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Merged
merged 14 commits into from
Jul 6, 2020
Merged

Suggest Option::map_or(_else) for if let Some { y } else { x } #5301

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bf48a2d
Lint for if let Some(x) = ... instead of Option::map_or
JarredAllen Mar 5, 2020
82f8d4d
Stop linting on macros and correctly use braces for constructs
JarredAllen Apr 25, 2020
b85796f
Properly parenthesize to avoid operator precedence errors
JarredAllen Apr 25, 2020
88c8afd
Handle ref, mut, &, and &mut on the option
JarredAllen May 10, 2020
f73b455
Refactoring
JarredAllen May 10, 2020
7c4de9d
Refactoring pt. 2
JarredAllen May 12, 2020
5e20475
Don't lint if contains a macro
JarredAllen May 31, 2020
5150277
Used clippy to clean itself
JarredAllen May 31, 2020
93f0f5d
Last few tweaks
JarredAllen Jun 12, 2020
ccb9998
Fix compile error from library change
JarredAllen Jun 25, 2020
6ce9812
Clean existing lint code to match new lint
JarredAllen Jun 25, 2020
6e2d55c
Update compile-test to follow new lint
JarredAllen Jun 27, 2020
1c32263
Formatted updates to lints
JarredAllen Jul 1, 2020
c8f700e
Fixed compile errors
JarredAllen Jul 4, 2020
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Refactoring
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@JarredAllen
JarredAllen committed Jul 3, 2020
commit f73b455b99694fbc5ddec38317f705f546729db2
170 changes: 106 additions & 64 deletions clippy_lints/src/option_if_let_else.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use if_chain::if_chain;

use rustc_errors::Applicability;
use rustc_hir::intravisit::{NestedVisitorMap, Visitor};
use rustc_hir::*;
use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, MatchSource, Mutability, PatKind, UnOp};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::hir::map::Map;
use rustc_session::{declare_lint_pass, declare_tool_lint};
Expand Down Expand Up @@ -69,17 +69,12 @@ declare_clippy_lint! {

declare_lint_pass!(OptionIfLetElse => [OPTION_IF_LET_ELSE]);

/// Returns true iff the given expression is the result of calling Result::ok
/// Returns true iff the given expression is the result of calling `Result::ok`
fn is_result_ok(cx: &LateContext<'_, '_>, expr: &'_ Expr<'_>) -> bool {
if_chain! {
if let ExprKind::MethodCall(ref path, _, &[ref receiver]) = &expr.kind;
if path.ident.name.to_ident_string() == "ok";
if match_type(cx, &cx.tables.expr_ty(&receiver), &paths::RESULT);
then {
true
} else {
false
}
if let ExprKind::MethodCall(ref path, _, &[ref receiver]) = &expr.kind {
path.ident.name.to_ident_string() == "ok" && match_type(cx, &cx.tables.expr_ty(&receiver), &paths::RESULT)
} else {
false
}
}

Expand Down Expand Up @@ -136,82 +131,129 @@ fn contains_return_break_continue<'tcx>(expression: &'tcx Expr<'tcx>) -> bool {
recursive_visitor.seen_return_break_continue
}

/// Extracts the body of a given arm. If the arm contains only an expression,
/// then it returns the expression. Otherwise, it returns the entire block
fn extract_body_from_arm<'a>(arm: &'a Arm<'a>) -> Option<&'a Expr<'a>> {
if let ExprKind::Block(
Block {
stmts: statements,
expr: Some(expr),
..
},
_,
) = &arm.body.kind
{
if let [] = statements {
Some(&expr)
} else {
Some(&arm.body)
}
} else {
None
}
}

/// If this is the else body of an if/else expression, then we need to wrap
/// it in curcly braces. Otherwise, we don't.
fn should_wrap_in_braces(cx: &LateContext<'_, '_>, expr: &Expr<'_>) -> bool {
utils::get_enclosing_block(cx, expr.hir_id).map_or(false, |parent| {
if let Some(Expr {
kind:
ExprKind::Match(
_,
arms,
MatchSource::IfDesugar {
contains_else_clause: true,
}
| MatchSource::IfLetDesugar {
contains_else_clause: true,
},
),
..
}) = parent.expr
{
expr.hir_id == arms[1].body.hir_id
} else {
false
}
})
}

fn format_option_in_sugg(
cx: &LateContext<'_, '_>,
cond_expr: &Expr<'_>,
parens_around_option: bool,
as_ref: bool,
as_mut: bool,
) -> String {
format!(
"{}{}{}{}",
if parens_around_option { "(" } else { "" },
Sugg::hir(cx, cond_expr, ".."),
if parens_around_option { ")" } else { "" },
if as_mut {
".as_mut()"
} else if as_ref {
".as_ref()"
} else {
""
}
)
}

/// If this expression is the option if let/else construct we're detecting, then
/// this function returns an OptionIfLetElseOccurence struct with details if
/// this function returns an `OptionIfLetElseOccurence` struct with details if
/// this construct is found, or None if this construct is not found.
fn detect_option_if_let_else<'a>(cx: &LateContext<'_, 'a>, expr: &'a Expr<'a>) -> Option<OptionIfLetElseOccurence> {
if_chain! {
if !utils::in_macro(expr.span); // Don't lint macros, because it behaves weirdly
if let ExprKind::Match(let_body, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
if let ExprKind::Match(cond_expr, arms, MatchSource::IfLetDesugar{contains_else_clause: true}) = &expr.kind;
if arms.len() == 2;
// if type_is_option(cx, &cx.tables.expr_ty(let_body).kind);
if !is_result_ok(cx, let_body); // Don't lint on Result::ok because a different lint does it already
if !is_result_ok(cx, cond_expr); // Don't lint on Result::ok because a different lint does it already
if let PatKind::TupleStruct(struct_qpath, &[inner_pat], _) = &arms[0].pat.kind;
if utils::match_qpath(struct_qpath, &paths::OPTION_SOME);
if let PatKind::Binding(bind_annotation, _, id, _) = &inner_pat.kind;
if !contains_return_break_continue(arms[0].body);
if !contains_return_break_continue(arms[1].body);
then {
let (capture_mut, capture_ref, capture_ref_mut) = match bind_annotation {
BindingAnnotation::Unannotated => (false, false, false),
BindingAnnotation::Mutable => (true, false, false),
BindingAnnotation::Ref => (false, true, false),
BindingAnnotation::RefMut => (false, false, true),
};
let some_body = if let ExprKind::Block(Block { stmts: statements, expr: Some(expr), .. }, _)
= &arms[0].body.kind {
if let &[] = &statements {
expr
} else {
&arms[0].body
}
} else {
return None;
};
let (none_body, method_sugg) = if let ExprKind::Block(Block { stmts: statements, expr: Some(expr), .. }, _)
= &arms[1].body.kind {
if let &[] = &statements {
(expr, "map_or")
} else {
(&arms[1].body, "map_or_else")
}
} else {
return None;
let capture_mut = if bind_annotation == &BindingAnnotation::Mutable { "mut " } else { "" };
let some_body = extract_body_from_arm(&arms[0])?;
let none_body = extract_body_from_arm(&arms[1])?;
let method_sugg = match &none_body.kind {
ExprKind::Block(..) => "map_or_else",
_ => "map_or",
};
let capture_name = id.name.to_ident_string();
let wrap_braces = utils::get_enclosing_block(cx, expr.hir_id).map_or(false, |parent| {
if_chain! {
if let Some(Expr { kind: ExprKind::Match(
_,
arms,
MatchSource::IfDesugar{contains_else_clause: true}
| MatchSource::IfLetDesugar{contains_else_clause: true}),
.. } ) = parent.expr;
if expr.hir_id == arms[1].body.hir_id;
then {
true
} else {
false
}
}
});
let (parens_around_option, as_ref, as_mut, let_body) = match &let_body.kind {
let wrap_braces = should_wrap_in_braces(cx, expr);
let (as_ref, as_mut) = match &cond_expr.kind {
ExprKind::AddrOf(_, Mutability::Not, _) => (true, false),
ExprKind::AddrOf(_, Mutability::Mut, _) => (false, true),
_ => (bind_annotation == &BindingAnnotation::Ref, bind_annotation == &BindingAnnotation::RefMut),
};
let parens_around_option = match &cond_expr.kind {
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@flip1995 flip1995 May 11, 2020

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Oh sorry for not seeing this before. You can use utils::Sugg to build the suggestion, which will take care of the parens automatically.

// Put parens around the option expression if not doing so might
// mess up the order of operations.
ExprKind::Call(..)
| ExprKind::MethodCall(..)
| ExprKind::Loop(..)
| ExprKind::Match(..)
| ExprKind::Block(..)
| ExprKind::Field(..)
| ExprKind::Path(_)
=> (false, capture_ref, capture_ref_mut, let_body),
ExprKind::Unary(UnOp::UnDeref, expr) => (false, capture_ref, capture_ref_mut, expr),
ExprKind::AddrOf(_, mutability, expr) => (false, mutability == &Mutability::Not, mutability == &Mutability::Mut, expr),
_ => (true, capture_ref, capture_ref_mut, let_body),
| ExprKind::Unary(UnOp::UnDeref, _)
| ExprKind::AddrOf(..)
=> false,
_ => true,
};
let cond_expr = match &cond_expr.kind {
// Pointer dereferencing happens automatically, so we can omit it in the suggestion
ExprKind::Unary(UnOp::UnDeref, expr)|ExprKind::AddrOf(_, _, expr) => expr,
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@flip1995 flip1995 May 11, 2020

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Suggested change
ExprKind::Unary(UnOp::UnDeref, expr)|ExprKind::AddrOf(_, _, expr) => expr,
ExprKind::Unary(UnOp::UnDeref, expr) | ExprKind::AddrOf(_, _, expr) => expr,

_ => cond_expr,
};
Some(OptionIfLetElseOccurence {
option: format!("{}{}{}{}", if parens_around_option { "(" } else { "" }, Sugg::hir(cx, let_body, ".."), if parens_around_option { ")" } else { "" }, if as_mut { ".as_mut()" } else if as_ref { ".as_ref()" } else { "" }),
method_sugg: format!("{}", method_sugg),
some_expr: format!("|{}{}{}| {}", if false { "ref " } else { "" }, if capture_mut { "mut " } else { "" }, capture_name, Sugg::hir(cx, some_body, "..")),
option: format_option_in_sugg(cx, cond_expr, parens_around_option, as_ref, as_mut),
method_sugg: method_sugg.to_string(),
some_expr: format!("|{}{}| {}", capture_mut, capture_name, Sugg::hir(cx, some_body, "..")),
none_expr: format!("{}{}", if method_sugg == "map_or" { "" } else { "|| " }, Sugg::hir(cx, none_body, "..")),
wrap_braces,
})
Expand Down
18 changes: 3 additions & 15 deletions tests/ui/option_if_let_else.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,27 +20,15 @@ fn else_if_option(string: Option<&str>) -> Option<(bool, &str)> {
}

fn unop_bad(string: &Option<&str>, mut num: Option<i32>) {
let _ = if let Some(s) = *string {
s.len()
} else {
0
};
let _ = if let Some(s) = &num {
s
} else {
&0
};
let _ = if let Some(s) = *string { s.len() } else { 0 };
let _ = if let Some(s) = &num { s } else { &0 };
let _ = if let Some(s) = &mut num {
*s += 1;
s
} else {
&mut 0
};
let _ = if let Some(ref s) = num {
s
} else {
&0
};
let _ = if let Some(ref s) = num { s } else { &0 };
let _ = if let Some(mut s) = num {
s += 1;
s
Expand Down
43 changes: 14 additions & 29 deletions tests/ui/option_if_let_else.stderr
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Expand Up @@ -24,27 +24,17 @@ LL | | }
error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:23:13
|
LL | let _ = if let Some(s) = *string {
| _____________^
LL | | s.len()
LL | | } else {
LL | | 0
LL | | };
| |_____^ help: try: `string.map_or(0, |s| s.len())`
LL | let _ = if let Some(s) = *string { s.len() } else { 0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `string.map_or(0, |s| s.len())`

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:28:13
--> $DIR/option_if_let_else.rs:24:13
|
LL | let _ = if let Some(s) = &num {
| _____________^
LL | | s
LL | | } else {
LL | | &0
LL | | };
| |_____^ help: try: `num.as_ref().map_or(&0, |s| s)`
LL | let _ = if let Some(s) = &num { s } else { &0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:33:13
--> $DIR/option_if_let_else.rs:25:13
|
LL | let _ = if let Some(s) = &mut num {
| _____________^
Expand All @@ -64,18 +54,13 @@ LL | });
|

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:39:13
--> $DIR/option_if_let_else.rs:31:13
|
LL | let _ = if let Some(ref s) = num {
| _____________^
LL | | s
LL | | } else {
LL | | &0
LL | | };
| |_____^ help: try: `num.as_ref().map_or(&0, |s| s)`
LL | let _ = if let Some(ref s) = num { s } else { &0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:44:13
--> $DIR/option_if_let_else.rs:32:13
|
LL | let _ = if let Some(mut s) = num {
| _____________^
Expand All @@ -95,7 +80,7 @@ LL | });
|

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:50:13
--> $DIR/option_if_let_else.rs:38:13
|
LL | let _ = if let Some(ref mut s) = num {
| _____________^
Expand All @@ -115,7 +100,7 @@ LL | });
|

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:59:5
--> $DIR/option_if_let_else.rs:47:5
|
LL | / if let Some(x) = arg {
LL | | let y = x * x;
Expand All @@ -134,7 +119,7 @@ LL | })
|

error: use Option::map_or_else instead of an if let/else
--> $DIR/option_if_let_else.rs:68:13
--> $DIR/option_if_let_else.rs:56:13
|
LL | let _ = if let Some(x) = arg {
| _____________^
Expand All @@ -157,7 +142,7 @@ LL | }, |x| x * x * x * x);
|

error: use Option::map_or instead of an if let/else
--> $DIR/option_if_let_else.rs:97:13
--> $DIR/option_if_let_else.rs:85:13
|
LL | let _ = if let Some(x) = optional { x + 2 } else { 5 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `optional.map_or(5, |x| x + 2)`
Expand Down