Add HashMap to std prelude

* Fix `HashMap` redundantly import errors
* Replace HashMap by BTreeMap in tests suggested by Jonas

Author: tesuji

src/doc/rustc/src/lints/listing/warn-by-default.md

@@ -796,17 +796,17 @@ This lint detects imports that are never used. Some
 example code that triggers this lint:
 
 ```rust
-use std::collections::HashMap;
+use std::collections::BTreeMap;
 ```
 
 This will produce:
 
 ```text
-warning: unused import: `std::collections::HashMap`
+warning: unused import: `std::collections::BTreeMap`
  --> src/main.rs:1:5
   |
-1 | use std::collections::HashMap;
-  |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+1 | use std::collections::BTreeMap;
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
 ```
 

src/libcore/cell.rs

@@ -68,7 +68,6 @@
 //!
 //! ```
 //! use std::cell::{RefCell, RefMut};
-//! use std::collections::HashMap;
 //! use std::rc::Rc;
 //!
 //! fn main() {

src/libcore/hash/mod.rs

@@ -478,7 +478,6 @@ pub trait BuildHasher {
 /// [`HashMap`]:
 ///
 /// ```
-/// use std::collections::HashMap;
 /// use std::hash::{BuildHasherDefault, Hasher};
 ///
 /// #[derive(Default)]

src/libcore/option.rs

@@ -993,7 +993,6 @@ impl<T: fmt::Debug> Option<T> {
     /// ```
     /// #![feature(option_expect_none)]
     ///
-    /// use std::collections::HashMap;
     /// let mut squares = HashMap::new();
     /// for i in -10..=10 {
     ///     // This will not panic, since all keys are unique.
@@ -1004,7 +1003,6 @@ impl<T: fmt::Debug> Option<T> {
     /// ```{.should_panic}
     /// #![feature(option_expect_none)]
     ///
-    /// use std::collections::HashMap;
     /// let mut sqrts = HashMap::new();
     /// for i in -10..=10 {
     ///     // This will panic, since both negative and positive `i` will
@@ -1035,7 +1033,6 @@ impl<T: fmt::Debug> Option<T> {
     /// ```
     /// #![feature(option_unwrap_none)]
     ///
-    /// use std::collections::HashMap;
     /// let mut squares = HashMap::new();
     /// for i in -10..=10 {
     ///     // This will not panic, since all keys are unique.
@@ -1046,7 +1043,6 @@ impl<T: fmt::Debug> Option<T> {
     /// ```{.should_panic}
     /// #![feature(option_unwrap_none)]
     ///
-    /// use std::collections::HashMap;
     /// let mut sqrts = HashMap::new();
     /// for i in -10..=10 {
     ///     // This will panic, since both negative and positive `i` will

src/librustc_data_structures/owning_ref/tests.rs

@@ -4,7 +4,6 @@ mod owning_ref {
     use std::cmp::{PartialEq, Ord, PartialOrd, Ordering};
     use std::hash::{Hash, Hasher};
     use std::collections::hash_map::DefaultHasher;
-    use std::collections::HashMap;
     use std::rc::Rc;
 
     #[derive(Debug, PartialEq)]
@@ -379,7 +378,6 @@ mod owning_ref_mut {
     use std::cmp::{PartialEq, Ord, PartialOrd, Ordering};
     use std::hash::{Hash, Hasher};
     use std::collections::hash_map::DefaultHasher;
-    use std::collections::HashMap;
 
     #[derive(Debug, PartialEq)]
     struct Example(u32, String, [u8; 3]);

src/librustc_data_structures/sync.rs

@@ -17,7 +17,6 @@
 //! `rustc_erase_owner!` erases a OwningRef owner into Erased or Erased + Send + Sync
 //! depending on the value of cfg!(parallel_compiler).
 
-use std::collections::HashMap;
 use std::hash::{Hash, BuildHasher};
 use std::marker::PhantomData;
 use std::ops::{Deref, DerefMut};

src/librustc_resolve/error_codes.rs

@@ -1250,7 +1250,7 @@ An undeclared type or module was used.
 Erroneous code example:
 
 ```compile_fail,E0433
-let map = HashMap::new();
+let map = BTreeMap::new();
 // error: failed to resolve: use of undeclared type or module `HashMap`
 ```
 
@@ -1259,8 +1259,8 @@ forget to import it:
 
 
 ```
-use std::collections::HashMap; // HashMap has been imported.
-let map: HashMap<u32, u32> = HashMap::new(); // So it can be used!
+use std::collections::BTreeMap; // BTreeMap has been imported.
+let map: BTreeMap<u32, u32> = BTreeMap::new(); // So it can be used!
 ```
 "##,
 

src/libserialize/tests/json.rs

@@ -849,7 +849,6 @@ fn test_as_null(){
 #[test]
 fn test_encode_hashmap_with_numeric_key() {
     use std::str::from_utf8;
-    use std::collections::HashMap;
     let mut hm: HashMap<usize, bool> = HashMap::new();
     hm.insert(1, true);
     let mut mem_buf = Vec::new();
@@ -864,7 +863,6 @@ fn test_encode_hashmap_with_numeric_key() {
 #[test]
 fn test_prettyencode_hashmap_with_numeric_key() {
     use std::str::from_utf8;
-    use std::collections::HashMap;
     let mut hm: HashMap<usize, bool> = HashMap::new();
     hm.insert(1, true);
     let mut mem_buf = Vec::new();
@@ -930,7 +928,6 @@ fn test_prettyencoder_indent_level_param() {
 
 #[test]
 fn test_hashmap_with_enum_key() {
-    use std::collections::HashMap;
     #[derive(RustcEncodable, Eq, Hash, PartialEq, RustcDecodable, Debug)]
     enum Enum {
         Foo,
@@ -947,7 +944,6 @@ fn test_hashmap_with_enum_key() {
 
 #[test]
 fn test_hashmap_with_numeric_key_can_handle_double_quote_delimited_key() {
-    use std::collections::HashMap;
     let json_str = "{\"1\":true}";
     let json_obj = match from_str(json_str) {
         Err(_) => panic!("Unable to parse json_str: {:?}", json_str),
@@ -959,7 +955,6 @@ fn test_hashmap_with_numeric_key_can_handle_double_quote_delimited_key() {
 
 #[test]
 fn test_hashmap_with_numeric_key_will_error_with_string_keys() {
-    use std::collections::HashMap;
     let json_str = "{\"a\":true}";
     let json_obj = match from_str(json_str) {
         Err(_) => panic!("Unable to parse json_str: {:?}", json_str),
@@ -1267,7 +1262,6 @@ fn test_to_json() {
 
 #[test]
 fn test_encode_hashmap_with_arbitrary_key() {
-    use std::collections::HashMap;
     #[derive(PartialEq, Eq, Hash, RustcEncodable)]
     struct ArbitraryType(usize);
     let mut hm: HashMap<ArbitraryType, bool> = HashMap::new();

src/libserialize/tests/opaque.rs

@@ -263,7 +263,6 @@ fn test_sequence() {
 
 #[test]
 fn test_hash_map() {
-    use std::collections::HashMap;
     let mut map = HashMap::new();
     for i in -100i64..100i64 {
         map.insert(i * 100000, i * 10000);