Added blocks and scopes section (#1822)

src/SUMMARY.md

@@ -37,6 +37,7 @@
   - [`break` and `continue`](control-flow-basics/break-continue.md)
     - [Labels](control-flow-basics/break-continue/labels.md)
   - [Blocks and Scopes](control-flow-basics/blocks-and-scopes.md)
+    - [Scopes and Shadowing](control-flow-basics/blocks-and-scopes/scopes.md)
   - [Functions](control-flow-basics/functions.md)
   - [Macros](control-flow-basics/macros.md)
   - [Exercise: Collatz Sequence](control-flow-basics/exercise.md)

src/control-flow-basics/blocks-and-scopes.md

@@ -24,40 +24,9 @@ fn main() {
 
 If the last expression ends with `;`, then the resulting value and type is `()`.
 
-## Scopes and Shadowing
-
-A variable's scope is limited to the enclosing block.
-
-You can shadow variables, both those from outer scopes and variables from the
-same scope:
-
-```rust,editable
-fn main() {
-    let a = 10;
-    println!("before: {a}");
-    {
-        let a = "hello";
-        println!("inner scope: {a}");
-
-        let a = true;
-        println!("shadowed in inner scope: {a}");
-    }
-
-    println!("after: {a}");
-}
-```
-
 <details>
 
 - You can show how the value of the block changes by changing the last line in
   the block. For instance, adding/removing a semicolon or using a `return`.
-- Show that a variable's scope is limited by adding a `b` in the inner block in
-  the last example, and then trying to access it outside that block.
-- Shadowing is different from mutation, because after shadowing both variable's
-  memory locations exist at the same time. Both are available under the same
-  name, depending where you use it in the code.
-- A shadowing variable can have a different type.
-- Shadowing looks obscure at first, but is convenient for holding on to values
-  after `.unwrap()`.
 
 </details>

src/control-flow-basics/blocks-and-scopes/scopes.md

@@ -0,0 +1,35 @@
+# Scopes and Shadowing
+
+A variable's scope is limited to the enclosing block.
+
+You can shadow variables, both those from outer scopes and variables from the
+same scope:
+
+```rust,editable
+fn main() {
+    let a = 10;
+    println!("before: {a}");
+    {
+        let a = "hello";
+        println!("inner scope: {a}");
+
+        let a = true;
+        println!("shadowed in inner scope: {a}");
+    }
+
+    println!("after: {a}");
+}
+```
+
+<details>
+
+- Show that a variable's scope is limited by adding a `b` in the inner block in
+  the last example, and then trying to access it outside that block.
+- Shadowing is different from mutation, because after shadowing both variable's
+  memory locations exist at the same time. Both are available under the same
+  name, depending where you use it in the code.
+- A shadowing variable can have a different type.
+- Shadowing looks obscure at first, but is convenient for holding on to values
+  after `.unwrap()`.
+
+</details>