Label all code with a filename

src/ch07-01-mod-and-the-filesystem.md

@@ -15,8 +15,10 @@ $ cargo new communicator
 $ cd communicator
 ```
 
-You'll notice that Cargo generated `src/lib.rs` instead of `src/main.rs` for
-us, and inside it we'll find this:
+Notice that Cargo generated `src/lib.rs` instead of `src/main.rs` for us, and
+inside it we'll find this:
+
+Filename: src/lib.rs
 
 ```rust
 #[cfg(test)]
@@ -55,6 +57,8 @@ rather than `connect()`.
 You could have multiple modules, side-by-side. For example, if you wanted a
 `client` module:
 
+Filename: src/lib.rs
+
 ```rust
 mod network {
     fn connect() {
@@ -72,6 +76,8 @@ Now we have a `network::connect` function and a `client::connect` function.
 And you can put modules inside of modules. If you wanted to have `client` be
 within `network`:
 
+Filename: src/lib.rs
+
 ```rust
 mod network {
     fn connect() {

src/ch07-02-controlling-visibility-with-pub.md

@@ -208,6 +208,8 @@ Overall, these are the rules for item visibility:
 Let's look at a few more examples to get some practice. What if we had this
 code in a new project's `src/lib.rs`:
 
+Filename: src/lib.rs
+
 ```rust,ignore
 mod outermost {
     pub fn middle_function() {}

src/ch07-03-importing-names-with-use.md

@@ -3,6 +3,8 @@
 We've seen how we can call functions defined within a module by using the
 module name as part of the call, like this:
 
+Filename: src/main.rs
+
 ```rust
 pub mod a {
     pub mod series {
@@ -21,6 +23,8 @@ However, referring to the fully qualified name can get quite lengthy, as we see
 in that example. To solve this issue, Rust has a keyword, `use`. It works like
 this:
 
+Filename: src/main.rs
+
 ```rust
 pub mod a {
     pub mod series {
@@ -132,6 +136,8 @@ Since tests are for exercising the code within our library, let's try to call
 our `client::connect` function from this `it_works` function, even though
 we're not going to be checking any functionality right now:
 
+Filename: src/lib.rs
+
 ```rust
 #[cfg(test)]
 mod tests {
@@ -193,6 +199,8 @@ instead of to the root module.
 For these reasons, in the `tests` module especially, `use super::something` is
 usually the way to go. So now our test looks like this:
 
+Filename: src/lib.rs
+
 ```rust
 #[cfg(test)]
 mod tests {