Idiomatic: Misc. minor tweaks to the type system section

src/SUMMARY.md

@@ -487,7 +487,7 @@ SPDX-License-Identifier: CC-BY-4.0
 - [Leveraging the Type System](idiomatic/leveraging-the-type-system.md)
   - [Newtype Pattern](idiomatic/leveraging-the-type-system/newtype-pattern.md)
     - [Semantic Confusion](idiomatic/leveraging-the-type-system/newtype-pattern/semantic-confusion.md)
-    - [Parse, Don't Validate](idiomatic/leveraging-the-type-system/newtype-pattern/parse-don-t-validate.md)
+    - [Enforce Invariants](idiomatic/leveraging-the-type-system/newtype-pattern/parse-don-t-validate.md)
     - [Is It Encapsulated?](idiomatic/leveraging-the-type-system/newtype-pattern/is-it-encapsulated.md)
   - [RAII](idiomatic/leveraging-the-type-system/raii.md)
     - [Drop Skipped](idiomatic/leveraging-the-type-system/raii/drop_skipped.md)

src/idiomatic/leveraging-the-type-system/extension-traits.md

@@ -9,7 +9,7 @@ SPDX-License-Identifier: CC-BY-4.0
 
 # Extension Traits
 
-It may desirable to **extend** foreign types with new inherent methods. For
+It may desirable to **extend** foreign types with new methods. For
 example, allow your code to check if a string is a palindrome using
 method-calling syntax: `s.is_palindrome()`.
 

src/idiomatic/leveraging-the-type-system/newtype-pattern/parse-don-t-validate.md

@@ -7,7 +7,7 @@ Copyright 2025 Google LLC
 SPDX-License-Identifier: CC-BY-4.0
 -->
 
-# Parse, Don't Validate
+# Enforce Invariants at Construction
 
 The newtype pattern can be leveraged to enforce _invariants_.
 
@@ -25,7 +25,6 @@ impl Username {
         if username.len() > 32 {
             return Err(InvalidUsername::TooLong { len: username.len() })
         }
-        // Other validation checks...
         Ok(Self(username))
     }
 

src/idiomatic/leveraging-the-type-system/raii/scope_guard.md

@@ -60,8 +60,8 @@ fn main() {
   fails, the file will still be cleaned up. This ordering is essential for
   correctness.
 
-- The `guard()` creates a `ScopeGuard` instance. It a user-defined value (in
-  this case, `path`) and the cleanup closure that later receives this value.
+- The `guard()` creates a `ScopeGuard` instance. It takes a user-defined value
+  (in this case, `path`) and the cleanup closure that later receives this value.
 
 - The guard's closure runs on scope exit unless it is _defused_ with
   `ScopeGuard::into_inner` (removing the value so the guard does nothing on
@@ -75,8 +75,7 @@ fn main() {
 
 - This pattern is also useful when you don't control the cleanup strategy of the
   resource object. In this example, `File::drop()` closes the file but does not
-  delete it, and we can't change the standard library to delete the file instead
-  (nor should we, it is not a good idea anyway).
+  delete it.
 
 - The `scopeguard` crate also supports cleanup strategies via the
   [`Strategy`](https://docs.rs/scopeguard/latest/scopeguard/trait.Strategy.html)

src/idiomatic/leveraging-the-type-system/token-types/branded-02-phantomdata.md

@@ -72,7 +72,7 @@ fn main() {
   lifetimes have a common shorter lifetime (AKA being subtyped).
 
 - Note: This slide compiles, by the end of this slide it should only compile
-  when `subtyped_lifetimes` is commented out.
+  when `try_coerce_lifetimes` is commented out.
 
 - There are two important parts of this code:
   - The `impl for<'a>` bound on the closure passed to `lifetime_separator`.

src/idiomatic/leveraging-the-type-system/typestate-pattern.md

@@ -7,7 +7,7 @@ Copyright 2025 Google LLC
 SPDX-License-Identifier: CC-BY-4.0
 -->
 
-## Typestate Pattern: Problem
+# Typestate Pattern: Problem
 
 How can we ensure that only valid operations are allowed on a value based on its
 current state?

src/idiomatic/polymorphism/from-oop-to-rust/why-no-inheritance.md

@@ -57,8 +57,8 @@ impl SomeTrait for Data {
   interchangeably, without being able to specify a concrete type or if a type is
   identical to another.
 
-  For operations like equality, comparison this allows for comparison and
-  equality that throws and error or otherwise panics.
+  For operations like equality or comparison this allows for comparison and
+  equality that throws an error or otherwise panics.
 
 - Multiple sources of truth for what makes up a data structure and how it
   behaves: