clippy_lints/src/formatting.rs

   1 use crate::utils::{differing_macro_contexts, snippet_opt, span_help_and_lint, span_note_and_lint};
   2 use if_chain::if_chain;
   3 use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass};
   4 use rustc_session::{declare_lint_pass, declare_tool_lint};
   5 use syntax::ast::*;
   6
   7 declare_clippy_lint! {
   8     /// **What it does:** Checks for use of the non-existent `=*`, `=!` and `=-`
   9     /// operators.
  10     ///
  11     /// **Why is this bad?** This is either a typo of `*=`, `!=` or `-=` or
  12     /// confusing.
  13     ///
  14     /// **Known problems:** None.
  15     ///
  16     /// **Example:**
  17     /// ```rust,ignore
  18     /// a =- 42; // confusing, should it be `a -= 42` or `a = -42`?
  19     /// ```
  20     pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
  21     style,
  22     "suspicious formatting of `*=`, `-=` or `!=`"
  23 }
  24
  25 declare_clippy_lint! {
  26     /// **What it does:** Checks the formatting of a unary operator on the right hand side
  27     /// of a binary operator. It lints if there is no space between the binary and unary operators,
  28     /// but there is a space between the unary and its operand.
  29     ///
  30     /// **Why is this bad?** This is either a typo in the binary operator or confusing.
  31     ///
  32     /// **Known problems:** None.
  33     ///
  34     /// **Example:**
  35     /// ```rust,ignore
  36     /// if foo <- 30 { // this should be `foo < -30` but looks like a different operator
  37     /// }
  38     ///
  39     /// if foo &&! bar { // this should be `foo && !bar` but looks like a different operator
  40     /// }
  41     /// ```
  42     pub SUSPICIOUS_UNARY_OP_FORMATTING,
  43     style,
  44     "suspicious formatting of unary `-` or `!` on the RHS of a BinOp"
  45 }
  46
  47 declare_clippy_lint! {
  48     /// **What it does:** Checks for formatting of `else`. It lints if the `else`
  49     /// is followed immediately by a newline or the `else` seems to be missing.
  50     ///
  51     /// **Why is this bad?** This is probably some refactoring remnant, even if the
  52     /// code is correct, it might look confusing.
  53     ///
  54     /// **Known problems:** None.
  55     ///
  56     /// **Example:**
  57     /// ```rust,ignore
  58     /// if foo {
  59     /// } { // looks like an `else` is missing here
  60     /// }
  61     ///
  62     /// if foo {
  63     /// } if bar { // looks like an `else` is missing here
  64     /// }
  65     ///
  66     /// if foo {
  67     /// } else
  68     ///
  69     /// { // this is the `else` block of the previous `if`, but should it be?
  70     /// }
  71     ///
  72     /// if foo {
  73     /// } else
  74     ///
  75     /// if bar { // this is the `else` block of the previous `if`, but should it be?
  76     /// }
  77     /// ```
  78     pub SUSPICIOUS_ELSE_FORMATTING,
  79     style,
  80     "suspicious formatting of `else`"
  81 }
  82
  83 declare_clippy_lint! {
  84     /// **What it does:** Checks for possible missing comma in an array. It lints if
  85     /// an array element is a binary operator expression and it lies on two lines.
  86     ///
  87     /// **Why is this bad?** This could lead to unexpected results.
  88     ///
  89     /// **Known problems:** None.
  90     ///
  91     /// **Example:**
  92     /// ```rust,ignore
  93     /// let a = &[
  94     ///     -1, -2, -3 // <= no comma here
  95     ///     -4, -5, -6
  96     /// ];
  97     /// ```
  98     pub POSSIBLE_MISSING_COMMA,
  99     correctness,
 100     "possible missing comma in array"
 101 }
 102
 103 declare_lint_pass!(Formatting => [
 104     SUSPICIOUS_ASSIGNMENT_FORMATTING,
 105     SUSPICIOUS_UNARY_OP_FORMATTING,
 106     SUSPICIOUS_ELSE_FORMATTING,
 107     POSSIBLE_MISSING_COMMA
 108 ]);
 109
 110 impl EarlyLintPass for Formatting {
 111     fn check_block(&mut self, cx: &EarlyContext<'_>, block: &Block) {
 112         for w in block.stmts.windows(2) {
 113             match (&w[0].kind, &w[1].kind) {
 114                 (&StmtKind::Expr(ref first), &StmtKind::Expr(ref second))
 115                 | (&StmtKind::Expr(ref first), &StmtKind::Semi(ref second)) => {
 116                     check_missing_else(cx, first, second);
 117                 },
 118                 _ => (),
 119             }
 120         }
 121     }
 122
 123     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
 124         check_assign(cx, expr);
 125         check_unop(cx, expr);
 126         check_else(cx, expr);
 127         check_array(cx, expr);
 128     }
 129 }
 130
 131 /// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
 132 fn check_assign(cx: &EarlyContext<'_>, expr: &Expr) {
 133     if let ExprKind::Assign(ref lhs, ref rhs, _) = expr.kind {
 134         if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion() {
 135             let eq_span = lhs.span.between(rhs.span);
 136             if let ExprKind::Unary(op, ref sub_rhs) = rhs.kind {
 137                 if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
 138                     let op = UnOp::to_string(op);
 139                     let eqop_span = lhs.span.between(sub_rhs.span);
 140                     if eq_snippet.ends_with('=') {
 141                         span_note_and_lint(
 142                             cx,
 143                             SUSPICIOUS_ASSIGNMENT_FORMATTING,
 144                             eqop_span,
 145                             &format!(
 146                                 "this looks like you are trying to use `.. {op}= ..`, but you \
 147                                  really are doing `.. = ({op} ..)`",
 148                                 op = op
 149                             ),
 150                             eqop_span,
 151                             &format!("to remove this lint, use either `{op}=` or `= {op}`", op = op),
 152                         );
 153                     }
 154                 }
 155             }
 156         }
 157     }
 158 }
 159
 160 /// Implementation of the `SUSPICIOUS_UNARY_OP_FORMATTING` lint.
 161 fn check_unop(cx: &EarlyContext<'_>, expr: &Expr) {
 162     if_chain! {
 163         if let ExprKind::Binary(ref binop, ref lhs, ref rhs) = expr.kind;
 164         if !differing_macro_contexts(lhs.span, rhs.span) && !lhs.span.from_expansion();
 165         // span between BinOp LHS and RHS
 166         let binop_span = lhs.span.between(rhs.span);
 167         // if RHS is a UnOp
 168         if let ExprKind::Unary(op, ref un_rhs) = rhs.kind;
 169         // from UnOp operator to UnOp operand
 170         let unop_operand_span = rhs.span.until(un_rhs.span);
 171         if let Some(binop_snippet) = snippet_opt(cx, binop_span);
 172         if let Some(unop_operand_snippet) = snippet_opt(cx, unop_operand_span);
 173         let binop_str = BinOpKind::to_string(&binop.node);
 174         // no space after BinOp operator and space after UnOp operator
 175         if binop_snippet.ends_with(binop_str) && unop_operand_snippet.ends_with(' ');
 176         then {
 177             let unop_str = UnOp::to_string(op);
 178             let eqop_span = lhs.span.between(un_rhs.span);
 179             span_help_and_lint(
 180                 cx,
 181                 SUSPICIOUS_UNARY_OP_FORMATTING,
 182                 eqop_span,
 183                 &format!(
 184                     "by not having a space between `{binop}` and `{unop}` it looks like \
 185                      `{binop}{unop}` is a single operator",
 186                     binop = binop_str,
 187                     unop = unop_str
 188                 ),
 189                 &format!(
 190                     "put a space between `{binop}` and `{unop}` and remove the space after `{unop}`",
 191                     binop = binop_str,
 192                     unop = unop_str
 193                 ),
 194             );
 195         }
 196     }
 197 }
 198
 199 /// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else`.
 200 fn check_else(cx: &EarlyContext<'_>, expr: &Expr) {
 201     if_chain! {
 202         if let ExprKind::If(_, then, Some(else_)) = &expr.kind;
 203         if is_block(else_) || is_if(else_);
 204         if !differing_macro_contexts(then.span, else_.span);
 205         if !then.span.from_expansion() && !in_external_macro(cx.sess, expr.span);
 206
 207         // workaround for rust-lang/rust#43081
 208         if expr.span.lo().0 != 0 && expr.span.hi().0 != 0;
 209
 210         // this will be a span from the closing ‘}’ of the “then” block (excluding) to
 211         // the “if” of the “else if” block (excluding)
 212         let else_span = then.span.between(else_.span);
 213
 214         // the snippet should look like " else \n    " with maybe comments anywhere
 215         // it’s bad when there is a ‘\n’ after the “else”
 216         if let Some(else_snippet) = snippet_opt(cx, else_span);
 217         if let Some(else_pos) = else_snippet.find("else");
 218         if else_snippet[else_pos..].contains('\n');
 219         let else_desc = if is_if(else_) { "if" } else { "{..}" };
 220
 221         then {
 222             span_note_and_lint(
 223                 cx,
 224                 SUSPICIOUS_ELSE_FORMATTING,
 225                 else_span,
 226                 &format!("this is an `else {}` but the formatting might hide it", else_desc),
 227                 else_span,
 228                 &format!(
 229                     "to remove this lint, remove the `else` or remove the new line between \
 230                      `else` and `{}`",
 231                     else_desc,
 232                 ),
 233             );
 234         }
 235     }
 236 }
 237
 238 #[must_use]
 239 fn has_unary_equivalent(bin_op: BinOpKind) -> bool {
 240     // &, *, -
 241     bin_op == BinOpKind::And || bin_op == BinOpKind::Mul || bin_op == BinOpKind::Sub
 242 }
 243
 244 /// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
 245 fn check_array(cx: &EarlyContext<'_>, expr: &Expr) {
 246     if let ExprKind::Array(ref array) = expr.kind {
 247         for element in array {
 248             if let ExprKind::Binary(ref op, ref lhs, _) = element.kind {
 249                 if has_unary_equivalent(op.node) && !differing_macro_contexts(lhs.span, op.span) {
 250                     let space_span = lhs.span.between(op.span);
 251                     if let Some(space_snippet) = snippet_opt(cx, space_span) {
 252                         let lint_span = lhs.span.with_lo(lhs.span.hi());
 253                         if space_snippet.contains('\n') {
 254                             span_note_and_lint(
 255                                 cx,
 256                                 POSSIBLE_MISSING_COMMA,
 257                                 lint_span,
 258                                 "possibly missing a comma here",
 259                                 lint_span,
 260                                 "to remove this lint, add a comma or write the expr in a single line",
 261                             );
 262                         }
 263                     }
 264                 }
 265             }
 266         }
 267     }
 268 }
 269
 270 fn check_missing_else(cx: &EarlyContext<'_>, first: &Expr, second: &Expr) {
 271     if !differing_macro_contexts(first.span, second.span)
 272         && !first.span.from_expansion()
 273         && is_if(first)
 274         && (is_block(second) || is_if(second))
 275     {
 276         // where the else would be
 277         let else_span = first.span.between(second.span);
 278
 279         if let Some(else_snippet) = snippet_opt(cx, else_span) {
 280             if !else_snippet.contains('\n') {
 281                 let (looks_like, next_thing) = if is_if(second) {
 282                     ("an `else if`", "the second `if`")
 283                 } else {
 284                     ("an `else {..}`", "the next block")
 285                 };
 286
 287                 span_note_and_lint(
 288                     cx,
 289                     SUSPICIOUS_ELSE_FORMATTING,
 290                     else_span,
 291                     &format!("this looks like {} but the `else` is missing", looks_like),
 292                     else_span,
 293                     &format!(
 294                         "to remove this lint, add the missing `else` or add a new line before {}",
 295                         next_thing,
 296                     ),
 297                 );
 298             }
 299         }
 300     }
 301 }
 302
 303 fn is_block(expr: &Expr) -> bool {
 304     if let ExprKind::Block(..) = expr.kind {
 305         true
 306     } else {
 307         false
 308     }
 309 }
 310
 311 /// Check if the expression is an `if` or `if let`
 312 fn is_if(expr: &Expr) -> bool {
 313     if let ExprKind::If(..) = expr.kind {
 314         true
 315     } else {
 316         false
 317     }
 318 }