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Add lints suggesting map_or() and map_or_else()

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In accordance with the latter lint, replace map().unwrap_or_else() in
src/mut_mut.rs with map_or_else()
This commit is contained in:
Devon Hollowood 2015-11-22 21:48:19 -08:00
parent 84ad2be1df
commit 443e4556c2
5 changed files with 136 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

2
src/lib.rs
View file

@ -156,6 +156,8 @@ pub fn plugin_registrar(reg: &mut Registry) {
matches::MATCH_REF_PATS,
matches::SINGLE_MATCH,
methods::OK_EXPECT,
methods::OPTION_MAP_UNWRAP_OR,
methods::OPTION_MAP_UNWRAP_OR_ELSE,
methods::SHOULD_IMPLEMENT_TRAIT,
methods::STR_TO_STRING,
methods::STRING_TO_STRING,

72
src/methods.rs
View file

@ -5,7 +5,7 @@ use rustc::middle::subst::{Subst, TypeSpace};
use std::iter;
use std::borrow::Cow;
use utils::{snippet, span_lint, match_path, match_type, walk_ptrs_ty_depth,
use utils::{snippet, span_lint, span_note_and_lint, match_path, match_type, walk_ptrs_ty_depth,
walk_ptrs_ty};
use utils::{OPTION_PATH, RESULT_PATH, STRING_PATH};
@ -34,12 +34,18 @@ declare_lint!(pub WRONG_PUB_SELF_CONVENTION, Allow,
declare_lint!(pub OK_EXPECT, Warn,
"using `ok().expect()`, which gives worse error messages than \
calling `expect` directly on the Result");
declare_lint!(pub OPTION_MAP_UNWRAP_OR, Warn,
"using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
`map_or(a, f)`)");
declare_lint!(pub OPTION_MAP_UNWRAP_OR_ELSE, Warn,
"using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
`map_or_else(g, f)`)");
impl LintPass for MethodsPass {
fn get_lints(&self) -> LintArray {
lint_array!(OPTION_UNWRAP_USED, RESULT_UNWRAP_USED, STR_TO_STRING, STRING_TO_STRING,
SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION, OK_EXPECT)
SHOULD_IMPLEMENT_TRAIT, WRONG_SELF_CONVENTION, OK_EXPECT, OPTION_MAP_UNWRAP_OR,
OPTION_MAP_UNWRAP_OR_ELSE)
}
}
@ -92,6 +98,66 @@ impl LateLintPass for MethodsPass {
}
}
}
// check Option.map(_).unwrap_or(_)
else if name.node.as_str() == "unwrap_or" {
if let ExprMethodCall(ref inner_name, _, ref inner_args) = args[0].node {
if inner_name.node.as_str() == "map"
&& match_type(cx, cx.tcx.expr_ty(&inner_args[0]), &OPTION_PATH) {
// 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 args to map() and unwrap_or()
let map_arg = snippet(cx, inner_args[1].span, "..");
let unwrap_arg = snippet(cx, args[1].span, "..");
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or() have the same span
let multiline = map_arg.lines().count() > 1
|| unwrap_arg.lines().count() > 1;
let same_span = inner_args[1].span.expn_id == args[1].span.expn_id;
if same_span && !multiline {
span_note_and_lint(
cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span,
&format!("replace this with map_or({1}, {0})",
map_arg, unwrap_arg)
);
}
else if same_span && multiline {
span_lint(cx, OPTION_MAP_UNWRAP_OR, expr.span, msg);
};
}
}
}
// check Option.map(_).unwrap_or_else(_)
else if name.node.as_str() == "unwrap_or_else" {
if let ExprMethodCall(ref inner_name, _, ref inner_args) = args[0].node {
if inner_name.node.as_str() == "map"
&& match_type(cx, cx.tcx.expr_ty(&inner_args[0]), &OPTION_PATH) {
// lint message
let msg =
"called `map(f).unwrap_or_else(g)` on an Option value. This can be \
done more directly by calling `map_or_else(g, f)` instead";
// get args to map() and unwrap_or_else()
let map_arg = snippet(cx, inner_args[1].span, "..");
let unwrap_arg = snippet(cx, args[1].span, "..");
// lint, with note if neither arg is > 1 line and both map() and
// unwrap_or_else() have the same span
let multiline = map_arg.lines().count() > 1
|| unwrap_arg.lines().count() > 1;
let same_span = inner_args[1].span.expn_id == args[1].span.expn_id;
if same_span && !multiline {
span_note_and_lint(
cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg, expr.span,
&format!("replace this with map_or_else({1}, {0})",
map_arg, unwrap_arg)
);
}
else if same_span && multiline {
span_lint(cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg);
};
}
}
}
}
}

23
src/mut_mut.rs
View file

@ -39,17 +39,20 @@ fn check_expr_mut(cx: &LateContext, expr: &Expr) {
}
unwrap_addr(expr).map_or((), |e| {
unwrap_addr(e).map(|_| {
span_lint(cx, MUT_MUT, expr.span,
"generally you want to avoid `&mut &mut _` if possible")
}).unwrap_or_else(|| {
if let TyRef(_, TypeAndMut{ty: _, mutbl: MutMutable}) =
cx.tcx.expr_ty(e).sty {
span_lint(cx, MUT_MUT, expr.span,
"this expression mutably borrows a mutable reference. \
Consider reborrowing")
unwrap_addr(e).map_or_else(
|| {
if let TyRef(_, TypeAndMut{ty: _, mutbl: MutMutable}) =
cx.tcx.expr_ty(e).sty {
span_lint(cx, MUT_MUT, expr.span,
"this expression mutably borrows a mutable reference. \
Consider reborrowing")
}
})
},
|_| {
span_lint(cx, MUT_MUT, expr.span,
"generally you want to avoid `&mut &mut _` if possible")
}
)
})
}