rust-clippy/clippy_lints/src/formatting.rs

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use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_note};
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use clippy_utils::differing_macro_contexts;
use clippy_utils::source::snippet_opt;
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use if_chain::if_chain;
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use rustc_ast::ast::{BinOpKind, Block, Expr, ExprKind, StmtKind, UnOp};
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use rustc_lint::{EarlyContext, EarlyLintPass};
use rustc_middle::lint::in_external_macro;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::source_map::Span;
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declare_clippy_lint! {
/// **What it does:** Checks for use of the non-existent `=*`, `=!` and `=-`
/// operators.
///
/// **Why is this bad?** This is either a typo of `*=`, `!=` or `-=` or
/// confusing.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// a =- 42; // confusing, should it be `a -= 42` or `a = -42`?
/// ```
pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
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style,
"suspicious formatting of `*=`, `-=` or `!=`"
}
declare_clippy_lint! {
/// **What it does:** Checks the formatting of a unary operator on the right hand side
/// of a binary operator. It lints if there is no space between the binary and unary operators,
/// but there is a space between the unary and its operand.
///
/// **Why is this bad?** This is either a typo in the binary operator or confusing.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// if foo <- 30 { // this should be `foo < -30` but looks like a different operator
/// }
///
/// if foo &&! bar { // this should be `foo && !bar` but looks like a different operator
/// }
/// ```
pub SUSPICIOUS_UNARY_OP_FORMATTING,
style,
"suspicious formatting of unary `-` or `!` on the RHS of a BinOp"
}
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declare_clippy_lint! {
/// **What it does:** Checks for formatting of `else`. It lints if the `else`
/// is followed immediately by a newline or the `else` seems to be missing.
///
/// **Why is this bad?** This is probably some refactoring remnant, even if the
/// code is correct, it might look confusing.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// if foo {
/// } { // looks like an `else` is missing here
/// }
///
/// if foo {
/// } if bar { // looks like an `else` is missing here
/// }
///
/// if foo {
/// } else
///
/// { // this is the `else` block of the previous `if`, but should it be?
/// }
///
/// if foo {
/// } else
///
/// if bar { // this is the `else` block of the previous `if`, but should it be?
/// }
/// ```
pub SUSPICIOUS_ELSE_FORMATTING,
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style,
"suspicious formatting of `else`"
}
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declare_clippy_lint! {
/// **What it does:** Checks for possible missing comma in an array. It lints if
/// an array element is a binary operator expression and it lies on two lines.
///
/// **Why is this bad?** This could lead to unexpected results.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust,ignore
/// let a = &[
/// -1, -2, -3 // <= no comma here
/// -4, -5, -6
/// ];
/// ```
pub POSSIBLE_MISSING_COMMA,
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correctness,
"possible missing comma in array"
}
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declare_lint_pass!(Formatting => [
SUSPICIOUS_ASSIGNMENT_FORMATTING,
SUSPICIOUS_UNARY_OP_FORMATTING,
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SUSPICIOUS_ELSE_FORMATTING,
POSSIBLE_MISSING_COMMA
]);
impl EarlyLintPass for Formatting {
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fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
for w in block.stmts.windows(2) {
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if let (StmtKind::Expr(first), StmtKind::Expr(second) | StmtKind::Semi(second)) = (&w[0].kind, &w[1].kind) {
check_missing_else(cx, first, second);
}
}
}
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fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
check_assign(cx, expr);
check_unop(cx, expr);
check_else(cx, expr);
check_array(cx, expr);
}
}
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/// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
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fn check_assign(cx: &EarlyContext<'_>, expr: &Expr) {
if let ExprKind::Assign(ref lhs, ref rhs, _) = expr.kind {
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if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion() {
let eq_span = lhs.span.between(rhs.span);
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if let ExprKind::Unary(op, ref sub_rhs) = rhs.kind {
if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
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let op = UnOp::to_string(op);
let eqop_span = lhs.span.between(sub_rhs.span);
if eq_snippet.ends_with('=') {
span_lint_and_note(
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cx,
SUSPICIOUS_ASSIGNMENT_FORMATTING,
eqop_span,
&format!(
"this looks like you are trying to use `.. {op}= ..`, but you \
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really are doing `.. = ({op} ..)`",
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op = op
),
None,
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&format!("to remove this lint, use either `{op}=` or `= {op}`", op = op),
);
}
}
}
}
}
}
/// Implementation of the `SUSPICIOUS_UNARY_OP_FORMATTING` lint.
fn check_unop(cx: &EarlyContext<'_>, expr: &Expr) {
if_chain! {
if let ExprKind::Binary(ref binop, ref lhs, ref rhs) = expr.kind;
if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion();
// span between BinOp LHS and RHS
let binop_span = lhs.span.between(rhs.span);
// if RHS is a UnOp
if let ExprKind::Unary(op, ref un_rhs) = rhs.kind;
// from UnOp operator to UnOp operand
let unop_operand_span = rhs.span.until(un_rhs.span);
if let Some(binop_snippet) = snippet_opt(cx, binop_span);
if let Some(unop_operand_snippet) = snippet_opt(cx, unop_operand_span);
let binop_str = BinOpKind::to_string(&binop.node);
// no space after BinOp operator and space after UnOp operator
if binop_snippet.ends_with(binop_str) && unop_operand_snippet.ends_with(' ');
then {
let unop_str = UnOp::to_string(op);
let eqop_span = lhs.span.between(un_rhs.span);
span_lint_and_help(
cx,
SUSPICIOUS_UNARY_OP_FORMATTING,
eqop_span,
&format!(
"by not having a space between `{binop}` and `{unop}` it looks like \
`{binop}{unop}` is a single operator",
binop = binop_str,
unop = unop_str
),
None,
&format!(
"put a space between `{binop}` and `{unop}` and remove the space after `{unop}`",
binop = binop_str,
unop = unop_str
),
);
}
}
}
/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else`.
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fn check_else(cx: &EarlyContext<'_>, expr: &Expr) {
if_chain! {
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if let ExprKind::If(_, then, Some(else_)) = &expr.kind;
if is_block(else_) || is_if(else_);
if !differing_macro_contexts(then.span, else_.span);
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if !then.span.from_expansion() && !in_external_macro(cx.sess, expr.span);
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// workaround for rust-lang/rust#43081
if expr.span.lo().0 != 0 && expr.span.hi().0 != 0;
// this will be a span from the closing } of the “then” block (excluding) to
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// the “if” of the “else if” block (excluding)
let else_span = then.span.between(else_.span);
// the snippet should look like " else \n " with maybe comments anywhere
// its bad when there is a \n after the “else”
if let Some(else_snippet) = snippet_opt(cx, else_span);
if let Some(else_pos) = else_snippet.find("else");
if else_snippet[else_pos..].contains('\n');
let else_desc = if is_if(else_) { "if" } else { "{..}" };
then {
span_lint_and_note(
cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
&format!("this is an `else {}` but the formatting might hide it", else_desc),
None,
&format!(
"to remove this lint, remove the `else` or remove the new line between \
`else` and `{}`",
else_desc,
),
);
}
}
}
#[must_use]
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fn has_unary_equivalent(bin_op: BinOpKind) -> bool {
// &, *, -
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bin_op == BinOpKind::And || bin_op == BinOpKind::Mul || bin_op == BinOpKind::Sub
}
fn indentation(cx: &EarlyContext<'_>, span: Span) -> usize {
cx.sess.source_map().lookup_char_pos(span.lo()).col.0
}
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/// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
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fn check_array(cx: &EarlyContext<'_>, expr: &Expr) {
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if let ExprKind::Array(ref array) = expr.kind {
for element in array {
if_chain! {
if let ExprKind::Binary(ref op, ref lhs, _) = element.kind;
if has_unary_equivalent(op.node) && !differing_macro_contexts(lhs.span, op.span);
let space_span = lhs.span.between(op.span);
if let Some(space_snippet) = snippet_opt(cx, space_span);
let lint_span = lhs.span.with_lo(lhs.span.hi());
if space_snippet.contains('\n');
if indentation(cx, op.span) <= indentation(cx, lhs.span);
then {
span_lint_and_note(
cx,
POSSIBLE_MISSING_COMMA,
lint_span,
"possibly missing a comma here",
None,
"to remove this lint, add a comma or write the expr in a single line",
);
}
}
}
}
}
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fn check_missing_else(cx: &EarlyContext<'_>, first: &Expr, second: &Expr) {
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if !differing_macro_contexts(first.span, second.span)
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&& !first.span.from_expansion()
&& is_if(first)
&& (is_block(second) || is_if(second))
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{
// where the else would be
let else_span = first.span.between(second.span);
if let Some(else_snippet) = snippet_opt(cx, else_span) {
if !else_snippet.contains('\n') {
let (looks_like, next_thing) = if is_if(second) {
("an `else if`", "the second `if`")
} else {
("an `else {..}`", "the next block")
};
span_lint_and_note(
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cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
&format!("this looks like {} but the `else` is missing", looks_like),
None,
&format!(
"to remove this lint, add the missing `else` or add a new line before {}",
next_thing,
),
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);
}
}
}
}
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fn is_block(expr: &Expr) -> bool {
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matches!(expr.kind, ExprKind::Block(..))
}
/// Check if the expression is an `if` or `if let`
fn is_if(expr: &Expr) -> bool {
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matches!(expr.kind, ExprKind::If(..))
}