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Merge pull request #2112 from topecongiro/issue-2109

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Add a suggestion to replace `map(f).unwrap_or(None)` with `and_then(f)`.
This commit is contained in:
Oliver Schneider 2017-10-08 11:51:15 +02:00 • committed by GitHub
commit a54baad4fa
3 changed files with 292 additions and 245 deletions
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36
clippy_lints/src/methods.rs
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@ -1150,29 +1150,37 @@ fn lint_ok_expect(cx: &LateContext, expr: &hir::Expr, ok_args: &[hir::Expr]) {
fn lint_map_unwrap_or(cx: &LateContext, expr: &hir::Expr, map_args: &[hir::Expr], unwrap_args: &[hir::Expr]) {
// lint if the caller of `map()` is an `Option`
if match_type(cx, cx.tables.expr_ty(&map_args[0]), &paths::OPTION) {
// lint message
let msg = "called `map(f).unwrap_or(a)` on an Option value. This can be done more directly by calling \
`map_or(a, f)` instead";
// get snippets for args to map() and unwrap_or()
let map_snippet = snippet(cx, map_args[1].span, "..");
let unwrap_snippet = snippet(cx, unwrap_args[1].span, "..");
// lint message
// comparing the snippet from source to raw text ("None") below is safe
// because we already have checked the type.
let arg = if unwrap_snippet == "None" { "None" } else { "a" };
let suggest = if unwrap_snippet == "None" { "and_then(f)" } else { "map_or(a, f)" };
let msg = &format!(
"called `map(f).unwrap_or({})` on an Option value. \
This can be done more directly by calling `{}` instead",
arg,
suggest
);
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or() have the same span
let multiline = map_snippet.lines().count() > 1 || unwrap_snippet.lines().count() > 1;
let same_span = map_args[1].span.ctxt() == unwrap_args[1].span.ctxt();
if same_span && !multiline {
span_note_and_lint(
cx,
OPTION_MAP_UNWRAP_OR,
expr.span,
msg,
expr.span,
&format!(
"replace `map({0}).unwrap_or({1})` with `map_or({1}, {0})`",
map_snippet,
unwrap_snippet
),
let suggest = if unwrap_snippet == "None" {
format!("and_then({})", map_snippet)
} else {
format!("map_or({}, {})", unwrap_snippet, map_snippet)
};
let note = format!(
"replace `map({}).unwrap_or({})` with `{}`",
map_snippet,
unwrap_snippet,
suggest
);
span_note_and_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span, &note);
} else if same_span && multiline {
span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
};