Rollup merge of rust-lang#5752 - chrisduerr:pedantic_ranges, r=flip1995

Move range_minus_one to pedantic

This moves the range_minus_one lint to the pedantic category, so there
will not be any warnings emitted by default. This should work around
problems where the suggestion is impossible to resolve due to the range
consumer only accepting a specific range implementation, rather than the
`RangeBounds` trait (see rust-lang#3307).

While it is possible to work around this by extracting the boundary into
a variable, I don't think clippy should encourage people to disable or
work around lints, but instead the lints should be fixable. So hopefully
this will help until a proper implementation checks what the range is
used for.

*Please keep the line below*
changelog: move [`range_minus_one`] to pedantic

Author: flip1995

clippy_lints/src/lib.rs

@@ -1161,6 +1161,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&needless_pass_by_value::NEEDLESS_PASS_BY_VALUE),
         LintId::of(&non_expressive_names::SIMILAR_NAMES),
         LintId::of(&option_if_let_else::OPTION_IF_LET_ELSE),
+        LintId::of(&ranges::RANGE_MINUS_ONE),
         LintId::of(&ranges::RANGE_PLUS_ONE),
         LintId::of(&shadow::SHADOW_UNRELATED),
         LintId::of(&strings::STRING_ADD_ASSIGN),
@@ -1383,7 +1384,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&ptr::PTR_ARG),
         LintId::of(&ptr_offset_with_cast::PTR_OFFSET_WITH_CAST),
         LintId::of(&question_mark::QUESTION_MARK),
-        LintId::of(&ranges::RANGE_MINUS_ONE),
         LintId::of(&ranges::RANGE_ZIP_WITH_LEN),
         LintId::of(&ranges::REVERSED_EMPTY_RANGES),
         LintId::of(&redundant_clone::REDUNDANT_CLONE),
@@ -1599,7 +1599,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&partialeq_ne_impl::PARTIALEQ_NE_IMPL),
         LintId::of(&precedence::PRECEDENCE),
         LintId::of(&ptr_offset_with_cast::PTR_OFFSET_WITH_CAST),
-        LintId::of(&ranges::RANGE_MINUS_ONE),
         LintId::of(&ranges::RANGE_ZIP_WITH_LEN),
         LintId::of(&reference::DEREF_ADDROF),
         LintId::of(&reference::REF_IN_DEREF),

clippy_lints/src/ranges.rs

@@ -52,6 +52,11 @@ declare_clippy_lint! {
     /// exclusive ranges, because they essentially add an extra branch that
     /// LLVM may fail to hoist out of the loop.
     ///
+    /// This will cause a warning that cannot be fixed if the consumer of the
+    /// range only accepts a specific range type, instead of the generic
+    /// `RangeBounds` trait
+    /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
+    ///
     /// **Example:**
     /// ```rust,ignore
     /// for x..(y+1) { .. }
@@ -72,7 +77,10 @@ declare_clippy_lint! {
     /// **Why is this bad?** The code is more readable with an exclusive range
     /// like `x..y`.
     ///
-    /// **Known problems:** None.
+    /// **Known problems:** This will cause a warning that cannot be fixed if
+    /// the consumer of the range only accepts a specific range type, instead of
+    /// the generic `RangeBounds` trait
+    /// ([#3307](https://github.com/rust-lang/rust-clippy/issues/3307)).
     ///
     /// **Example:**
     /// ```rust,ignore
@@ -83,7 +91,7 @@ declare_clippy_lint! {
     /// for x..y { .. }
     /// ```
     pub RANGE_MINUS_ONE,
-    complexity,
+    pedantic,
     "`x..=(y-1)` reads better as `x..y`"
 }
 

src/lintlist/mod.rs

@@ -1790,7 +1790,7 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
     },
     Lint {
         name: "range_minus_one",
-        group: "complexity",
+        group: "pedantic",
         desc: "`x..=(y-1)` reads better as `x..y`",
         deprecation: None,
         module: "ranges",

tests/ui/range_plus_minus_one.fixed

@@ -7,6 +7,7 @@ fn f() -> usize {
 }
 
 #[warn(clippy::range_plus_one)]
+#[warn(clippy::range_minus_one)]
 fn main() {
     for _ in 0..2 {}
     for _ in 0..=2 {}

tests/ui/range_plus_minus_one.rs

@@ -7,6 +7,7 @@ fn f() -> usize {
 }
 
 #[warn(clippy::range_plus_one)]
+#[warn(clippy::range_minus_one)]
 fn main() {
     for _ in 0..2 {}
     for _ in 0..=2 {}

tests/ui/range_plus_minus_one.stderr

@@ -1,57 +1,57 @@
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:14:14
+  --> $DIR/range_plus_minus_one.rs:15:14
    |
 LL |     for _ in 0..3 + 1 {}
    |              ^^^^^^^^ help: use: `0..=3`
    |
    = note: `-D clippy::range-plus-one` implied by `-D warnings`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:17:14
+  --> $DIR/range_plus_minus_one.rs:18:14
    |
 LL |     for _ in 0..1 + 5 {}
    |              ^^^^^^^^ help: use: `0..=5`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:20:14
+  --> $DIR/range_plus_minus_one.rs:21:14
    |
 LL |     for _ in 1..1 + 1 {}
    |              ^^^^^^^^ help: use: `1..=1`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:26:14
+  --> $DIR/range_plus_minus_one.rs:27:14
    |
 LL |     for _ in 0..(1 + f()) {}
    |              ^^^^^^^^^^^^ help: use: `0..=f()`
 
 error: an exclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:30:13
+  --> $DIR/range_plus_minus_one.rs:31:13
    |
 LL |     let _ = ..=11 - 1;
    |             ^^^^^^^^^ help: use: `..11`
    |
    = note: `-D clippy::range-minus-one` implied by `-D warnings`
 
 error: an exclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:31:13
+  --> $DIR/range_plus_minus_one.rs:32:13
    |
 LL |     let _ = ..=(11 - 1);
    |             ^^^^^^^^^^^ help: use: `..11`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:32:13
+  --> $DIR/range_plus_minus_one.rs:33:13
    |
 LL |     let _ = (1..11 + 1);
    |             ^^^^^^^^^^^ help: use: `(1..=11)`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:33:13
+  --> $DIR/range_plus_minus_one.rs:34:13
    |
 LL |     let _ = (f() + 1)..(f() + 1);
    |             ^^^^^^^^^^^^^^^^^^^^ help: use: `((f() + 1)..=f())`
 
 error: an inclusive range would be more readable
-  --> $DIR/range_plus_minus_one.rs:37:14
+  --> $DIR/range_plus_minus_one.rs:38:14
    |
 LL |     for _ in 1..ONE + ONE {}
    |              ^^^^^^^^^^^^ help: use: `1..=ONE`