Improve diagnostics: replace 'non-inline module' with 'file module' and update note/help messages

Author: reddevilmidzy

compiler/rustc_expand/messages.ftl

@@ -118,8 +118,9 @@ expand_module_file_not_found =
  .note = if there is a `mod {$name}` elsewhere in the crate already, import it with `use crate::...` instead
 
 expand_module_in_block =
- cannot declare a non-inline module inside a block unless it has a path attribute
- .note = maybe `use` the module `{$name}` instead of redeclaring it
+ cannot declare a file module inside a block unless it has a path attribute
+ .help = maybe `use` the module `{$name}` instead of redeclaring it
+ .note = file modules are usually placed outside of blocks, at the top level of the file
 
 expand_module_multiple_candidates =
  file for module `{$name}` found at both "{$default_path}" and "{$secondary_path}"

compiler/rustc_expand/src/errors.rs

@@ -265,6 +265,7 @@ pub(crate) struct ModuleCircular {
 
 #[derive(Diagnostic)]
 #[diag(expand_module_in_block)]
+#[note]
 pub(crate) struct ModuleInBlock {
  #[primary_span]
  pub span: Span,
@@ -273,7 +274,7 @@ pub(crate) struct ModuleInBlock {
 }
 
 #[derive(Subdiagnostic)]
-#[note(expand_note)]
+#[help(expand_help)]
 pub(crate) struct ModuleInBlockName {
  #[primary_span]
  pub span: Span,

tests/ui/directory_ownership/file-mod-restriction.rs

@@ -0,0 +1,5 @@
+// Test that file modules are not allowed inside blocks.
+
+fn main() {
+ mod foo; //~ ERROR cannot declare a file module inside a block unless it has a path attribute
+}

tests/ui/directory_ownership/file-mod-restriction.stderr

@@ -0,0 +1,10 @@
+error: cannot declare a file module inside a block unless it has a path attribute
+ --> $DIR/file-mod-restriction.rs:4:5
+ |
+LL | mod foo;
+ | ^^^^^^^^
+ |
+ = note: file modules are usually placed outside of blocks, at the top level of the file
+
+error: aborting due to 1 previous error
+

tests/ui/directory_ownership/macro-expanded-mod.rs

@@ -1,8 +1,8 @@
-// Test that macro-expanded non-inline modules behave correctly
+// Test that macro-expanded file modules behave correctly
 
 macro_rules! mod_decl {
  ($i:ident) => {
- mod $i; //~ ERROR cannot declare a non-inline module inside a block
+ mod $i; //~ ERROR cannot declare a file module inside a block unless it has a path attribute
  };
 }
 

tests/ui/directory_ownership/macro-expanded-mod.stderr

@@ -1,4 +1,4 @@
-error: cannot declare a non-inline module inside a block unless it has a path attribute
+error: cannot declare a file module inside a block unless it has a path attribute
  --> $DIR/macro-expanded-mod.rs:5:9
  |
 LL | mod $i;
@@ -7,6 +7,7 @@ LL | mod $i;
 LL | mod_decl!(foo);
  | -------------- in this macro invocation
  |
+ = note: file modules are usually placed outside of blocks, at the top level of the file
  = note: this error originates in the macro `mod_decl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error