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+### What it does
+Detect when a variable is not inlined in a format string,
+and suggests to inline it.
+
+### Why is this bad?
+Non-inlined code is slightly more difficult to read and understand,
+as it requires arguments to be matched against the format string.
+The inlined syntax, where allowed, is simpler.
+
+### Example
+```
+format!("{}", var);
+format!("{v:?}", v = var);
+format!("{0} {0}", var);
+format!("{0:1$}", var, width);
+format!("{:.*}", prec, var);
+```
+Use instead:
+```
+format!("{var}");
+format!("{var:?}");
+format!("{var} {var}");
+format!("{var:width$}");
+format!("{var:.prec$}");
+```
+
+### Known Problems
+
+There may be a false positive if the format string is expanded from certain proc macros:
+
+```
+println!(indoc!("{}"), var);
+```
+
+If a format string contains a numbered argument that cannot be inlined
+nothing will be suggested, e.g. `println!("{0}={1}", var, 1+2)`.
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