Use nightly clippy to kill dead code/fix style (#12334)

- **Remove duplicated imports**
- **Remove unused field in `CompletionOptions`**
- **Remove unused struct in `nu-table`**
- **Clarify generic bounds**
- **Simplify a subtrait bound for `ExactSizeIterator`**
- **Use `unwrap_or_default`**
- **Use `Option` directly instead of empty string**
- **Elide unneeded clone in `to html`**

crates/nu-command/src/conversions/into/cell_path.rs

@@ -1,5 +1,5 @@
 use nu_engine::command_prelude::*;
-use nu_protocol::ast::{CellPath, PathMember};
+use nu_protocol::ast::PathMember;
 
 #[derive(Clone)]
 pub struct IntoCellPath;

crates/nu-command/src/conversions/into/duration.rs

@@ -1,9 +1,6 @@
 use nu_engine::command_prelude::*;
 use nu_parser::{parse_unit_value, DURATION_UNIT_GROUPS};
-use nu_protocol::{
-    ast::{CellPath, Expr},
-    Unit,
-};
+use nu_protocol::{ast::Expr, Unit};
 
 const NS_PER_SEC: i64 = 1_000_000_000;
 #[derive(Clone)]

crates/nu-command/src/default_context.rs

@@ -1,7 +1,4 @@
-use crate::{
-    help::{HelpAliases, HelpCommands, HelpEscapes, HelpExterns, HelpModules, HelpOperators},
-    *,
-};
+use crate::*;
 use nu_protocol::engine::{EngineState, StateWorkingSet};
 
 pub fn add_shell_command_context(mut engine_state: EngineState) -> EngineState {

crates/nu-command/src/filesystem/open.rs

@@ -6,9 +6,6 @@ use std::{io::BufReader, path::Path};
 #[cfg(feature = "sqlite")]
 use crate::database::SQLiteDatabase;
 
-#[cfg(feature = "sqlite")]
-use nu_protocol::IntoPipelineData;
-
 #[cfg(unix)]
 use std::os::unix::fs::PermissionsExt;
 

crates/nu-command/src/filters/find.rs

@@ -368,10 +368,9 @@ fn find_with_rest_and_highlight(
     let highlight_style =
         style_computer.compute("search_result", &Value::string("search result", span));
 
-    let cols_to_search_in_map = match call.get_flag(&engine_state, stack, "columns")? {
-        Some(cols) => cols,
-        None => vec![],
-    };
+    let cols_to_search_in_map: Vec<_> = call
+        .get_flag(&engine_state, stack, "columns")?
+        .unwrap_or_default();
 
     let cols_to_search_in_filter = cols_to_search_in_map.clone();
 

crates/nu-command/src/filters/skip/skip_.rs

@@ -1,7 +1,5 @@
 use nu_engine::command_prelude::*;
 
-use std::convert::TryInto;
-
 #[derive(Clone)]
 pub struct Skip;
 

crates/nu-command/src/stor/delete.rs

@@ -85,24 +85,22 @@ impl Command for StorDelete {
         let db = Box::new(SQLiteDatabase::new(std::path::Path::new(MEMORY_DB), None));
 
         if let Some(new_table_name) = table_name_opt {
-            let where_clause = match where_clause_opt {
-                Some(where_stmt) => where_stmt,
-                None => String::new(),
-            };
-
             if let Ok(conn) = db.open_connection() {
-                let sql_stmt = if where_clause.is_empty() {
-                    // We're deleting an entire table
-                    format!("DROP TABLE {}", new_table_name)
-                } else {
-                    // We're just deleting some rows
-                    let mut delete_stmt = format!("DELETE FROM {} ", new_table_name);
+                let sql_stmt = match where_clause_opt {
+                    None => {
+                        // We're deleting an entire table
+                        format!("DROP TABLE {}", new_table_name)
+                    }
+                    Some(where_clause) => {
+                        // We're just deleting some rows
+                        let mut delete_stmt = format!("DELETE FROM {} ", new_table_name);
 
-                    // Yup, this is a bit janky, but I'm not sure a better way to do this without having
-                    // --and and --or flags as well as supporting ==, !=, <>, is null, is not null, etc.
-                    // and other sql syntax. So, for now, just type a sql where clause as a string.
-                    delete_stmt.push_str(&format!("WHERE {}", where_clause));
-                    delete_stmt
+                        // Yup, this is a bit janky, but I'm not sure a better way to do this without having
+                        // --and and --or flags as well as supporting ==, !=, <>, is null, is not null, etc.
+                        // and other sql syntax. So, for now, just type a sql where clause as a string.
+                        delete_stmt.push_str(&format!("WHERE {}", where_clause));
+                        delete_stmt
+                    }
                 };
 
                 // dbg!(&sql_stmt);

crates/nu-command/src/viewers/table.rs

@@ -919,7 +919,7 @@ fn get_abbriviated_dummy(head: &[Value], tail: &VecDeque<Value>) -> Value {
     }
 }
 
-fn is_record_list<'a>(mut batch: impl Iterator<Item = &'a Value> + ExactSizeIterator) -> bool {
+fn is_record_list<'a>(mut batch: impl ExactSizeIterator<Item = &'a Value>) -> bool {
     batch.len() > 0 && batch.all(|value| matches!(value, Value::Record { .. }))
 }