Try to solve issue3456. (rust-lang#3556)

src/expr.rs

@@ -1187,27 +1187,9 @@ fn rewrite_string_lit(context: &RewriteContext<'_>, span: Span, shape: Shape) ->
             .lines()
             .dropping_back(1)
             .all(|line| line.ends_with('\\'))
+            && context.config.version() == Version::Two
         {
-            let new_indent = shape.visual_indent(1).indent;
-            let indented_string_lit = String::from(
-                string_lit
-                    .lines()
-                    .map(|line| {
-                        format!(
-                            "{}{}",
-                            new_indent.to_string(context.config),
-                            line.trim_start()
-                        )
-                    })
-                    .collect::<Vec<_>>()
-                    .join("\n")
-                    .trim_start(),
-            );
-            return if context.config.version() == Version::Two {
-                Some(indented_string_lit)
-            } else {
-                wrap_str(indented_string_lit, context.config.max_width(), shape)
-            };
+            return Some(string_lit.to_owned());
         } else {
             return wrap_str(string_lit.to_owned(), context.config.max_width(), shape);
         }

src/utils.rs

@@ -618,9 +618,8 @@ pub(crate) fn trim_left_preserve_layout(
 
 /// Based on the given line, determine if the next line can be indented or not.
 /// This allows to preserve the indentation of multi-line literals.
-pub(crate) fn indent_next_line(kind: FullCodeCharKind, line: &str, config: &Config) -> bool {
+pub(crate) fn indent_next_line(kind: FullCodeCharKind, _line: &str, config: &Config) -> bool {
     !(kind.is_string() || (config.version() == Version::Two && kind.is_commented_string()))
-        || line.ends_with('\\')
 }
 
 pub(crate) fn is_empty_line(s: &str) -> bool {

tests/target/multiline_string_in_macro_def.rs

@@ -0,0 +1,14 @@
+macro_rules! assert_approx_eq {
+    ($a:expr, $b:expr, $eps:expr) => {{
+        let (a, b) = (&$a, &$b);
+        assert!(
+            (*a - *b).abs() < $eps,
+            "assertion failed: `(left !== right)` \
+             (left: `{:?}`, right: `{:?}`, expect diff: `{:?}`, real diff: `{:?}`)",
+            *a,
+            *b,
+            $eps,
+            (*a - *b).abs()
+        );
+    }};
+}

tests/target/should_not_format_string_when_format_strings_is_not_set.rs

@@ -0,0 +1,16 @@
+// format_strings is false by default.
+
+println!(
+    "DirEntry {{ \
+        binary_name: {:<64}, \
+        context_id: {:>2}, \
+        file_size: {:>6}, \
+        offset: 0x {:>08X}, \
+        actual_crc: 0x{:>08X} \
+    }}",
+    dir_entry.binary_name,
+    dir_entry.context_id,
+    dir_entry.file_size,
+    dir_entry.offset,
+    dir_entry.actual_crc
+);