Merge 'Random cleanups' from Pekka Enberg

Build got pretty noisy recently, let's clean up some things.

Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>

Closes #559

cli/app.rs

@@ -526,7 +526,7 @@ impl Limbo {
                             break;
                         }
                         Ok(StepResult::Busy) => {
-                            self.writeln("database is busy");
+                            let _ = self.writeln("database is busy");
                             break;
                         }
                         Err(err) => {
@@ -565,7 +565,7 @@ impl Limbo {
                             Ok(StepResult::Interrupt) => break,
                             Ok(StepResult::Done) => break,
                             Ok(StepResult::Busy) => {
-                                self.writeln("database is busy");
+                                let _ = self.writeln("database is busy");
                                 break;
                             }
                             Err(err) => {
@@ -619,7 +619,7 @@ impl Limbo {
                         StepResult::Interrupt => break,
                         StepResult::Done => break,
                         StepResult::Busy => {
-                            self.writeln("database is busy");
+                            let _ = self.writeln("database is busy");
                             break;
                         }
                     }
@@ -676,7 +676,7 @@ impl Limbo {
                         StepResult::Interrupt => break,
                         StepResult::Done => break,
                         StepResult::Busy => {
-                            self.writeln("database is busy");
+                            let _ = self.writeln("database is busy");
                             break;
                         }
                     }

core/storage/wal.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 use std::sync::atomic::{AtomicU32, Ordering};
 use std::sync::RwLock;
 use std::{cell::RefCell, rc::Rc, sync::Arc};
@@ -16,7 +16,6 @@ use crate::{Completion, Page};
 use self::sqlite3_ondisk::{checksum_wal, PageContent, WAL_MAGIC_BE, WAL_MAGIC_LE};
 
 use super::buffer_pool::BufferPool;
-use super::page_cache::PageCacheKey;
 use super::pager::{PageRef, Pager};
 use super::sqlite3_ondisk::{self, begin_write_btree_page, WalHeader};
 

core/translate/mod.rs

@@ -369,7 +369,6 @@ fn update_pragma(
             query_pragma("journal_mode", header, program)?;
             Ok(())
         }
-        _ => todo!("pragma `{name}`"),
     }
 }
 
@@ -396,9 +395,6 @@ fn query_pragma(
                 dest: register,
             });
         }
-        _ => {
-            todo!("pragma `{name}`");
-        }
     }
 
     program.emit_insn(Insn::ResultRow {

core/translate/planner.rs

@@ -1,8 +1,5 @@
-use super::{
-    optimizer::Optimizable,
-    plan::{
-        Aggregate, BTreeTableReference, Direction, GroupBy, Plan, ResultSetColumn, SourceOperator,
-    },
+use super::plan::{
+    Aggregate, BTreeTableReference, Direction, GroupBy, Plan, ResultSetColumn, SourceOperator,
 };
 use crate::{
     function::Func,
@@ -267,7 +264,7 @@ pub fn prepare_select_plan<'a>(schema: &Schema, select: ast::Select) -> Result<P
             columns,
             from,
             where_clause,
-            mut group_by,
+            group_by,
             ..
         } => {
             let col_count = columns.len();

core/vdbe/builder.rs

@@ -59,10 +59,6 @@ impl ProgramBuilder {
         reg
     }
 
-    pub fn next_free_register(&self) -> usize {
-        self.next_free_register
-    }
-
     pub fn alloc_cursor_id(
         &mut self,
         table_identifier: Option<String>,

core/vdbe/explain.rs

@@ -1,5 +1,4 @@
 use super::{Insn, InsnReference, OwnedValue, Program};
-use crate::types::LimboText;
 use std::rc::Rc;
 
 pub fn insn_to_str(