Auto merge of rust-lang#10766 - samueltardieu:issue-10710, r=Manishearth

needless_bool: do not simplify code if it loses comments

Fix rust-lang#10710

changelog: [`needless_bool`]: do not simplify code if it loses comments

Author: bors

clippy_lints/src/needless_bool.rs

@@ -146,7 +146,7 @@ fn is_parent_stmt(cx: &LateContext<'_>, id: HirId) -> bool {
 impl<'tcx> LateLintPass<'tcx> for NeedlessBool {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
         use self::Expression::{Bool, RetBool};
-        if e.span.from_expansion() {
+        if e.span.from_expansion() || !span_extract_comment(cx.tcx.sess.source_map(), e.span).is_empty() {
             return;
         }
         if let Some(higher::If {
@@ -209,8 +209,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessBool {
             }
             if let Some((lhs_a, a)) = fetch_assign(then) &&
                 let Some((lhs_b, b)) = fetch_assign(r#else) &&
-                SpanlessEq::new(cx).eq_expr(lhs_a, lhs_b) &&
-                span_extract_comment(cx.tcx.sess.source_map(), e.span).is_empty()
+                SpanlessEq::new(cx).eq_expr(lhs_a, lhs_b)
             {
                 let mut applicability = Applicability::MachineApplicable;
                 let cond = Sugg::hir_with_applicability(cx, cond, "..", &mut applicability);

tests/ui/needless_bool/fixable.fixed

@@ -63,6 +63,13 @@ fn main() {
     needless_bool2(x);
     needless_bool3(x);
     needless_bool_condition();
+
+    if a == b {
+        true
+    } else {
+        // Do not lint as this comment might be important
+        false
+    };
 }
 
 fn bool_ret3(x: bool) -> bool {

tests/ui/needless_bool/fixable.rs

@@ -99,6 +99,13 @@ fn main() {
     needless_bool2(x);
     needless_bool3(x);
     needless_bool_condition();
+
+    if a == b {
+        true
+    } else {
+        // Do not lint as this comment might be important
+        false
+    };
 }
 
 fn bool_ret3(x: bool) -> bool {

tests/ui/needless_bool/fixable.stderr

@@ -91,7 +91,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `a < b`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:105:5
+  --> $DIR/fixable.rs:112:5
    |
 LL | /     if x {
 LL | |         return true;
@@ -101,7 +101,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:113:5
+  --> $DIR/fixable.rs:120:5
    |
 LL | /     if x {
 LL | |         return false;
@@ -111,7 +111,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return !x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:121:5
+  --> $DIR/fixable.rs:128:5
    |
 LL | /     if x && y {
 LL | |         return true;
@@ -121,7 +121,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return x && y`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:129:5
+  --> $DIR/fixable.rs:136:5
    |
 LL | /     if x && y {
 LL | |         return false;
@@ -131,33 +131,33 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return !(x && y)`
 
 error: equality checks against true are unnecessary
-  --> $DIR/fixable.rs:137:8
+  --> $DIR/fixable.rs:144:8
    |
 LL |     if x == true {};
    |        ^^^^^^^^^ help: try simplifying it as shown: `x`
    |
    = note: `-D clippy::bool-comparison` implied by `-D warnings`
 
 error: equality checks against false can be replaced by a negation
-  --> $DIR/fixable.rs:141:8
+  --> $DIR/fixable.rs:148:8
    |
 LL |     if x == false {};
    |        ^^^^^^^^^^ help: try simplifying it as shown: `!x`
 
 error: equality checks against true are unnecessary
-  --> $DIR/fixable.rs:151:8
+  --> $DIR/fixable.rs:158:8
    |
 LL |     if x == true {};
    |        ^^^^^^^^^ help: try simplifying it as shown: `x`
 
 error: equality checks against false can be replaced by a negation
-  --> $DIR/fixable.rs:152:8
+  --> $DIR/fixable.rs:159:8
    |
 LL |     if x == false {};
    |        ^^^^^^^^^^ help: try simplifying it as shown: `!x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:161:12
+  --> $DIR/fixable.rs:168:12
    |
 LL |       } else if returns_bool() {
    |  ____________^
@@ -168,7 +168,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `{ !returns_bool() }`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:174:5
+  --> $DIR/fixable.rs:181:5
    |
 LL | /     if unsafe { no(4) } & 1 != 0 {
 LL | |         true
@@ -178,13 +178,13 @@ LL | |     };
    | |_____^ help: you can reduce it to: `(unsafe { no(4) } & 1 != 0)`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:179:30
+  --> $DIR/fixable.rs:186:30
    |
 LL |     let _brackets_unneeded = if unsafe { no(4) } & 1 != 0 { true } else { false };
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `unsafe { no(4) } & 1 != 0`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:182:9
+  --> $DIR/fixable.rs:189:9
    |
 LL |         if unsafe { no(4) } & 1 != 0 { true } else { false }
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: you can reduce it to: `(unsafe { no(4) } & 1 != 0)`