Extract single_match_else UI test

There's only one test currently.
I also updated the lint doc with a 'good' example and changed the lint
help text a bit.

cc #2038

diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs
index dedf9a16b356d215c5cf0b2f452468ce70be8318..3ef8d5348611c8677bef6ee7a3cbab8d910e4c8a 100644 (file)
--- a/clippy_lints/src/matches.rs
+++ b/clippy_lints/src/matches.rs
@@ -45,7 +45,7 @@
     "a match statement with a single nontrivial arm (i.e. where the other arm is `_ => {}`) instead of `if let`"
 }
 
-/// **What it does:** Checks for matches with a two arms where an `if let` will
+/// **What it does:** Checks for matches with a two arms where an `if let else` will
 /// usually suffice.
 ///
 /// **Why is this bad?** Just readability – `if let` nests less than a `match`.
@@ -53,16 +53,29 @@
 /// **Known problems:** Personal style preferences may differ.
 ///
 /// **Example:**
+///
+/// Using `match`:
+///
 /// ```rust
 /// match x {
 ///     Some(ref foo) => bar(foo),
 ///     _ => bar(other_ref),
 /// }
 /// ```
+///
+/// Using `if let` with `else`:
+///
+/// ```rust
+/// if let Some(ref foo) = x {
+///     bar(foo);
+/// } else {
+///     bar(other_ref);
+/// }
+/// ```
 declare_clippy_lint! {
     pub SINGLE_MATCH_ELSE,
     pedantic,
-    "a match statement with a two arms where the second arm's pattern is a wildcard instead of `if let`"
+    "a match statement with a two arms where the second arm's pattern is a placeholder instead of a specific match pattern"
 }
 
 /// **What it does:** Checks for matches where all arms match a reference,

diff --git a/tests/ui/matches.rs b/tests/ui/matches.rs
index c7630b0533d2e9e3b9620ee11dec5764a01f20d5..e5b8f6f4c1cf6a489c4e2a9054bfa33989a70e07 100644 (file)
--- a/tests/ui/matches.rs
+++ b/tests/ui/matches.rs
@@ -14,26 +14,12 @@
 
 #![warn(clippy::all)]
 #![allow(unused, clippy::redundant_pattern_matching)]
-#![warn(clippy::single_match_else, clippy::match_same_arms)]
+#![warn(clippy::match_same_arms)]
 
-enum ExprNode {
-    ExprAddrOf,
-    Butterflies,
-    Unicorns,
-}
-
-static NODE: ExprNode = ExprNode::Unicorns;
 
 fn dummy() {
 }
 
-fn unwrap_addr() -> Option<&'static ExprNode> {
-    match ExprNode::Butterflies {
-        ExprNode::ExprAddrOf => Some(&NODE),
-        _ => { let x = 5; None },
-    }
-}
-
 fn ref_pats() {
     {
         let v = &Some(0);

diff --git a/tests/ui/matches.stderr b/tests/ui/matches.stderr
index aebb166d3bcd41d8341732aab51031af1b892819..53e61efa83a518bfbd379ac6daa5375401ea6918 100644 (file)
--- a/tests/ui/matches.stderr
+++ b/tests/ui/matches.stderr
@@ -1,302 +1,282 @@
-error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
-  --> $DIR/matches.rs:31:5
-   |
-31 | /     match ExprNode::Butterflies {
-32 | |         ExprNode::ExprAddrOf => Some(&NODE),
-33 | |         _ => { let x = 5; None },
-34 | |     }
-   | |_____^ help: try this: `if let ExprNode::ExprAddrOf = ExprNode::Butterflies { Some(&NODE) } else { let x = 5; None }`
-   |
-   = note: `-D clippy::single-match-else` implied by `-D warnings`
-
 error: you don't need to add `&` to all patterns
-  --> $DIR/matches.rs:40:9
+  --> $DIR/matches.rs:26:9
    |
-40 | /         match v {
-41 | |             &Some(v) => println!("{:?}", v),
-42 | |             &None => println!("none"),
-43 | |         }
+26 | /         match v {
+27 | |             &Some(v) => println!("{:?}", v),
+28 | |             &None => println!("none"),
+29 | |         }
    | |_________^
    |
    = note: `-D clippy::match-ref-pats` implied by `-D warnings`
 help: instead of prefixing all patterns with `&`, you can dereference the expression
    |
-40 |         match *v {
-41 |             Some(v) => println!("{:?}", v),
-42 |             None => println!("none"),
+26 |         match *v {
+27 |             Some(v) => println!("{:?}", v),
+28 |             None => println!("none"),
    |
 
-error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
-  --> $DIR/matches.rs:50:5
-   |
-50 | /     match tup {
-51 | |         &(v, 1) => println!("{}", v),
-52 | |         _ => println!("none"),
-53 | |     }
-   | |_____^ help: try this: `if let &(v, 1) = tup { println!("{}", v) } else { println!("none") }`
-
 error: you don't need to add `&` to all patterns
-  --> $DIR/matches.rs:50:5
+  --> $DIR/matches.rs:36:5
    |
-50 | /     match tup {
-51 | |         &(v, 1) => println!("{}", v),
-52 | |         _ => println!("none"),
-53 | |     }
+36 | /     match tup {
+37 | |         &(v, 1) => println!("{}", v),
+38 | |         _ => println!("none"),
+39 | |     }
    | |_____^
 help: instead of prefixing all patterns with `&`, you can dereference the expression
    |
-50 |     match *tup {
-51 |         (v, 1) => println!("{}", v),
+36 |     match *tup {
+37 |         (v, 1) => println!("{}", v),
    |
 
 error: you don't need to add `&` to both the expression and the patterns
-  --> $DIR/matches.rs:56:5
+  --> $DIR/matches.rs:42:5
    |
-56 | /     match &w {
-57 | |         &Some(v) => println!("{:?}", v),
-58 | |         &None => println!("none"),
-59 | |     }
+42 | /     match &w {
+43 | |         &Some(v) => println!("{:?}", v),
+44 | |         &None => println!("none"),
+45 | |     }
    | |_____^
 help: try
    |
-56 |     match w {
-57 |         Some(v) => println!("{:?}", v),
-58 |         None => println!("none"),
+42 |     match w {
+43 |         Some(v) => println!("{:?}", v),
+44 |         None => println!("none"),
    |
 
 error: you don't need to add `&` to all patterns
-  --> $DIR/matches.rs:67:5
+  --> $DIR/matches.rs:53:5
    |
-67 | /     if let &None = a {
-68 | |         println!("none");
-69 | |     }
+53 | /     if let &None = a {
+54 | |         println!("none");
+55 | |     }
    | |_____^
 help: instead of prefixing all patterns with `&`, you can dereference the expression
    |
-67 |     if let None = *a {
+53 |     if let None = *a {
    |            ^^^^   ^^
 
 error: you don't need to add `&` to both the expression and the patterns
-  --> $DIR/matches.rs:72:5
+  --> $DIR/matches.rs:58:5
    |
-72 | /     if let &None = &b {
-73 | |         println!("none");
-74 | |     }
+58 | /     if let &None = &b {
+59 | |         println!("none");
+60 | |     }
    | |_____^
 help: try
    |
-72 |     if let None = b {
+58 |     if let None = b {
    |            ^^^^   ^
 
 error: Err(_) will match all errors, maybe not a good idea
-  --> $DIR/matches.rs:83:9
+  --> $DIR/matches.rs:69:9
    |
-83 |         Err(_) => panic!("err")
+69 |         Err(_) => panic!("err")
    |         ^^^^^^
    |
    = note: `-D clippy::match-wild-err-arm` implied by `-D warnings`
    = note: to remove this warning, match each error separately or use unreachable macro
 
 error: this `match` has identical arm bodies
-  --> $DIR/matches.rs:82:18
+  --> $DIR/matches.rs:68:18
    |
-82 |         Ok(_) => println!("ok"),
+68 |         Ok(_) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    |
    = note: `-D clippy::match-same-arms` implied by `-D warnings`
 note: same as this
-  --> $DIR/matches.rs:81:18
+  --> $DIR/matches.rs:67:18
    |
-81 |         Ok(3) => println!("ok"),
+67 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-  --> $DIR/matches.rs:81:18
+  --> $DIR/matches.rs:67:18
    |
-81 |         Ok(3) => println!("ok"),
+67 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: Err(_) will match all errors, maybe not a good idea
-  --> $DIR/matches.rs:89:9
+  --> $DIR/matches.rs:75:9
    |
-89 |         Err(_) => {panic!()}
+75 |         Err(_) => {panic!()}
    |         ^^^^^^
    |
    = note: to remove this warning, match each error separately or use unreachable macro
 
 error: this `match` has identical arm bodies
-  --> $DIR/matches.rs:88:18
+  --> $DIR/matches.rs:74:18
    |
-88 |         Ok(_) => println!("ok"),
+74 |         Ok(_) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    |
 note: same as this
-  --> $DIR/matches.rs:87:18
+  --> $DIR/matches.rs:73:18
    |
-87 |         Ok(3) => println!("ok"),
+73 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-  --> $DIR/matches.rs:87:18
+  --> $DIR/matches.rs:73:18
    |
-87 |         Ok(3) => println!("ok"),
+73 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: Err(_) will match all errors, maybe not a good idea
-  --> $DIR/matches.rs:95:9
+  --> $DIR/matches.rs:81:9
    |
-95 |         Err(_) => {panic!();}
+81 |         Err(_) => {panic!();}
    |         ^^^^^^
    |
    = note: to remove this warning, match each error separately or use unreachable macro
 
 error: this `match` has identical arm bodies
-  --> $DIR/matches.rs:94:18
+  --> $DIR/matches.rs:80:18
    |
-94 |         Ok(_) => println!("ok"),
+80 |         Ok(_) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    |
 note: same as this
-  --> $DIR/matches.rs:93:18
+  --> $DIR/matches.rs:79:18
    |
-93 |         Ok(3) => println!("ok"),
+79 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-  --> $DIR/matches.rs:93:18
+  --> $DIR/matches.rs:79:18
    |
-93 |         Ok(3) => println!("ok"),
+79 |         Ok(3) => println!("ok"),
    |                  ^^^^^^^^^^^^^^
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:101:18
-    |
-101 |         Ok(_) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
-    |
+  --> $DIR/matches.rs:87:18
+   |
+87 |         Ok(_) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
+   |
 note: same as this
-   --> $DIR/matches.rs:100:18
-    |
-100 |         Ok(3) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
+  --> $DIR/matches.rs:86:18
+   |
+86 |         Ok(3) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-   --> $DIR/matches.rs:100:18
-    |
-100 |         Ok(3) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
-    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+  --> $DIR/matches.rs:86:18
+   |
+86 |         Ok(3) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
+   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:108:18
-    |
-108 |         Ok(_) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
-    |
+  --> $DIR/matches.rs:94:18
+   |
+94 |         Ok(_) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
+   |
 note: same as this
-   --> $DIR/matches.rs:107:18
-    |
-107 |         Ok(3) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
+  --> $DIR/matches.rs:93:18
+   |
+93 |         Ok(3) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-   --> $DIR/matches.rs:107:18
-    |
-107 |         Ok(3) => println!("ok"),
-    |                  ^^^^^^^^^^^^^^
-    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+  --> $DIR/matches.rs:93:18
+   |
+93 |         Ok(3) => println!("ok"),
+   |                  ^^^^^^^^^^^^^^
+   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:114:18
+   --> $DIR/matches.rs:100:18
     |
-114 |         Ok(_) => println!("ok"),
+100 |         Ok(_) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     |
 note: same as this
-   --> $DIR/matches.rs:113:18
+   --> $DIR/matches.rs:99:18
     |
-113 |         Ok(3) => println!("ok"),
+99  |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-   --> $DIR/matches.rs:113:18
+   --> $DIR/matches.rs:99:18
     |
-113 |         Ok(3) => println!("ok"),
+99  |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:120:18
+   --> $DIR/matches.rs:106:18
     |
-120 |         Ok(_) => println!("ok"),
+106 |         Ok(_) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     |
 note: same as this
-   --> $DIR/matches.rs:119:18
+   --> $DIR/matches.rs:105:18
     |
-119 |         Ok(3) => println!("ok"),
+105 |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-   --> $DIR/matches.rs:119:18
+   --> $DIR/matches.rs:105:18
     |
-119 |         Ok(3) => println!("ok"),
+105 |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:141:29
+   --> $DIR/matches.rs:127:29
     |
-141 |         (Ok(_), Some(x)) => println!("ok {}", x),
+127 |         (Ok(_), Some(x)) => println!("ok {}", x),
     |                             ^^^^^^^^^^^^^^^^^^^^
     |
 note: same as this
-   --> $DIR/matches.rs:140:29
+   --> $DIR/matches.rs:126:29
     |
-140 |         (Ok(x), Some(_)) => println!("ok {}", x),
+126 |         (Ok(x), Some(_)) => println!("ok {}", x),
     |                             ^^^^^^^^^^^^^^^^^^^^
 note: consider refactoring into `(Ok(x), Some(_)) | (Ok(_), Some(x))`
-   --> $DIR/matches.rs:140:29
+   --> $DIR/matches.rs:126:29
     |
-140 |         (Ok(x), Some(_)) => println!("ok {}", x),
+126 |         (Ok(x), Some(_)) => println!("ok {}", x),
     |                             ^^^^^^^^^^^^^^^^^^^^
     = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: this `match` has identical arm bodies
-   --> $DIR/matches.rs:156:18
+   --> $DIR/matches.rs:142:18
     |
-156 |         Ok(_) => println!("ok"),
+142 |         Ok(_) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     |
 note: same as this
-   --> $DIR/matches.rs:155:18
+   --> $DIR/matches.rs:141:18
     |
-155 |         Ok(3) => println!("ok"),
+141 |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
 note: consider refactoring into `Ok(3) | Ok(_)`
-   --> $DIR/matches.rs:155:18
+   --> $DIR/matches.rs:141:18
     |
-155 |         Ok(3) => println!("ok"),
+141 |         Ok(3) => println!("ok"),
     |                  ^^^^^^^^^^^^^^
     = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: use as_ref() instead
-   --> $DIR/matches.rs:163:33
+   --> $DIR/matches.rs:149:33
     |
-163 |       let borrowed: Option<&()> = match owned {
+149 |       let borrowed: Option<&()> = match owned {
     |  _________________________________^
-164 | |         None => None,
-165 | |         Some(ref v) => Some(v),
-166 | |     };
+150 | |         None => None,
+151 | |         Some(ref v) => Some(v),
+152 | |     };
     | |_____^ help: try this: `owned.as_ref()`
     |
     = note: `-D clippy::match-as-ref` implied by `-D warnings`
 
 error: use as_mut() instead
-   --> $DIR/matches.rs:169:39
+   --> $DIR/matches.rs:155:39
     |
-169 |       let borrow_mut: Option<&mut ()> = match mut_owned {
+155 |       let borrow_mut: Option<&mut ()> = match mut_owned {
     |  _______________________________________^
-170 | |         None => None,
-171 | |         Some(ref mut v) => Some(v),
-172 | |     };
+156 | |         None => None,
+157 | |         Some(ref mut v) => Some(v),
+158 | |     };
     | |_____^ help: try this: `mut_owned.as_mut()`
 
-error: aborting due to 21 previous errors
+error: aborting due to 19 previous errors
 

diff --git a/tests/ui/single_match_else.rs b/tests/ui/single_match_else.rs
new file mode 100644 (file)
index 0000000..a7c28c5
--- /dev/null
+++ b/tests/ui/single_match_else.rs
@@ -0,0 +1,27 @@
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![warn(clippy::single_match_else)]
+
+enum ExprNode {
+    ExprAddrOf,
+    Butterflies,
+    Unicorns,
+}
+
+static NODE: ExprNode = ExprNode::Unicorns;
+
+fn unwrap_addr() -> Option<&'static ExprNode> {
+    match ExprNode::Butterflies {
+        ExprNode::ExprAddrOf => Some(&NODE),
+        _ => { let x = 5; None },
+    }
+}
+
+fn main() {}

diff --git a/tests/ui/single_match_else.stderr b/tests/ui/single_match_else.stderr
new file mode 100644 (file)
index 0000000..0b488b2
--- /dev/null
+++ b/tests/ui/single_match_else.stderr
@@ -0,0 +1,13 @@
+error: you seem to be trying to use match for destructuring a single pattern. Consider using `if let`
+  --> $DIR/single_match_else.rs:21:5
+   |
+21 | /     match ExprNode::Butterflies {
+22 | |         ExprNode::ExprAddrOf => Some(&NODE),
+23 | |         _ => { let x = 5; None },
+24 | |     }
+   | |_____^ help: try this: `if let ExprNode::ExprAddrOf = ExprNode::Butterflies { Some(&NODE) } else { let x = 5; None }`
+   |
+   = note: `-D clippy::single-match-else` implied by `-D warnings`
+
+error: aborting due to previous error
+