src/librustc_ast_borrowck/cfg/graphviz.rs

/// This module provides linkage between `rustc::middle::graph` and
/// libgraphviz traits.

use crate::cfg;
use rustc::hir;
use rustc::ty::TyCtxt;

pub(crate) type Node<'a> = (cfg::CFGIndex, &'a cfg::CFGNode);
pub(crate) type Edge<'a> = &'a cfg::CFGEdge;

pub struct LabelledCFG<'a, 'tcx> {
    pub tcx: TyCtxt<'tcx>,
    pub cfg: &'a cfg::CFG,
    pub name: String,
    /// `labelled_edges` controls whether we emit labels on the edges.
    pub labelled_edges: bool,
}

impl<'a, 'tcx> LabelledCFG<'a, 'tcx> {
    fn local_id_to_string(&self, local_id: hir::ItemLocalId) -> String {
        assert!(self.cfg.owner_def_id.is_local());
        let hir_id = hir::HirId {
            owner: self.tcx.hir().def_index_to_hir_id(self.cfg.owner_def_id.index).owner,
            local_id
        };
        let s = self.tcx.hir().node_to_string(hir_id);

        // Replacing newlines with `\\l` causes each line to be left-aligned,
        // improving presentation of (long) pretty-printed expressions.
        if s.contains("\n") {
            let mut s = s.replace("\n", "\\l");
            // Apparently left-alignment applies to the line that precedes
            // `\l`, not the line that follows; so, add `\l` at end of string
            // if not already present, ensuring last line gets left-aligned
            // as well.
            let mut last_two: Vec<_> =
                s.chars().rev().take(2).collect();
            last_two.reverse();
            if last_two != ['\\', 'l'] {
                s.push_str("\\l");
            }
            s
        } else {
            s
        }
    }
}

impl<'a, 'hir> dot::Labeller<'a> for LabelledCFG<'a, 'hir> {
    type Node = Node<'a>;
    type Edge = Edge<'a>;
    fn graph_id(&'a self) -> dot::Id<'a> { dot::Id::new(&self.name[..]).unwrap() }

    fn node_id(&'a self, &(i,_): &Node<'a>) -> dot::Id<'a> {
        dot::Id::new(format!("N{}", i.node_id())).unwrap()
    }

    fn node_label(&'a self, &(i, n): &Node<'a>) -> dot::LabelText<'a> {
        if i == self.cfg.entry {
            dot::LabelText::LabelStr("entry".into())
        } else if i == self.cfg.exit {
            dot::LabelText::LabelStr("exit".into())
        } else if n.data.id() == hir::DUMMY_ITEM_LOCAL_ID {
            dot::LabelText::LabelStr("(dummy_node)".into())
        } else {
            let s = self.local_id_to_string(n.data.id());
            dot::LabelText::EscStr(s.into())
        }
    }

    fn edge_label(&self, e: &Edge<'a>) -> dot::LabelText<'a> {
        let mut label = String::new();
        if !self.labelled_edges {
            return dot::LabelText::EscStr(label.into());
        }
        let mut put_one = false;
        for (i, &id) in e.data.exiting_scopes.iter().enumerate() {
            if put_one {
                label.push_str(",\\l");
            } else {
                put_one = true;
            }
            let s = self.local_id_to_string(id);
            label.push_str(&format!("exiting scope_{} {}",
                                   i,
                                   &s[..]));
        }
        dot::LabelText::EscStr(label.into())
    }
}

impl<'a> dot::GraphWalk<'a> for &'a cfg::CFG {
    type Node = Node<'a>;
    type Edge = Edge<'a>;
    fn nodes(&'a self) -> dot::Nodes<'a, Node<'a>> {
        let v: Vec<_> = self.graph.enumerated_nodes().collect();
        v.into()
    }
    fn edges(&'a self) -> dot::Edges<'a, Edge<'a>> {
        self.graph.all_edges().iter().collect()
    }
    fn source(&'a self, edge: &Edge<'a>) -> Node<'a> {
        let i = edge.source();
        (i, self.graph.node(i))
    }
    fn target(&'a self, edge: &Edge<'a>) -> Node<'a> {
        let i = edge.target();
        (i, self.graph.node(i))
    }
}

impl<'a, 'hir> dot::GraphWalk<'a> for LabelledCFG<'a, 'hir> {
    type Node = Node<'a>;
    type Edge = Edge<'a>;
    fn nodes(&'a self) -> dot::Nodes<'a, Node<'a>> { self.cfg.nodes() }
    fn edges(&'a self) -> dot::Edges<'a, Edge<'a>> { self.cfg.edges() }
    fn source(&'a self, edge: &Edge<'a>) -> Node<'a> { self.cfg.source(edge) }
    fn target(&'a self, edge: &Edge<'a>) -> Node<'a> { self.cfg.target(edge) }
}