Fix/Inconsistent Struct Body Opening Brace Placement After Where Clause

src/items.rs

@@ -1262,6 +1262,34 @@ fn format_unit_struct(
     Some(format!("{}{};", header_str, generics_str))
 }
 
+fn set_brace_pos(
+    context: &RewriteContext<'_>,
+    struct_parts: &StructParts<'_>,
+    fields: &[ast::FieldDef],
+    body_lo: BytePos,
+) -> BracePos {
+    if fields.is_empty() {
+        let span = struct_parts.span;
+        let generics_lo = if let Some(generics) = struct_parts.generics {
+            generics.span.lo()
+        } else {
+            body_lo
+        };
+        let snippet = context.snippet(mk_sp(generics_lo, span.hi()));
+        let body_contains_comments = contains_comment(snippet);
+        if context.config.version() == Version::Two {
+            return match (fields.is_empty(), body_contains_comments) {
+                (true, true) => BracePos::Auto,
+                (true, false) if struct_parts.generics.is_some() => BracePos::Auto,
+                (true, false) => BracePos::ForceSameLine,
+                (false, _) => BracePos::Auto,
+            };
+        }
+        return BracePos::ForceSameLine;
+    }
+    BracePos::Auto
+}
+
 pub(crate) fn format_struct_struct(
     context: &RewriteContext<'_>,
     struct_parts: &StructParts<'_>,
@@ -1289,11 +1317,7 @@ pub(crate) fn format_struct_struct(
             context,
             g,
             context.config.brace_style(),
-            if fields.is_empty() {
-                BracePos::ForceSameLine
-            } else {
-                BracePos::Auto
-            },
+            set_brace_pos(&context, &struct_parts, &fields, body_lo),
             offset,
             // make a span that starts right after `struct Foo`
             mk_sp(header_hi, body_lo),

tests/source/issue-5507/issue-5507-version-one.rs

@@ -0,0 +1,28 @@
+// rustfmt-version: One
+
+struct EmptyBody<T>
+    where T: Eq {
+}
+
+struct LineComment<T>
+    where T: Eq {
+    // body
+}
+
+struct MultiLineComment<T>
+    where T: Eq {
+    /*
+    Multiline
+    comment.
+    */
+}
+
+struct BlockComment<T>
+    where T: Eq {
+    /* block comment */
+}
+
+struct HasBody<T>
+    where T: Eq {
+    x: T
+}

tests/source/issue-5507/issue-5507-version-two.rs

@@ -0,0 +1,28 @@
+// rustfmt-version: Two
+
+struct EmptyBody<T>
+    where T: Eq {
+}
+
+struct LineComment<T>
+    where T: Eq {
+    // body
+}
+
+struct MultiLineComment<T>
+    where T: Eq {
+    /*
+    Multiline
+    comment.
+    */
+}
+
+struct BlockComment<T>
+    where T: Eq {
+    /* block comment */
+}
+
+struct HasBody<T>
+    where T: Eq {
+    x: T
+}

tests/target/issue-5507/issue-5507-version-one.rs

@@ -0,0 +1,31 @@
+// rustfmt-version: One
+
+struct EmptyBody<T>
+where
+    T: Eq, {}
+
+struct LineComment<T>
+where
+    T: Eq, {
+    // body
+}
+
+struct MultiLineComment<T>
+where
+    T: Eq, {
+    /*
+    Multiline
+    comment.
+    */
+}
+
+struct BlockComment<T>
+where
+    T: Eq, {/* block comment */}
+
+struct HasBody<T>
+where
+    T: Eq,
+{
+    x: T,
+}

tests/target/issue-5507/issue-5507-version-two.rs

@@ -0,0 +1,35 @@
+// rustfmt-version: Two
+
+struct EmptyBody<T>
+where
+    T: Eq,
+{}
+
+struct LineComment<T>
+where
+    T: Eq,
+{
+    // body
+}
+
+struct MultiLineComment<T>
+where
+    T: Eq,
+{
+    /*
+    Multiline
+    comment.
+    */
+}
+
+struct BlockComment<T>
+where
+    T: Eq,
+{/* block comment */}
+
+struct HasBody<T>
+where
+    T: Eq,
+{
+    x: T,
+}