enhance const block formatting

Author: frbimo

src/formatting/expr.rs

@@ -125,7 +125,29 @@ pub(crate) fn format_expr(
         | ast::ExprKind::While(..) => to_control_flow(expr, expr_type)
             .and_then(|control_flow| control_flow.rewrite(context, shape)),
         ast::ExprKind::ConstBlock(ref anon_const) => {
-            Some(format!("const {}", anon_const.rewrite(context, shape)?))
+            let between_span = mk_sp(
+                context.snippet_provider.span_after(expr.span, "const"),
+                anon_const.value.span.lo(),
+            );
+            let mut result = "const".to_string();
+            let post_comment = rewrite_missing_comment(between_span, shape, context)?;
+            if contains_comment(context.snippet(between_span)) {
+                result.push_str(" ");
+                result.push_str(&post_comment);
+            }
+            match context.config.brace_style() {
+                BraceStyle::AlwaysNextLine => Some(format!(
+                    "{}{}{}",
+                    result,
+                    shape.to_string_with_newline(context.config),
+                    anon_const.rewrite(context, shape)?
+                )),
+                _ => Some(format!(
+                    "{} {}",
+                    result,
+                    anon_const.rewrite(context, shape)?
+                )),
+            }
         }
         ast::ExprKind::Block(ref block, opt_label) => {
             match expr_type {

tests/source/configs/brace_style/const_block_always_next_line.rs

@@ -0,0 +1,45 @@
+// rustfmt-brace_style: AlwaysNextLine
+// AlwaysNextLine brace style for const blocks
+
+fn foo() -> i32 {
+    const {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn bar() -> i32 {
+    const { 4 }
+}
+
+fn foo() -> i32 {
+    const
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */ {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const
+/*qux */
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}

tests/source/configs/brace_style/const_block_same_line_where.rs

@@ -0,0 +1,45 @@
+// rustfmt-brace_style: SameLineWhere
+// SameLineWhere brace style for const blocks
+
+fn foo() -> i32 {
+    const {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn bar() -> i32 {
+    const { 4 }
+}
+
+fn foo() -> i32 {
+    const
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */ {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const
+/*qux */
+{
+        let x = 5 + 10;
+        x / 3
+    }
+}

tests/target/configs/brace_style/const_block_always_next_line.rs

@@ -0,0 +1,53 @@
+// rustfmt-brace_style: AlwaysNextLine
+// AlwaysNextLine brace style for const blocks
+
+fn foo() -> i32
+{
+    const
+    {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn bar() -> i32
+{
+    const
+    { 4 }
+}
+
+fn foo() -> i32
+{
+    const
+    {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32
+{
+    const /*qux */
+    {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32
+{
+    const /*qux */
+    {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32
+{
+    const /*qux */
+    {
+        let x = 5 + 10;
+        x / 3
+    }
+}

tests/target/configs/brace_style/const_block_same_line_where.rs

@@ -0,0 +1,41 @@
+// rustfmt-brace_style: SameLineWhere
+// SameLineWhere brace style for const blocks
+
+fn foo() -> i32 {
+    const {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn bar() -> i32 {
+    const { 4 }
+}
+
+fn foo() -> i32 {
+    const {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */ {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */ {
+        let x = 5 + 10;
+        x / 3
+    }
+}
+
+fn foo() -> i32 {
+    const /*qux */ {
+        let x = 5 + 10;
+        x / 3
+    }
+}