add tests for #3057.

Fixes #3057

tests/ui/similar_names.rs

@@ -0,0 +1,24 @@
+#![feature(tool_lints)]
+#![warn(clippy::similar_names)]
+
+// false positive (#3057)
+// would claim total_reg_src_size and total_size and
+// numb_reg_src_checkouts and total_bin_size are similar
+#[derive(Debug, Clone)]
+pub(crate) struct DirSizes {
+    pub(crate) total_size: u64,                // total size of cargo root dir
+    pub(crate) numb_bins: u64,                 // number of binaries found
+    pub(crate) total_bin_size: u64,            // total size of binaries found
+    pub(crate) total_reg_size: u64,            // registry size
+    pub(crate) total_git_db_size: u64,         // size of bare repos and checkouts combined
+    pub(crate) total_git_repos_bare_size: u64, // git db size
+    pub(crate) numb_git_repos_bare_repos: u64, // number of cloned repos
+    pub(crate) numb_git_checkouts: u64,        // number of checked out repos
+    pub(crate) total_git_chk_size: u64,        // git checkout size
+    pub(crate) total_reg_cache_size: u64,      // registry cache size
+    pub(crate) total_reg_src_size: u64,        // registry sources size
+    pub(crate) numb_reg_cache_entries: u64,    // number of source archives
+    pub(crate) numb_reg_src_checkouts: u64,    // number of source checkouts
+}
+
+fn main() {}