Add lint for redundant pattern matching for explicit return boolean

This commit is contained in:
CYBAI 2018-10-07 21:36:42 +08:00
parent dae7abb16b
commit 3b7c88888b
3 changed files with 244 additions and 40 deletions

View file

@ -11,6 +11,8 @@
use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use crate::rustc::{declare_tool_lint, lint_array};
use crate::rustc::hir::*;
use crate::syntax::ptr::P;
use crate::syntax::ast::LitKind;
use crate::utils::{match_qpath, paths, snippet, span_lint_and_then};
use crate::rustc_errors::Applicability;
@ -58,46 +60,164 @@ impl LintPass for Pass {
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
#[allow(clippy::similar_names)]
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let ExprKind::Match(ref op, ref arms, MatchSource::IfLetDesugar { .. }) = expr.node {
if arms[0].pats.len() == 1 {
let good_method = match arms[0].pats[0].node {
PatKind::TupleStruct(ref path, ref pats, _) if pats.len() == 1 => {
if let PatKind::Wild = pats[0].node {
if match_qpath(path, &paths::RESULT_OK) {
"is_ok()"
} else if match_qpath(path, &paths::RESULT_ERR) {
"is_err()"
} else if match_qpath(path, &paths::OPTION_SOME) {
"is_some()"
} else {
return;
}
} else {
return;
}
},
PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()",
_ => return,
};
span_lint_and_then(
cx,
IF_LET_REDUNDANT_PATTERN_MATCHING,
arms[0].pats[0].span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|db| {
let span = expr.span.to(op.span);
db.span_suggestion_with_applicability(
span,
"try this",
format!("if {}.{}", snippet(cx, op.span, "_"), good_method),
Applicability::MachineApplicable, // snippet
);
},
);
if let ExprKind::Match(ref op, ref arms, ref match_source) = expr.node {
match match_source {
MatchSource::Normal => find_sugg_for_match(cx, expr, op, arms),
MatchSource::IfLetDesugar { .. } => find_sugg_for_if_let(cx, expr, op, arms),
_ => return,
}
}
}
}
fn find_sugg_for_if_let<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx Expr,
op: &P<Expr>,
arms: &HirVec<Arm>
) {
if arms[0].pats.len() == 1 {
let good_method = match arms[0].pats[0].node {
PatKind::TupleStruct(ref path, ref pats, _) if pats.len() == 1 => {
if let PatKind::Wild = pats[0].node {
if match_qpath(path, &paths::RESULT_OK) {
"is_ok()"
} else if match_qpath(path, &paths::RESULT_ERR) {
"is_err()"
} else if match_qpath(path, &paths::OPTION_SOME) {
"is_some()"
} else {
return;
}
} else {
return;
}
},
PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()",
_ => return,
};
span_lint_and_then(
cx,
IF_LET_REDUNDANT_PATTERN_MATCHING,
arms[0].pats[0].span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|db| {
let span = expr.span.to(op.span);
db.span_suggestion_with_applicability(
span,
"try this",
format!("if {}.{}", snippet(cx, op.span, "_"), good_method),
Applicability::MachineApplicable, // snippet
);
},
);
} else {
return;
}
}
fn find_sugg_for_match<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &'tcx Expr,
op: &P<Expr>,
arms: &HirVec<Arm>
) {
if arms.len() == 2 {
let node_pair = (&arms[0].pats[0].node, &arms[1].pats[0].node);
let found_good_method = match node_pair {
(
PatKind::TupleStruct(ref path_left, ref pats_left, _),
PatKind::TupleStruct(ref path_right, ref pats_right, _)
) if pats_left.len() == 1 && pats_right.len() == 1 => {
if let (PatKind::Wild, PatKind::Wild) = (&pats_left[0].node, &pats_right[0].node) {
find_good_method_for_match(
arms,
path_left,
path_right,
&paths::RESULT_OK,
&paths::RESULT_ERR,
"is_ok()",
"is_err()"
)
} else {
None
}
},
(
PatKind::TupleStruct(ref path_left, ref pats, _),
PatKind::Path(ref path_right)
) | (
PatKind::Path(ref path_left),
PatKind::TupleStruct(ref path_right, ref pats, _)
) if pats.len() == 1 => {
if let PatKind::Wild = pats[0].node {
find_good_method_for_match(
arms,
path_left,
path_right,
&paths::OPTION_SOME,
&paths::OPTION_NONE,
"is_some()",
"is_none()"
)
} else {
None
}
},
_ => None,
};
if let Some(good_method) = found_good_method {
span_lint_and_then(
cx,
IF_LET_REDUNDANT_PATTERN_MATCHING,
expr.span,
&format!("redundant pattern matching, consider using `{}`", good_method),
|db| {
let span = expr.span.to(op.span);
db.span_suggestion_with_applicability(
span,
"try this",
format!("{}.{}", snippet(cx, op.span, "_"), good_method),
Applicability::MachineApplicable, // snippet
);
},
);
}
} else {
return;
}
}
fn find_good_method_for_match<'a>(
arms: &HirVec<Arm>,
path_left: &QPath,
path_right: &QPath,
expected_left: &[&str],
expected_right: &[&str],
should_be_left: &'a str,
should_be_right: &'a str
) -> Option<&'a str> {
let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
(&(*arms[0].body).node, &(*arms[1].body).node)
} else if match_qpath(path_right, expected_left) && match_qpath(path_left, expected_right) {
(&(*arms[1].body).node, &(*arms[0].body).node)
} else {
return None;
};
match body_node_pair {
(ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => {
match (&lit_left.node, &lit_right.node) {
(LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
(LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
_ => None,
}
},
_ => None,
}
}

View file

@ -42,4 +42,34 @@ fn main() {
if let Ok(x) = Ok::<i32,i32>(42) {
println!("{}", x);
}
match Ok::<i32, i32>(42) {
Ok(_) => true,
Err(_) => false,
};
match Ok::<i32, i32>(42) {
Ok(_) => false,
Err(_) => true,
};
match Err::<i32, i32>(42) {
Ok(_) => false,
Err(_) => true,
};
match Err::<i32, i32>(42) {
Ok(_) => true,
Err(_) => false,
};
match Some(42) {
Some(_) => true,
None => false,
};
match None::<()> {
Some(_) => false,
None => true,
};
}

View file

@ -30,5 +30,59 @@ error: redundant pattern matching, consider using `is_some()`
28 | | }
| |_____- help: try this: `if Some(42).is_some()`
error: aborting due to 4 previous errors
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/if_let_redundant_pattern_matching.rs:46:5
|
46 | / match Ok::<i32, i32>(42) {
47 | | Ok(_) => true,
48 | | Err(_) => false,
49 | | };
| |_____^ help: try this: `Ok::<i32, i32>(42).is_ok()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/if_let_redundant_pattern_matching.rs:51:5
|
51 | / match Ok::<i32, i32>(42) {
52 | | Ok(_) => false,
53 | | Err(_) => true,
54 | | };
| |_____^ help: try this: `Ok::<i32, i32>(42).is_err()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/if_let_redundant_pattern_matching.rs:56:5
|
56 | / match Err::<i32, i32>(42) {
57 | | Ok(_) => false,
58 | | Err(_) => true,
59 | | };
| |_____^ help: try this: `Err::<i32, i32>(42).is_err()`
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/if_let_redundant_pattern_matching.rs:61:5
|
61 | / match Err::<i32, i32>(42) {
62 | | Ok(_) => true,
63 | | Err(_) => false,
64 | | };
| |_____^ help: try this: `Err::<i32, i32>(42).is_ok()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/if_let_redundant_pattern_matching.rs:66:5
|
66 | / match Some(42) {
67 | | Some(_) => true,
68 | | None => false,
69 | | };
| |_____^ help: try this: `Some(42).is_some()`
error: redundant pattern matching, consider using `is_none()`
--> $DIR/if_let_redundant_pattern_matching.rs:71:5
|
71 | / match None::<()> {
72 | | Some(_) => false,
73 | | None => true,
74 | | };
| |_____^ help: try this: `None::<()>.is_none()`
error: aborting due to 10 previous errors