123 lines
4.2 KiB
Rust
123 lines
4.2 KiB
Rust
use crate::utils::paths;
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use crate::utils::{is_copy, match_type, snippet, span_lint, span_note_and_lint};
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use rustc::hir::intravisit::{walk_path, NestedVisitorMap, Visitor};
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use rustc::hir::{self, *};
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use rustc::lint::LateContext;
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use rustc_data_structures::fx::FxHashSet;
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use syntax_pos::symbol::Symbol;
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use super::OPTION_MAP_UNWRAP_OR;
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/// lint use of `map().unwrap_or()` for `Option`s
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pub(super) fn lint<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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expr: &hir::Expr<'_>,
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map_args: &'tcx [hir::Expr<'_>],
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unwrap_args: &'tcx [hir::Expr<'_>],
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) {
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// lint if the caller of `map()` is an `Option`
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if match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION) {
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if !is_copy(cx, cx.tables.expr_ty(&unwrap_args[1])) {
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// Do not lint if the `map` argument uses identifiers in the `map`
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// argument that are also used in the `unwrap_or` argument
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let mut unwrap_visitor = UnwrapVisitor {
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cx,
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identifiers: FxHashSet::default(),
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};
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unwrap_visitor.visit_expr(&unwrap_args[1]);
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let mut map_expr_visitor = MapExprVisitor {
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cx,
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identifiers: unwrap_visitor.identifiers,
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found_identifier: false,
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};
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map_expr_visitor.visit_expr(&map_args[1]);
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if map_expr_visitor.found_identifier {
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return;
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}
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}
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// get snippets for args to map() and unwrap_or()
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let map_snippet = snippet(cx, map_args[1].span, "..");
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let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
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// lint message
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// comparing the snippet from source to raw text ("None") below is safe
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// because we already have checked the type.
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let arg = if unwrap_snippet == "None" { "None" } else { "a" };
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let suggest = if unwrap_snippet == "None" {
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"and_then(f)"
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} else {
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"map_or(a, f)"
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};
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let msg = &format!(
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"called `map(f).unwrap_or({})` on an Option value. \
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This can be done more directly by calling `{}` instead",
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arg, suggest
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);
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// lint, with note if neither arg is > 1 line and both map() and
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// unwrap_or() have the same span
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let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
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let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
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if same_span && !multiline {
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let suggest = if unwrap_snippet == "None" {
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format!("and_then({})", map_snippet)
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} else {
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format!("map_or({}, {})", unwrap_snippet, map_snippet)
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};
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let note = format!(
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"replace `map({}).unwrap_or({})` with `{}`",
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map_snippet, unwrap_snippet, suggest
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);
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span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, ¬e);
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} else if same_span && multiline {
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span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
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};
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}
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}
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struct UnwrapVisitor<'a, 'tcx> {
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cx: &'a LateContext<'a, 'tcx>,
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identifiers: FxHashSet<Symbol>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for UnwrapVisitor<'a, 'tcx> {
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fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
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self.identifiers.insert(ident(path));
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walk_path(self, path);
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}
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::All(&self.cx.tcx.hir())
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}
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}
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struct MapExprVisitor<'a, 'tcx> {
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cx: &'a LateContext<'a, 'tcx>,
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identifiers: FxHashSet<Symbol>,
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found_identifier: bool,
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}
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impl<'a, 'tcx> Visitor<'tcx> for MapExprVisitor<'a, 'tcx> {
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fn visit_path(&mut self, path: &'tcx Path, _id: HirId) {
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if self.identifiers.contains(&ident(path)) {
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self.found_identifier = true;
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return;
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}
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walk_path(self, path);
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}
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::All(&self.cx.tcx.hir())
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}
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}
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fn ident(path: &Path) -> Symbol {
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path.segments
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.last()
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.expect("segments should be composed of at least 1 element")
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.ident
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.name
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}
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