Apply suggestions from code review

Co-Authored-By: Niko Matsakis <niko@alum.mit.edu>

book/src/common_patterns.md

@@ -1,19 +1,19 @@
 # Common patterns
 
-## On Demnd (Lazy) Inputs
+## On Demand (Lazy) Inputs
 
 Salsa input quries work best if you can easily provide all of the inputs upfront.
 However sometimes the set of inputs is not known beforehand.
 
 A typical example is reading files from disk.
-While it is possible to eagarly scan a particular directory and create an in-memory file tree in a salsa input query, a more straight forward approach is to read the files lazily.
+While it is possible to eagerly scan a particular directory and create an in-memory file tree in a salsa input query, a more straight-forward approach is to read the files lazily.
 That is, when someone requests the text of a file for the first time:
 
 1. Read the file from disk and cache it.
 2. Setup a file-system watcher for this path.
-3. Innvalidate the cached file once the watcher sends a change notification.
+3. Invalidate the cached file once the watcher sends a change notification.
 
-This is possible to achive in salsa, using a derived query and `report_synthetic_read` and `invalidate` queries.
+This is possible to achieve in salsa, using a derived query and `report_synthetic_read` and `invalidate` queries.
 The setup looks roughtly like this:
 
 ```rust,ignore

src/lib.rs

@@ -559,7 +559,7 @@ where
     /// This causes salsa to re-execute the query function on the next access to
     /// the query, even if all dependencies are up to date.
     ///
-    /// This is most commonly used for queries with zero inputs.
+    /// This is most commonly used for invaliding on-demand inputs; see the [Salsa Book](https://salsa-rs.github.io/salsa/) for more information.
     pub fn invalidate(&self, key: &Q::Key)
     where
         Q::Storage: plumbing::DerivedQueryStorageOps<DB, Q>,

src/runtime.rs

@@ -396,10 +396,9 @@ where
             .report_untracked_read(self.current_revision());
     }
 
-    /// Fores the durability of the current query to at most `durability`.
+    /// Acts as though the current query had read an input with the given durability; this will force the current query's durability to be at most `durability`.
     ///
-    /// This is mostly useful to lower durability level of derived queries with
-    /// zero inputs.
+    /// This is mostly useful to control the durability level for on-demand inputs, as described in [the salsa book](https://salsa-rs.github.io/salsa/).
     pub fn report_synthetic_read(&self, durability: Durability) {
         self.local_state
             .report_synthetic_read(durability);