Fix up formatting bugs in impl and trait

src/items.rs

@@ -33,8 +33,8 @@ use types::join_bounds;
 use utils::{colon_spaces, contains_skip, first_line_width, format_abi, format_constness,
             format_defaultness, format_mutability, format_unsafety, format_visibility,
             is_attributes_extendable, last_line_contains_single_line_comment,
-            last_line_used_width, last_line_width, mk_sp, semicolon_for_expr, starts_with_newline,
-            stmt_expr, trimmed_last_line_width};
+            last_line_extendable, last_line_used_width, last_line_width, mk_sp,
+            semicolon_for_expr, starts_with_newline, stmt_expr, trimmed_last_line_width};
 use vertical::rewrite_with_alignment;
 use visitor::FmtVisitor;
 
@@ -639,8 +639,10 @@ pub fn format_impl(
         }
         result.push_str(&where_clause_str);
 
+        let need_newline = !last_line_extendable(&result)
+            && (last_line_contains_single_line_comment(&result) || result.contains('\n'));
         match context.config.brace_style() {
-            _ if last_line_contains_single_line_comment(&result) => result.push_str(&sep),
+            _ if need_newline => result.push_str(&sep),
             BraceStyle::AlwaysNextLine => result.push_str(&sep),
             BraceStyle::PreferSameLine => result.push(' '),
             BraceStyle::SameLineWhere => {
@@ -938,7 +940,7 @@ pub fn format_trait(context: &RewriteContext, item: &ast::Item, offset: Indent)
 
         let body_lo = context.codemap.span_after(item.span, "{");
 
-        let shape = Shape::indented(offset, context.config);
+        let shape = Shape::indented(offset, context.config).offset_left(result.len())?;
         let generics_str =
             rewrite_generics(context, generics, shape, mk_sp(item.span.lo(), body_lo))?;
         result.push_str(&generics_str);

src/utils.rs

@@ -178,7 +178,7 @@ pub fn last_line_extendable(s: &str) -> bool {
     }
     for c in s.chars().rev() {
         match c {
-            ')' | ']' | '}' | '?' => continue,
+            ')' | ']' | '}' | '?' | '>' => continue,
             '\n' => break,
             _ if c.is_whitespace() => continue,
             _ => return false,

tests/source/trait.rs

@@ -72,6 +72,11 @@ trait Foo {
     type IteRev = <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
 }
 
+// #2331
+trait MyTrait<AAAAAAAAAAAAAAAAAAAA, BBBBBBBBBBBBBBBBBBBB, CCCCCCCCCCCCCCCCCCCC, DDDDDDDDDDDDDDDDDDDD> {
+    fn foo() {}
+}
+
 // Trait aliases
 trait FooBar =
     Foo 

tests/target/big-impl-rfc.rs

@@ -29,19 +29,22 @@ where
 
 // #1369
 impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl<
     ExcessivelyLongGenericName,
     ExcessivelyLongGenericName,
     AnotherExcessivelyLongGenericName,
 > Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo

tests/target/big-impl.rs

@@ -27,19 +27,22 @@ where
 
 // #1369
 impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl<
     ExcessivelyLongGenericName,
     ExcessivelyLongGenericName,
     AnotherExcessivelyLongGenericName,
 > Foo<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName>
-    for Bar {
+    for Bar
+{
     fn foo() {}
 }
 impl<ExcessivelyLongGenericName, ExcessivelyLongGenericName, AnotherExcessivelyLongGenericName> Foo

tests/target/impls.rs

@@ -141,11 +141,13 @@ mod m {
 }
 
 impl<BorrowType, K, V, NodeType, HandleType>
-    Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType> {
+    Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
+{
 }
 
 impl<BorrowType, K, V, NodeType, HandleType> PartialEq
-    for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType> {
+    for Handle<NodeRef<BorrowType, K, V, NodeType>, HandleType>
+{
 }
 
 mod x {
@@ -160,7 +162,8 @@ mod x {
 }
 
 impl<ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNodeFoo>
-    Issue1249<ConcreteThreadSafeLayoutNode> {
+    Issue1249<ConcreteThreadSafeLayoutNode>
+{
     // Creates a new flow constructor.
     fn foo() {}
 }

tests/target/trait.rs

@@ -100,6 +100,16 @@ trait Foo {
         <MergingUntypedTimeSeries<SliceSeries<SliceWindow>> as UntypedTimeSeries>::IterRev;
 }
 
+// #2331
+trait MyTrait<
+    AAAAAAAAAAAAAAAAAAAA,
+    BBBBBBBBBBBBBBBBBBBB,
+    CCCCCCCCCCCCCCCCCCCC,
+    DDDDDDDDDDDDDDDDDDDD,
+> {
+    fn foo() {}
+}
+
 // Trait aliases
 trait FooBar = Foo + Bar;
 trait FooBar<A, B, C> = Foo + Bar;