Merge pull request #3977 from SpectralPixel/listing-preprocessor-chap…

…ter-06

Convert Listings in Chapter 06 to `<Listing>`

src/ch06-01-defining-an-enum.md

@@ -59,12 +59,13 @@ only know what *kind* it is. Given that you just learned about structs in
 Chapter 5, you might be tempted to tackle this problem with structs as shown in
 Listing 6-1.
 
+<Listing number="6-1" caption="Storing the data and `IpAddrKind` variant of an IP address using a `struct`">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-01/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-1: Storing the data and `IpAddrKind` variant of
-an IP address using a `struct`</span>
+</Listing>
 
 Here, we’ve defined a struct `IpAddr` that has two fields: a `kind` field that
 is of type `IpAddrKind` (the enum we defined previously) and an `address` field
@@ -140,12 +141,13 @@ more about bringing types into scope in Chapter 7.
 Let’s look at another example of an enum in Listing 6-2: this one has a wide
 variety of types embedded in its variants.
 
+<Listing number="6-2" caption="A `Message` enum whose variants each store different amounts and types of values">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-02/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-2: A `Message` enum whose variants each store
-different amounts and types of values</span>
+</Listing>
 
 This enum has four variants with different types:
 

src/ch06-02-match.md

@@ -22,12 +22,13 @@ function that takes an unknown US coin and, in a similar way as the counting
 machine, determines which coin it is and returns its value in cents, as shown
 in Listing 6-3.
 
+<Listing number="6-3" caption="An enum and a `match` expression that has the variants of the enum as its patterns">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-03/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-3: An enum and a `match` expression that has
-the variants of the enum as its patterns</span>
+</Listing>
 
 Let’s break down the `match` in the `value_in_cents` function. First we list
 the `match` keyword followed by an expression, which in this case is the value
@@ -75,12 +76,13 @@ designs, so only quarters have this extra value. We can add this information to
 our `enum` by changing the `Quarter` variant to include a `UsState` value
 stored inside it, which we’ve done in Listing 6-4.
 
+<Listing number="6-4" caption="A `Coin` enum in which the `Quarter` variant also holds a `UsState` value">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-04/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-4: A `Coin` enum in which the `Quarter` variant
-also holds a `UsState` value</span>
+</Listing>
 
 Let’s imagine that a friend is trying to collect all 50 state quarters. While
 we sort our loose change by coin type, we’ll also call out the name of the
@@ -119,12 +121,13 @@ operations.
 This function is very easy to write, thanks to `match`, and will look like
 Listing 6-5.
 
+<Listing number="6-5" caption="A function that uses a `match` expression on an `Option<i32>`">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-05/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-5: A function that uses a `match` expression on
-an `Option<i32>`</span>
+</Listing>
 
 Let’s examine the first execution of `plus_one` in more detail. When we call
 `plus_one(five)`, the variable `x` in the body of `plus_one` will have the

src/ch06-03-if-let.md

@@ -6,12 +6,13 @@ program in Listing 6-6 that matches on an `Option<u8>` value in the
 `config_max` variable but only wants to execute code if the value is the `Some`
 variant.
 
+<Listing number="6-6" caption="A `match` that only cares about executing code when the value is `Some`">
+
 ```rust
 {{#rustdoc_include ../listings/ch06-enums-and-pattern-matching/listing-06-06/src/main.rs:here}}
 ```
 
-<span class="caption">Listing 6-6: A `match` that only cares about executing
-code when the value is `Some`</span>
+</Listing>
 
 If the value is `Some`, we print out the value in the `Some` variant by binding
 the value to the variable `max` in the pattern. We don’t want to do anything