Fix some typos.

lib/filecheck/src/error.rs

@@ -19,7 +19,7 @@ pub enum Error {
     UndefVariable(String),
     /// A pattern contains a back-reference to a variable that was defined in the same pattern.
     ///
-    /// For example, `check: Hello $(world=.*) $world`. Backreferences are not support. Often the
+    /// For example, `check: Hello $(world=.*) $world`. Backreferences are not supported. Often the
     /// desired effect can be achieved with the `sameln` check:
     ///
     /// ```text

lib/filecheck/src/pattern.rs

@@ -42,7 +42,7 @@ pub enum Part {
 }
 
 impl Part {
-    /// Get the variabled referenced by this part, if any.
+    /// Get the variable referenced by this part, if any.
     pub fn ref_var(&self) -> Option<&str> {
         match *self {
             Part::Var(ref var) |
@@ -217,10 +217,10 @@ impl Pattern {
 }
 
 /// Compute the length of a regular expression terminated by `)` or `}`.
-/// Handle nested and escaped parentheses in the rx, but don't actualy parse it.
+/// Handle nested and escaped parentheses in the rx, but don't actually parse it.
 /// Return the position of the terminating brace or the length of the string.
 fn regex_prefix(s: &str) -> usize {
-    // The prevous char was a backslash.
+    // The previous char was a backslash.
     let mut escape = false;
     // State around parsing charsets.
     enum State {

lib/filecheck/src/variable.rs

@@ -3,7 +3,7 @@ use std::borrow::Cow;
 /// A variable name is one or more ASCII alphanumerical characters, including underscore.
 /// Note that numerical variable names like `$45` are allowed too.
 ///
-/// Try to parse a variable name from the begining of `s`.
+/// Try to parse a variable name from the beginning of `s`.
 /// Return the index of the character following the varname.
 /// This returns 0 if `s` doesn't have a prefix that is a variable name.
 pub fn varname_prefix(s: &str) -> usize {