Adjust rhs shape width to account for next line indentation

Fixes 5321

Previously the `Shape` returned from `expr::shape_from_rhs_tactic` would
always return a `Shape` with a `width` == `config.max_width` when the
`rhs_tactic` was `RhsTactics::ForceNextLineWithoutIndent` and the
indentation was 0. For example, when rewriting generic trait bounds at
the top level of a file.

In this case, trait bounds that were between (`max_width` - `tab_spaces`)
and `max_width`, would be considered properly formatted and wouldn't
wrap.

Now, the shape takes into account the whitespace to properly wrap
when the `max_width` is exceeded.

Author: ytmimi

src/expr.rs

@@ -2111,6 +2111,9 @@ fn shape_from_rhs_tactic(
     rhs_tactic: RhsTactics,
 ) -> Option<Shape> {
     match rhs_tactic {
+        RhsTactics::ForceNextLineWithoutIndent if shape.indent.width() == 0 => shape
+            .with_max_width(context.config)
+            .sub_width(context.config.tab_spaces()),
         RhsTactics::ForceNextLineWithoutIndent => shape
             .with_max_width(context.config)
             .sub_width(shape.indent.width()),

tests/source/issue_5321.rs

@@ -0,0 +1,17 @@
+trait AllTheOthers1: Trait3 + Trait4 + Trait5 + Trait6 + Trait7 + Trait8 + Trait9 + Trait10 + Trait11 + Trait12 + Trait14
+{
+}
+
+trait AllTheOthers2: Trait4 + Trait5 + Trait6 + Trait7 + Trait8 + Trait9 + Trait10 + Trait11 + Trait12 + Trait13 + Trait15
+{
+}
+
+mod Module {
+    trait AllTheOthers3: Trait5 + Trait6 + Trait7 + Trait8 + Trait9 + Trait10 + Trait11 + Trait12 + Trait13 + Trait14
+    {
+    }
+
+    trait AllTheOthers4: Trait6 + Trait7 + Trait8 + Trait9 + Trait10 + Trait11 + Trait12 + Trait13 + Trait14 + Trait15
+    {
+    }
+}

tests/target/issue_5321.rs

@@ -0,0 +1,50 @@
+trait AllTheOthers1:
+    Trait3
+    + Trait4
+    + Trait5
+    + Trait6
+    + Trait7
+    + Trait8
+    + Trait9
+    + Trait10
+    + Trait11
+    + Trait12
+    + Trait14
+{
+}
+
+trait AllTheOthers2:
+    Trait4
+    + Trait5
+    + Trait6
+    + Trait7
+    + Trait8
+    + Trait9
+    + Trait10
+    + Trait11
+    + Trait12
+    + Trait13
+    + Trait15
+{
+}
+
+mod Module {
+    trait AllTheOthers3:
+        Trait5 + Trait6 + Trait7 + Trait8 + Trait9 + Trait10 + Trait11 + Trait12 + Trait13 + Trait14
+    {
+    }
+
+    trait AllTheOthers4:
+        Trait6
+        + Trait7
+        + Trait8
+        + Trait9
+        + Trait10
+        + Trait11
+        + Trait12
+        + Trait13
+        + Trait14
+        + Trait15
+    {
+    }
+}