Use implicit capture syntax in format_args

This updates the standard library's documentation to use the new syntax. The
documentation is worthwhile to update as it should be more idiomatic
(particularly for features like this, which are nice for users to get acquainted
with). The general codebase is likely more hassle than benefit to update: it'll
hurt git blame, and generally updates can be done by folks updating the code if
(and when) that makes things more readable with the new format.

A few places in the compiler and library code are updated (mostly just due to
already having been done when this commit was first authored).

library/std/src/error.rs

@@ -96,7 +96,7 @@ pub trait Error: Debug + Display {
     /// fn main() {
     ///     match get_super_error() {
     ///         Err(e) => {
-    ///             println!("Error: {}", e);
+    ///             println!("Error: {e}");
     ///             println!("Caused by: {}", e.source().unwrap());
     ///         }
     ///         _ => println!("No error"),
@@ -139,7 +139,7 @@ pub trait Error: Debug + Display {
     /// ```
     /// if let Err(e) = "xc".parse::<u32>() {
     ///     // Print `e` itself, no need for description().
-    ///     eprintln!("Error: {}", e);
+    ///     eprintln!("Error: {e}");
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1074,7 +1074,7 @@ impl<E> Report<E> {
     ///
     /// let error = SuperError { source: SuperErrorSideKick };
     /// let report = Report::new(error).pretty(true);
-    /// eprintln!("Error: {:?}", report);
+    /// eprintln!("Error: {report:?}");
     /// ```
     ///
     /// This example produces the following output:
@@ -1135,7 +1135,7 @@ impl<E> Report<E> {
     /// let source = SuperErrorSideKick { source };
     /// let error = SuperError { source };
     /// let report = Report::new(error).pretty(true);
-    /// eprintln!("Error: {:?}", report);
+    /// eprintln!("Error: {report:?}");
     /// ```
     ///
     /// This example produces the following output:
@@ -1210,7 +1210,7 @@ impl<E> Report<E> {
     /// let source = SuperErrorSideKick::new();
     /// let error = SuperError { source };
     /// let report = Report::new(error).pretty(true).show_backtrace(true);
-    /// eprintln!("Error: {:?}", report);
+    /// eprintln!("Error: {report:?}");
     /// ```
     ///
     /// This example produces something similar to the following output:
@@ -1267,7 +1267,7 @@ where
         let sources = self.error.source().into_iter().flat_map(<dyn Error>::chain);
 
         for cause in sources {
-            write!(f, ": {}", cause)?;
+            write!(f, ": {cause}")?;
         }
 
         Ok(())
@@ -1278,7 +1278,7 @@ where
     fn fmt_multiline(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let error = &self.error;
 
-        write!(f, "{}", error)?;
+        write!(f, "{error}")?;
 
         if let Some(cause) = error.source() {
             write!(f, "\n\nCaused by:")?;
@@ -1289,9 +1289,9 @@ where
                 writeln!(f)?;
                 let mut indented = Indented { inner: f };
                 if multiple {
-                    write!(indented, "{: >4}: {}", ind, error)?;
+                    write!(indented, "{ind: >4}: {error}")?;
                 } else {
-                    write!(indented, "      {}", error)?;
+                    write!(indented, "      {error}")?;
                 }
             }
         }
@@ -1333,7 +1333,7 @@ impl Report<Box<dyn Error>> {
         let sources = self.error.source().into_iter().flat_map(<dyn Error>::chain);
 
         for cause in sources {
-            write!(f, ": {}", cause)?;
+            write!(f, ": {cause}")?;
         }
 
         Ok(())
@@ -1344,7 +1344,7 @@ impl Report<Box<dyn Error>> {
     fn fmt_multiline(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         let error = &self.error;
 
-        write!(f, "{}", error)?;
+        write!(f, "{error}")?;
 
         if let Some(cause) = error.source() {
             write!(f, "\n\nCaused by:")?;
@@ -1355,9 +1355,9 @@ impl Report<Box<dyn Error>> {
                 writeln!(f)?;
                 let mut indented = Indented { inner: f };
                 if multiple {
-                    write!(indented, "{: >4}: {}", ind, error)?;
+                    write!(indented, "{ind: >4}: {error}")?;
                 } else {
-                    write!(indented, "      {}", error)?;
+                    write!(indented, "      {error}")?;
                 }
             }
         }