Don't skip semicolon if expressions follow

src/expr.rs

@@ -26,6 +26,7 @@ use crate::rewrite::{Rewrite, RewriteContext};
 use crate::shape::{Indent, Shape};
 use crate::source_map::{LineRangeUtils, SpanUtils};
 use crate::spanned::Spanned;
+use crate::stmt;
 use crate::string::{rewrite_string, StringFormat};
 use crate::types::{rewrite_path, PathContext};
 use crate::utils::{
@@ -515,9 +516,9 @@ fn rewrite_single_line_block(
     label: Option<ast::Label>,
     shape: Shape,
 ) -> Option<String> {
-    if is_simple_block(context, block, attrs) {
+    if let Some(block_expr) = stmt::Stmt::from_simple_block(context, block, attrs) {
         let expr_shape = shape.offset_left(last_line_width(prefix))?;
-        let expr_str = block.stmts[0].rewrite(context, expr_shape)?;
+        let expr_str = block_expr.rewrite(context, expr_shape)?;
         let label_str = rewrite_label(label);
         let result = format!("{}{}{{ {} }}", prefix, label_str, expr_str);
         if result.len() <= shape.width && !result.contains('\n') {
@@ -799,19 +800,19 @@ impl<'a> ControlFlow<'a> {
         let fixed_cost = self.keyword.len() + "  {  } else {  }".len();
 
         if let ast::ExprKind::Block(ref else_node, _) = else_block.kind {
-            if !is_simple_block(context, self.block, None)
-                || !is_simple_block(context, else_node, None)
-                || pat_expr_str.contains('\n')
-            {
-                return None;
-            }
+            let (if_expr, else_expr) = match (
+                stmt::Stmt::from_simple_block(context, self.block, None),
+                stmt::Stmt::from_simple_block(context, else_node, None),
+                pat_expr_str.contains('\n'),
+            ) {
+                (Some(if_expr), Some(else_expr), false) => (if_expr, else_expr),
+                _ => return None,
+            };
 
             let new_width = width.checked_sub(pat_expr_str.len() + fixed_cost)?;
-            let expr = &self.block.stmts[0];
-            let if_str = expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
+            let if_str = if_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 
             let new_width = new_width.checked_sub(if_str.len())?;
-            let else_expr = &else_node.stmts[0];
             let else_str = else_expr.rewrite(context, Shape::legacy(new_width, Indent::empty()))?;
 
             if if_str.contains('\n') || else_str.contains('\n') {

src/stmt.rs

@@ -3,7 +3,7 @@ use rustc_span::Span;
 
 use crate::comment::recover_comment_removed;
 use crate::config::Version;
-use crate::expr::{format_expr, ExprType};
+use crate::expr::{format_expr, is_simple_block, ExprType};
 use crate::rewrite::{Rewrite, RewriteContext};
 use crate::shape::Shape;
 use crate::source_map::LineRangeUtils;
@@ -33,6 +33,21 @@ impl<'a> Stmt<'a> {
         }
     }
 
+    pub(crate) fn from_simple_block(
+        context: &RewriteContext<'_>,
+        block: &'a ast::Block,
+        attrs: Option<&[ast::Attribute]>,
+    ) -> Option<Self> {
+        if is_simple_block(context, block, attrs) {
+            let inner = &block.stmts[0];
+            // Simple blocks only contain one expr and no stmts
+            let is_last = true;
+            Some(Stmt { inner, is_last })
+        } else {
+            None
+        }
+    }
+
     pub(crate) fn from_ast_node(inner: &'a ast::Stmt, is_last: bool) -> Self {
         Stmt { inner, is_last }
     }
@@ -80,13 +95,13 @@ impl<'a> Rewrite for Stmt<'a> {
         } else {
             ExprType::Statement
         };
-        format_stmt(context, shape, self.as_ast_node(), expr_type)
-    }
-}
-
-impl Rewrite for ast::Stmt {
-    fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
-        format_stmt(context, shape, self, ExprType::Statement)
+        format_stmt(
+            context,
+            shape,
+            self.as_ast_node(),
+            expr_type,
+            self.is_last_expr(),
+        )
     }
 }
 
@@ -95,13 +110,14 @@ fn format_stmt(
     shape: Shape,
     stmt: &ast::Stmt,
     expr_type: ExprType,
+    is_last_expr: bool,
 ) -> Option<String> {
     skip_out_of_file_lines_range!(context, stmt.span());
 
     let result = match stmt.kind {
         ast::StmtKind::Local(ref local) => local.rewrite(context, shape),
         ast::StmtKind::Expr(ref ex) | ast::StmtKind::Semi(ref ex) => {
-            let suffix = if semicolon_for_stmt(context, stmt) {
+            let suffix = if semicolon_for_stmt(context, stmt, is_last_expr) {
                 ";"
             } else {
                 ""

src/utils.rs

@@ -292,14 +292,20 @@ pub(crate) fn semicolon_for_expr(context: &RewriteContext<'_>, expr: &ast::Expr)
 }
 
 #[inline]
-pub(crate) fn semicolon_for_stmt(context: &RewriteContext<'_>, stmt: &ast::Stmt) -> bool {
+pub(crate) fn semicolon_for_stmt(
+    context: &RewriteContext<'_>,
+    stmt: &ast::Stmt,
+    is_last_expr: bool,
+) -> bool {
     match stmt.kind {
         ast::StmtKind::Semi(ref expr) => match expr.kind {
             ast::ExprKind::While(..) | ast::ExprKind::Loop(..) | ast::ExprKind::ForLoop(..) => {
                 false
             }
             ast::ExprKind::Break(..) | ast::ExprKind::Continue(..) | ast::ExprKind::Ret(..) => {
-                context.config.trailing_semicolon()
+                // The only time we can skip the semi-colon is if the config option is set to false
+                // **and** this is the last expr (even though any following exprs are unreachable)
+                context.config.trailing_semicolon() || !is_last_expr
             }
             _ => true,
         },

tests/target/issue-5797/retain_trailing_semicolon.rs

@@ -0,0 +1,7 @@
+// rustfmt-trailing_semicolon: false
+
+fn foo() {}
+fn main() {
+    return;
+    foo()
+}