failed to scan token %s", token);
-			}
-			int index = toktype_arena.allocated;
-			TokenType type_scanned = (TokenType)(toktypeptr(index - 1))[0];
-			TEST_ASSERT(type_scanned == (TokenType)i, "Mismatch scanning: was '%s', expected '%s' - lookup: %s - interned: %s.",
-					token_type_to_string(type_scanned),
-					token_type_to_string(i),
-					token_type_to_string(lookup),
-					interned);
-			tokens_found++;
-		}
-		else
-		{
-			tokens[i] = "casi";
-			len[i] = 4;
-		}
-	}
-	printf("-> %d keywords found.\n", tokens_found);
-	EXPECT("Keywords", tokens_found, EXPECTED_TOKENS);
 
-	const int BENCH_REPEATS = 10000;
-
-	printf("-- Test keyword lexing speed...\n");
-	bench_begin();
-	for (int b = 0; b < BENCH_REPEATS; b++)
-	{
-		for (int i = 1; i < TOKEN_EOF; i++)
-		{
-			volatile bool t = lexer_scan_ident_test(&lexer, tokens[i]);
-			(void)t;
-		}
-	}
-
-	printf("-> Test complete in %fs, %.0f kkeywords/s\n", bench_mark(), (BENCH_REPEATS * (TOKEN_EOF - 1)) / (1000 * bench_mark()));
-
-#include "shorttest.c"
-
-	printf("-- Test token lexing speed...\n");
-	const char *pointer = test_parse;
-	int loc = 0;
-	while (*pointer != '\0')
-	{
-		if (*(pointer++) == '\n') loc++;
-	}
-
-	bench_begin();
-	int tokens_parsed = 0;
-	size_t test_len = strlen(test_parse);
-	for (int b = 0; b < BENCH_REPEATS; b++)
-	{
-		lexer_init_for_test(&lexer, test_parse, test_len);
-		Token token;
-		while (1)
-		{
-			token = lexer_advance(&lexer);
-			if (token.type == TOKEN_EOF) break;
-			TEST_ASSERT(token.type != TOKEN_INVALID_TOKEN, "Got invalid token");
-
-			tokens_parsed++;
-		}
-	}
-
-	printf("-> Test complete in %fs, %.0f kloc/s, %.0f ktokens/s\n", bench_mark(),
-			loc * BENCH_REPEATS / (1000 * bench_mark()), tokens_parsed / (1000 * bench_mark()));
-}
-
-void test_compiler(void)
-{
-	const char **files = NULL;
-	file_add_wildcard_files(&files, "tests", true);
-	if (!vec_size(files))
-	{
-		error_exit("No test files could be found.");
-	}
-
-	const char **single_file = VECNEW(const char *, 1);
-	vec_add(single_file, files[0]);
-
-	VECEACH(files, i)
-	{
-		printf("Running %s...\n", files[i]);
-		char *res = NULL;
-		asprintf(&res, "tests/%s", files[i]);
-		single_file[0] = res;
-		active_target = (BuildTarget) { .type = TARGET_TYPE_EXECUTABLE, .sources = single_file, .name = "a.out" };
-		free(res);
-	}
-
-}
 
 void test_file(void)
 {
@@ -155,8 +43,7 @@ void compiler_tests(void)
 	symtab_init(0x100000);
 
 	test_file();
-	test_lexer();
-	test_compiler();
+	run_arena_allocator_tests();
 
 	exit(0);
 }
\ No newline at end of file
diff --git a/test/test_suite/generic/generic_idents.c3t b/test/test_suite/generic/generic_idents.c3t
new file mode 100644
index 000000000..14cb03b22
--- /dev/null
+++ b/test/test_suite/generic/generic_idents.c3t
@@ -0,0 +1,91 @@
+module gen <Type>;
+
+func Type mult(Type x)
+{
+    return x * x;
+}
+
+func Type addMult(Type x, Type a, Type b)
+{
+    return x * a + b;
+}
+
+module test;
+import gen;
+
+define intMult = gen::mult<int>;
+define doubleAddMult = gen::addMult<double>;
+
+func int getIt(int i)
+{
+    return intMult(i) + 1;
+}
+
+func double getIt2(double i)
+{
+    return doubleAddMult(i, 2, 3);
+}
+
+// #expect: gen.int.ll
+
+define i32 @gen.int.mult(i32 %0)
+  %x = alloca i32, align 4
+  store i32 %0, i32* %x, align 4
+  %1 = load i32, i32* %x, align 4
+  %2 = load i32, i32* %x, align 4
+  %mul = mul i32 %1, %2
+  ret i32 %mul
+
+; Function Attrs: nounwind
+define i32 @gen.int.addMult(i32 %0, i32 %1, i32 %2)
+  %x = alloca i32, align 4
+  %a = alloca i32, align 4
+  %b = alloca i32, align 4
+  store i32 %0, i32* %x, align 4
+  store i32 %1, i32* %a, align 4
+  store i32 %2, i32* %b, align 4
+  %3 = load i32, i32* %x, align 4
+  %4 = load i32, i32* %a, align 4
+  %mul = mul i32 %3, %4
+  %5 = load i32, i32* %b, align 4
+  %add = add i32 %mul, %5
+  ret i32 %add
+
+// #expect: test.ll
+
+declare i32 @gen.int.mult(i32)
+declare double @gen.double.addMult(double, double, double)
+
+define i32 @test.getIt(i32 %0)
+
+  %i = alloca i32, align 4
+  store i32 %0, i32* %i, align 4
+  %1 = load i32, i32* %i, align 4
+  %2 = call i32 @gen.int.mult(i32 %1)
+  %add = add i32 %2, 1
+  ret i32 %add
+
+define double @test.getIt2(double %0)
+
+  %i = alloca double, align 8
+  store double %0, double* %i, align 8
+  %1 = load double, double* %i, align 8
+  %2 = call double @gen.double.addMult(double %1, double 2.000000e+00, double 3.000000e+00)
+  ret double %2
+}
+
+// #expect: gen.double.ll
+
+define double @gen.double.addMult(double %0, double %1, double %2)
+  %x = alloca double, align 8
+  %a = alloca double, align 8
+  %b = alloca double, align 8
+  store double %0, double* %x, align 8
+  store double %1, double* %a, align 8
+  store double %2, double* %b, align 8
+  %3 = load double, double* %x, align 8
+  %4 = load double, double* %a, align 8
+  %fmul = fmul double %3, %4
+  %5 = load double, double* %b, align 8
+  %fadd = fadd double %fmul, %5
+  ret double %fadd
diff --git a/test/test_suite/visibility/private_import.c3 b/test/test_suite/visibility/private_import.c3
new file mode 100644
index 000000000..e5d22719a
--- /dev/null
+++ b/test/test_suite/visibility/private_import.c3
@@ -0,0 +1,21 @@
+module foo;
+
+static func void hidden()
+{
+}
+
+module bar;
+import foo;
+
+func void test()
+{
+    foo::hidden(); // #error: The function 'hidden' is not visible from this module.
+}
+
+module baz;
+import private foo;
+
+func void test()
+{
+    foo::hidden();
+}
\ No newline at end of file
diff --git a/test/test_suite/visibility/private_module.c3 b/test/test_suite/visibility/private_module.c3
new file mode 100644
index 000000000..631dafdf9
--- /dev/null
+++ b/test/test_suite/visibility/private_module.c3
@@ -0,0 +1,17 @@
+module private foo;
+
+func void hidden()
+{
+}
+
+module bar;
+import foo; // #error: Importing a private module is not allowed (unless 'import private' is used).
+
+
+module baz;
+import private foo;
+
+func void test()
+{
+    foo::hidden();
+}
\ No newline at end of file