1 files changed, 373 insertions, 0 deletions
diff --git a/src/tools/rustfmt/src/shape.rs b/src/tools/rustfmt/src/shape.rs
new file mode 100644
index 000000000..4376fd12b
--- /dev/null
+++ b/src/tools/rustfmt/src/shape.rs
@@ -0,0 +1,373 @@
+use std::borrow::Cow;
+use std::cmp::min;
+use std::ops::{Add, Sub};
+
+use crate::Config;
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct Indent {
+    // Width of the block indent, in characters. Must be a multiple of
+    // Config::tab_spaces.
+    pub(crate) block_indent: usize,
+    // Alignment in characters.
+    pub(crate) alignment: usize,
+}
+
+// INDENT_BUFFER.len() = 81
+const INDENT_BUFFER_LEN: usize = 80;
+const INDENT_BUFFER: &str =
+    "\n                                                                                ";
+
+impl Indent {
+    pub(crate) fn new(block_indent: usize, alignment: usize) -> Indent {
+        Indent {
+            block_indent,
+            alignment,
+        }
+    }
+
+    pub(crate) fn from_width(config: &Config, width: usize) -> Indent {
+        if config.hard_tabs() {
+            let tab_num = width / config.tab_spaces();
+            let alignment = width % config.tab_spaces();
+            Indent::new(config.tab_spaces() * tab_num, alignment)
+        } else {
+            Indent::new(width, 0)
+        }
+    }
+
+    pub(crate) fn empty() -> Indent {
+        Indent::new(0, 0)
+    }
+
+    pub(crate) fn block_only(&self) -> Indent {
+        Indent {
+            block_indent: self.block_indent,
+            alignment: 0,
+        }
+    }
+
+    pub(crate) fn block_indent(mut self, config: &Config) -> Indent {
+        self.block_indent += config.tab_spaces();
+        self
+    }
+
+    pub(crate) fn block_unindent(mut self, config: &Config) -> Indent {
+        if self.block_indent < config.tab_spaces() {
+            Indent::new(self.block_indent, 0)
+        } else {
+            self.block_indent -= config.tab_spaces();
+            self
+        }
+    }
+
+    pub(crate) fn width(&self) -> usize {
+        self.block_indent + self.alignment
+    }
+
+    pub(crate) fn to_string(&self, config: &Config) -> Cow<'static, str> {
+        self.to_string_inner(config, 1)
+    }
+
+    pub(crate) fn to_string_with_newline(&self, config: &Config) -> Cow<'static, str> {
+        self.to_string_inner(config, 0)
+    }
+
+    fn to_string_inner(&self, config: &Config, offset: usize) -> Cow<'static, str> {
+        let (num_tabs, num_spaces) = if config.hard_tabs() {
+            (self.block_indent / config.tab_spaces(), self.alignment)
+        } else {
+            (0, self.width())
+        };
+        let num_chars = num_tabs + num_spaces;
+        if num_tabs == 0 && num_chars + offset <= INDENT_BUFFER_LEN {
+            Cow::from(&INDENT_BUFFER[offset..=num_chars])
+        } else {
+            let mut indent = String::with_capacity(num_chars + if offset == 0 { 1 } else { 0 });
+            if offset == 0 {
+                indent.push('\n');
+            }
+            for _ in 0..num_tabs {
+                indent.push('\t')
+            }
+            for _ in 0..num_spaces {
+                indent.push(' ')
+            }
+            Cow::from(indent)
+        }
+    }
+}
+
+impl Add for Indent {
+    type Output = Indent;
+
+    fn add(self, rhs: Indent) -> Indent {
+        Indent {
+            block_indent: self.block_indent + rhs.block_indent,
+            alignment: self.alignment + rhs.alignment,
+        }
+    }
+}
+
+impl Sub for Indent {
+    type Output = Indent;
+
+    fn sub(self, rhs: Indent) -> Indent {
+        Indent::new(
+            self.block_indent - rhs.block_indent,
+            self.alignment - rhs.alignment,
+        )
+    }
+}
+
+impl Add<usize> for Indent {
+    type Output = Indent;
+
+    fn add(self, rhs: usize) -> Indent {
+        Indent::new(self.block_indent, self.alignment + rhs)
+    }
+}
+
+impl Sub<usize> for Indent {
+    type Output = Indent;
+
+    fn sub(self, rhs: usize) -> Indent {
+        Indent::new(self.block_indent, self.alignment - rhs)
+    }
+}
+
+// 8096 is close enough to infinite for rustfmt.
+const INFINITE_SHAPE_WIDTH: usize = 8096;
+
+#[derive(Copy, Clone, Debug)]
+pub(crate) struct Shape {
+    pub(crate) width: usize,
+    // The current indentation of code.
+    pub(crate) indent: Indent,
+    // Indentation + any already emitted text on the first line of the current
+    // statement.
+    pub(crate) offset: usize,
+}
+
+impl Shape {
+    /// `indent` is the indentation of the first line. The next lines
+    /// should begin with at least `indent` spaces (except backwards
+    /// indentation). The first line should not begin with indentation.
+    /// `width` is the maximum number of characters on the last line
+    /// (excluding `indent`). The width of other lines is not limited by
+    /// `width`.
+    /// Note that in reality, we sometimes use width for lines other than the
+    /// last (i.e., we are conservative).
+    // .......*-------*
+    //        |       |
+    //        |     *-*
+    //        *-----|
+    // |<------------>|  max width
+    // |<---->|          indent
+    //        |<--->|    width
+    pub(crate) fn legacy(width: usize, indent: Indent) -> Shape {
+        Shape {
+            width,
+            indent,
+            offset: indent.alignment,
+        }
+    }
+
+    pub(crate) fn indented(indent: Indent, config: &Config) -> Shape {
+        Shape {
+            width: config.max_width().saturating_sub(indent.width()),
+            indent,
+            offset: indent.alignment,
+        }
+    }
+
+    pub(crate) fn with_max_width(&self, config: &Config) -> Shape {
+        Shape {
+            width: config.max_width().saturating_sub(self.indent.width()),
+            ..*self
+        }
+    }
+
+    pub(crate) fn visual_indent(&self, extra_width: usize) -> Shape {
+        let alignment = self.offset + extra_width;
+        Shape {
+            width: self.width,
+            indent: Indent::new(self.indent.block_indent, alignment),
+            offset: alignment,
+        }
+    }
+
+    pub(crate) fn block_indent(&self, extra_width: usize) -> Shape {
+        if self.indent.alignment == 0 {
+            Shape {
+                width: self.width,
+                indent: Indent::new(self.indent.block_indent + extra_width, 0),
+                offset: 0,
+            }
+        } else {
+            Shape {
+                width: self.width,
+                indent: self.indent + extra_width,
+                offset: self.indent.alignment + extra_width,
+            }
+        }
+    }
+
+    pub(crate) fn block_left(&self, width: usize) -> Option<Shape> {
+        self.block_indent(width).sub_width(width)
+    }
+
+    pub(crate) fn add_offset(&self, extra_width: usize) -> Shape {
+        Shape {
+            offset: self.offset + extra_width,
+            ..*self
+        }
+    }
+
+    pub(crate) fn block(&self) -> Shape {
+        Shape {
+            indent: self.indent.block_only(),
+            ..*self
+        }
+    }
+
+    pub(crate) fn saturating_sub_width(&self, width: usize) -> Shape {
+        self.sub_width(width).unwrap_or(Shape { width: 0, ..*self })
+    }
+
+    pub(crate) fn sub_width(&self, width: usize) -> Option<Shape> {
+        Some(Shape {
+            width: self.width.checked_sub(width)?,
+            ..*self
+        })
+    }
+
+    pub(crate) fn shrink_left(&self, width: usize) -> Option<Shape> {
+        Some(Shape {
+            width: self.width.checked_sub(width)?,
+            indent: self.indent + width,
+            offset: self.offset + width,
+        })
+    }
+
+    pub(crate) fn offset_left(&self, width: usize) -> Option<Shape> {
+        self.add_offset(width).sub_width(width)
+    }
+
+    pub(crate) fn used_width(&self) -> usize {
+        self.indent.block_indent + self.offset
+    }
+
+    pub(crate) fn rhs_overhead(&self, config: &Config) -> usize {
+        config
+            .max_width()
+            .saturating_sub(self.used_width() + self.width)
+    }
+
+    pub(crate) fn comment(&self, config: &Config) -> Shape {
+        let width = min(
+            self.width,
+            config.comment_width().saturating_sub(self.indent.width()),
+        );
+        Shape { width, ..*self }
+    }
+
+    pub(crate) fn to_string_with_newline(&self, config: &Config) -> Cow<'static, str> {
+        let mut offset_indent = self.indent;
+        offset_indent.alignment = self.offset;
+        offset_indent.to_string_inner(config, 0)
+    }
+
+    /// Creates a `Shape` with a virtually infinite width.
+    pub(crate) fn infinite_width(&self) -> Shape {
+        Shape {
+            width: INFINITE_SHAPE_WIDTH,
+            ..*self
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn indent_add_sub() {
+        let indent = Indent::new(4, 8) + Indent::new(8, 12);
+        assert_eq!(12, indent.block_indent);
+        assert_eq!(20, indent.alignment);
+
+        let indent = indent - Indent::new(4, 4);
+        assert_eq!(8, indent.block_indent);
+        assert_eq!(16, indent.alignment);
+    }
+
+    #[test]
+    fn indent_add_sub_alignment() {
+        let indent = Indent::new(4, 8) + 4;
+        assert_eq!(4, indent.block_indent);
+        assert_eq!(12, indent.alignment);
+
+        let indent = indent - 4;
+        assert_eq!(4, indent.block_indent);
+        assert_eq!(8, indent.alignment);
+    }
+
+    #[test]
+    fn indent_to_string_spaces() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+
+        // 12 spaces
+        assert_eq!("            ", indent.to_string(&config));
+    }
+
+    #[test]
+    fn indent_to_string_hard_tabs() {
+        let mut config = Config::default();
+        config.set().hard_tabs(true);
+        let indent = Indent::new(8, 4);
+
+        // 2 tabs + 4 spaces
+        assert_eq!("\t\t    ", indent.to_string(&config));
+    }
+
+    #[test]
+    fn shape_visual_indent() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.visual_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(4, shape.indent.block_indent);
+        assert_eq!(28, shape.indent.alignment);
+        assert_eq!(28, shape.offset);
+    }
+
+    #[test]
+    fn shape_block_indent_without_alignment() {
+        let config = Config::default();
+        let indent = Indent::new(4, 0);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.block_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(24, shape.indent.block_indent);
+        assert_eq!(0, shape.indent.alignment);
+        assert_eq!(0, shape.offset);
+    }
+
+    #[test]
+    fn shape_block_indent_with_alignment() {
+        let config = Config::default();
+        let indent = Indent::new(4, 8);
+        let shape = Shape::legacy(config.max_width(), indent);
+        let shape = shape.block_indent(20);
+
+        assert_eq!(config.max_width(), shape.width);
+        assert_eq!(4, shape.indent.block_indent);
+        assert_eq!(28, shape.indent.alignment);
+        assert_eq!(28, shape.offset);
+    }
+}