propsals-ideas/Better-error-messages.md

 
-This file holds the error messages that have been improved or added.
+This file describes the in progress work to improve the error messages.
+
+Let's just create simple expressions that should generate errors and then try to improve the error messages for those.
 
-# Starting functions with _
 
-This was actually an error that should have been raised, but it did not.
+```c
 
-The message for invalid function names simply reads: `invalid function name `%s' found`.
+int main() {
+    a = [1,2,3];
+    print(a);
+    return 0;
+}
 
-I added a specific case for when a function name written by the programmer starts with an _
+```
 
+
+# Starting functions with _
+
+Bodo thought that this was disallowed. But actually we should just discourage it.
 A [MR](https://gitlab.sac-home.org/sac-group/sac2c/-/merge_requests/362) was made for this but maybe its not the best solution to the problem of compiler generated functions.
 
 ## On a function call: 
@@ -17,4 +26,33 @@ Sorry, but only primitive functions are allowed to start with an _ (underscore)
 
 ## On a function definition: 
 
-Sorry, but function definition names are not allowed to start with an _ (underscore) character, but your '%s' function starts with an underscore. Please remove it.
+Sorry, but function definition names are not allowed to start with an _ (underscore) character, but your '%s' function starts with an underscore. Please remove it.
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+
+# No main function or module 
+
+Currently, if you try to compile an empty file you get:
+
+```
+Error:
+  No declaration of module, class, or main function given
+Compilation failed while Loading SAC program, 1 error(s).
+```
+
+This error is generated in the parser in the main `parse` function.
+
+I improved this error by suggesting to add an example hello world program.
+
+```
+Error:
+  No declaration of module, class, or main function given
+
+Every program needs 1 main function. 
+Try a hello world program like this: 
+
+int main() {
+	show("Hello world!");
+	return 0;
+}
+
+Compilation failed while Loading SAC program, 1 error(s).
+```
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