dedent better?

Author: ada4a

clippy_lints/src/duplicate_match_guards.rs

@@ -1,5 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::source::{HasSession, indent_of, reindent_multiline, snippet_with_applicability};
+use clippy_utils::source::{HasSession, indent_of, reindent_multiline, snippet_with_applicability, trim_span};
 use clippy_utils::{eq_expr_value, span_contains_comment};
 use rustc_errors::Applicability;
 use rustc_hir::{Arm, ExprKind};
@@ -119,27 +119,31 @@ impl<'tcx> LateLintPass<'tcx> for DuplicateMatchGuards {
                 then.span
             };
 
+            let sugg_span = trim_span(sm, sugg_span);
+
             let sugg = snippet_with_applicability(cx, sugg_span, "..", &mut applicability);
 
-            // we want to bring `then_without_curlies` to the level of indentation that
-            // `arm_body_expr` used to be at
-            //
+            // since we remove one level of curlies, we should be able to dedent `then` left one
+            // level, so this:
+            // ```
             // <pat> if <guard> => {
             //     if <cond> {
             //         then
             //         without
             //         curlies
             //     }
             // }
-            //
+            // ```
+            // becomes this:
+            // ```
             // <pat> if <guard> => {
             //     then
             //     without
             //     curlies
             // }
-            //
-            let indent = indent_of(cx, arm_body_expr.span);
-            let sugg = reindent_multiline(&sugg, false, indent);
+            // ```
+            let indent = indent_of(cx, sugg_span);
+            let sugg = reindent_multiline(&sugg, true, indent.map(|i| i.saturating_sub(4)));
 
             span_lint_and_sugg(
                 cx,

tests/ui/duplicate_match_guards.fixed

@@ -8,47 +8,39 @@ fn main() {
 
     match 0u32 {
         0 if true => {
-            
-                //~^ duplicate_match_guards
-                return;
-            
+            //~^ duplicate_match_guards
+            return;
         },
         0 if a > b => {
-            
-                //~^ duplicate_match_guards
-                return;
-            
+            //~^ duplicate_match_guards
+            return;
         },
         // not _identical_, but the meaning is the same
         0 if a > b => {
-            
-                //~^ duplicate_match_guards
-                return;
-            
+            //~^ duplicate_match_guards
+            return;
         },
         // a bit more complicated
         0 if a > 0 && b > 0 => {
-            
-                //~^ duplicate_match_guards
-                return;
-            
+            //~^ duplicate_match_guards
+            return;
         },
         // comments inside the inner block are preserved
         // (for comments _outside_ the inner block, see below)
         #[rustfmt::skip]
         0 if a > b => {
             //~ duplicate_match_guards
-/*before*/
-                return;
-                /* after
-            */
+        /*before*/
+                        return;
+                        /* after
+                    */
         },
         // no curlies around arm body
         #[rustfmt::skip] // would add the outer curlies
         0 if true => {
-                //~^ duplicate_match_guards
-                return;
-        },
+            //~^ duplicate_match_guards
+            return;
+    },
 
         // no warnings
         0 if true => {

tests/ui/duplicate_match_guards.stderr

@@ -11,10 +11,8 @@ LL | |             }
    = help: to override `-D warnings` add `#[allow(clippy::duplicate_match_guards)]`
 help: remove the condition
    |
-LL ~             
-LL +
-LL +                 return;
-LL +             
+LL ~
+LL +             return;
    |
 
 error: condition duplicates match guard
@@ -28,10 +26,8 @@ LL | |             }
    |
 help: remove the condition
    |
-LL ~             
-LL +
-LL +                 return;
-LL +             
+LL ~
+LL +             return;
    |
 
 error: condition duplicates match guard
@@ -45,10 +41,8 @@ LL | |             }
    |
 help: remove the condition
    |
-LL ~             
-LL +
-LL +                 return;
-LL +             
+LL ~
+LL +             return;
    |
 
 error: condition duplicates match guard
@@ -62,10 +56,8 @@ LL | |             }
    |
 help: remove the condition
    |
-LL ~             
-LL +
-LL +                 return;
-LL +             
+LL ~
+LL +             return;
    |
 
 error: condition duplicates match guard
@@ -81,10 +73,10 @@ LL | |             */}
 help: remove the condition
    |
 LL ~
-LL + /*before*/
-LL +                 return;
-LL +                 /* after
-LL +             */
+LL +         /*before*/
+LL +                         return;
+LL +                         /* after
+LL +                     */
    |
 
 error: condition duplicates match guard
@@ -101,8 +93,8 @@ help: remove the condition
    |
 LL ~         0 if true => {
 LL +
-LL +                 return;
-LL ~         },
+LL +             return;
+LL ~     },
    |
 
 error: aborting due to 6 previous errors