1 files changed, 179 insertions, 0 deletions
diff --git a/compiler/rustc_errors/src/snippet.rs b/compiler/rustc_errors/src/snippet.rs
new file mode 100644
index 000000000..e4cc44c41
--- /dev/null
+++ b/compiler/rustc_errors/src/snippet.rs
@@ -0,0 +1,179 @@
+// Code for annotating snippets.
+
+use crate::Level;
+
+#[derive(Clone, Debug, PartialOrd, Ord, PartialEq, Eq)]
+pub struct Line {
+    pub line_index: usize,
+    pub annotations: Vec<Annotation>,
+}
+
+#[derive(Clone, Debug, PartialOrd, Ord, PartialEq, Eq)]
+pub struct MultilineAnnotation {
+    pub depth: usize,
+    pub line_start: usize,
+    pub line_end: usize,
+    pub start_col: usize,
+    pub end_col: usize,
+    pub is_primary: bool,
+    pub label: Option<String>,
+    pub overlaps_exactly: bool,
+}
+
+impl MultilineAnnotation {
+    pub fn increase_depth(&mut self) {
+        self.depth += 1;
+    }
+
+    /// Compare two `MultilineAnnotation`s considering only the `Span` they cover.
+    pub fn same_span(&self, other: &MultilineAnnotation) -> bool {
+        self.line_start == other.line_start
+            && self.line_end == other.line_end
+            && self.start_col == other.start_col
+            && self.end_col == other.end_col
+    }
+
+    pub fn as_start(&self) -> Annotation {
+        Annotation {
+            start_col: self.start_col,
+            end_col: self.start_col + 1,
+            is_primary: self.is_primary,
+            label: None,
+            annotation_type: AnnotationType::MultilineStart(self.depth),
+        }
+    }
+
+    pub fn as_end(&self) -> Annotation {
+        Annotation {
+            start_col: self.end_col.saturating_sub(1),
+            end_col: self.end_col,
+            is_primary: self.is_primary,
+            label: self.label.clone(),
+            annotation_type: AnnotationType::MultilineEnd(self.depth),
+        }
+    }
+
+    pub fn as_line(&self) -> Annotation {
+        Annotation {
+            start_col: 0,
+            end_col: 0,
+            is_primary: self.is_primary,
+            label: None,
+            annotation_type: AnnotationType::MultilineLine(self.depth),
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialOrd, Ord, PartialEq, Eq)]
+pub enum AnnotationType {
+    /// Annotation under a single line of code
+    Singleline,
+
+    // The Multiline type above is replaced with the following three in order
+    // to reuse the current label drawing code.
+    //
+    // Each of these corresponds to one part of the following diagram:
+    //
+    //     x |   foo(1 + bar(x,
+    //       |  _________^              < MultilineStart
+    //     x | |             y),        < MultilineLine
+    //       | |______________^ label   < MultilineEnd
+    //     x |       z);
+    /// Annotation marking the first character of a fully shown multiline span
+    MultilineStart(usize),
+    /// Annotation marking the last character of a fully shown multiline span
+    MultilineEnd(usize),
+    /// Line at the left enclosing the lines of a fully shown multiline span
+    // Just a placeholder for the drawing algorithm, to know that it shouldn't skip the first 4
+    // and last 2 lines of code. The actual line is drawn in `emit_message_default` and not in
+    // `draw_multiline_line`.
+    MultilineLine(usize),
+}
+
+#[derive(Clone, Debug, PartialOrd, Ord, PartialEq, Eq)]
+pub struct Annotation {
+    /// Start column, 0-based indexing -- counting *characters*, not
+    /// utf-8 bytes. Note that it is important that this field goes
+    /// first, so that when we sort, we sort orderings by start
+    /// column.
+    pub start_col: usize,
+
+    /// End column within the line (exclusive)
+    pub end_col: usize,
+
+    /// Is this annotation derived from primary span
+    pub is_primary: bool,
+
+    /// Optional label to display adjacent to the annotation.
+    pub label: Option<String>,
+
+    /// Is this a single line, multiline or multiline span minimized down to a
+    /// smaller span.
+    pub annotation_type: AnnotationType,
+}
+
+impl Annotation {
+    /// Whether this annotation is a vertical line placeholder.
+    pub fn is_line(&self) -> bool {
+        matches!(self.annotation_type, AnnotationType::MultilineLine(_))
+    }
+
+    pub fn len(&self) -> usize {
+        // Account for usize underflows
+        if self.end_col > self.start_col {
+            self.end_col - self.start_col
+        } else {
+            self.start_col - self.end_col
+        }
+    }
+
+    pub fn has_label(&self) -> bool {
+        if let Some(ref label) = self.label {
+            // Consider labels with no text as effectively not being there
+            // to avoid weird output with unnecessary vertical lines, like:
+            //
+            //     X | fn foo(x: u32) {
+            //       | -------^------
+            //       | |      |
+            //       | |
+            //       |
+            //
+            // Note that this would be the complete output users would see.
+            !label.is_empty()
+        } else {
+            false
+        }
+    }
+
+    pub fn takes_space(&self) -> bool {
+        // Multiline annotations always have to keep vertical space.
+        matches!(
+            self.annotation_type,
+            AnnotationType::MultilineStart(_) | AnnotationType::MultilineEnd(_)
+        )
+    }
+}
+
+#[derive(Debug)]
+pub struct StyledString {
+    pub text: String,
+    pub style: Style,
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Hash, Encodable, Decodable)]
+pub enum Style {
+    MainHeaderMsg,
+    HeaderMsg,
+    LineAndColumn,
+    LineNumber,
+    Quotation,
+    UnderlinePrimary,
+    UnderlineSecondary,
+    LabelPrimary,
+    LabelSecondary,
+    NoStyle,
+    Level(Level),
+    Highlight,
+    Addition,
+    Removal,
+}