compiler: add support for import/export statements

This commit introduces syntax level support for ES6 style module import
and export statements. Imports are resolved at compile time and the
corresponding module code is compiled into the main program.

Also add testcases to cover import and export statement semantics.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 89 insertions, 0 deletions

diff --git a/tests/custom/04_modules/06_export_errors b/tests/custom/04_modules/06_export_errors
new file mode 100644
index 0000000..c02a547
--- /dev/null
+++ b/tests/custom/04_modules/06_export_errors
@@ -0,0 +1,89 @@
+Export statements are only allowed at the toplevel of a module.
+
+-- Testcase --
+export let x = 1;
+-- End --
+
+-- Args --
+-R
+-- End --
+
+-- Expect stderr --
+Syntax error: Exports may only appear at top level of a module
+
+ `export let x = 1;`
+  ^-- Near here
+
+
+-- End --
+
+
+Export statements are not allowed within functions or nested blocks.
+
+-- Testcase --
+import "./files/test.uc";
+-- End --
+
+-- File test.uc --
+{
+	export let x = 1;
+}
+-- End --
+
+-- Args --
+-R
+-- End --
+
+-- Expect stderr --
+Syntax error: Unable to compile module './files/test.uc':
+Syntax error: Exports may only appear at top level of a module
+In line 2, byte 2:
+
+ `    export let x = 1;`
+      ^-- Near here
+
+
+
+In line 1, byte 25:
+
+ `import "./files/test.uc";`
+  Near here --------------^
+
+
+-- End --
+
+
+Duplicate export names should result in an error.
+
+-- Testcase --
+import "./files/test-duplicate.uc";
+-- End --
+
+-- File test-duplicate.uc --
+let x = 1, y = 2;
+
+export { x };
+export { y as x };
+-- End --
+
+-- Args --
+-R
+-- End --
+
+-- Expect stderr --
+Syntax error: Unable to compile module './files/test-duplicate.uc':
+Syntax error: Duplicate export 'x' for module './files/test-duplicate.uc'
+In line 4, byte 15:
+
+ `export { y as x };`
+  Near here ----^
+
+
+
+In line 1, byte 35:
+
+ `import "./files/test-duplicate.uc";`
+  Near here ------------------------^
+
+
+-- End --