use rustc::lint::*;
use syntax::ast;
use syntax_pos::{Span, NO_EXPANSION};
use utils::{differing_macro_contexts, in_macro, snippet_opt, span_note_and_lint};
use syntax::ptr::P;
/// **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`?
/// ```
declare_lint! {
pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
Warn,
"suspicious formatting of `*=`, `-=` or `!=`"
}
/// **What it does:** Checks for formatting of `else if`. It lints if the `else`
/// and `if` are not on the same line 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 {
/// } if bar { // looks like an `else` is missing here
/// }
///
/// if foo {
/// } else
///
/// if bar { // this is the `else` block of the previous `if`, but should it be?
/// }
/// ```
declare_lint! {
pub SUSPICIOUS_ELSE_FORMATTING,
Warn,
"suspicious formatting of `else if`"
}
/// **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
/// ];
/// ```
declare_lint! {
pub POSSIBLE_MISSING_COMMA,
Warn,
"possible missing comma in array"
}
#[derive(Copy,Clone)]
pub struct Formatting;
impl LintPass for Formatting {
fn get_lints(&self) -> LintArray {
lint_array![SUSPICIOUS_ASSIGNMENT_FORMATTING, SUSPICIOUS_ELSE_FORMATTING, POSSIBLE_MISSING_COMMA]
}
}
impl EarlyLintPass for Formatting {
fn check_block(&mut self, cx: &EarlyContext, block: &ast::Block) {
for w in block.stmts.windows(2) {
match (&w[0].node, &w[1].node) {
(&ast::StmtKind::Expr(ref first), &ast::StmtKind::Expr(ref second)) |
(&ast::StmtKind::Expr(ref first), &ast::StmtKind::Semi(ref second)) => {
check_consecutive_ifs(cx, first, second);
},
_ => (),
}
}
}
fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
check_assign(cx, expr);
check_else_if(cx, expr);
check_array(cx, expr);
}
}
/// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
fn check_assign(cx: &EarlyContext, expr: &ast::Expr) {
if let ast::ExprKind::Assign(ref lhs, ref rhs) = expr.node {
if !differing_macro_contexts(lhs.span, rhs.span) && !in_macro(lhs.span) {
let eq_span = Span {
lo: lhs.span.hi,
hi: rhs.span.lo,
ctxt: NO_EXPANSION,
};
if let ast::ExprKind::Unary(op, ref sub_rhs) = rhs.node {
if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
let op = ast::UnOp::to_string(op);
let eqop_span = Span {
lo: lhs.span.hi,
hi: sub_rhs.span.lo,
ctxt: NO_EXPANSION,
};
if eq_snippet.ends_with('=') {
span_note_and_lint(cx,
SUSPICIOUS_ASSIGNMENT_FORMATTING,
eqop_span,
&format!("this looks like you are trying to use `.. {op}= ..`, but you \
really are doing `.. = ({op} ..)`",
op = op),
eqop_span,
&format!("to remove this lint, use either `{op}=` or `= {op}`", op = op));
}
}
}
}
}
}
/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else if`.
fn check_else_if(cx: &EarlyContext, expr: &ast::Expr) {
if let Some((then, &Some(ref else_))) = unsugar_if(expr) {
if unsugar_if(else_).is_some() && !differing_macro_contexts(then.span, else_.span) && !in_macro(then.span) {
// this will be a span from the closing ‘}’ of the “then” block (excluding) to the
// “if” of the “else if” block (excluding)
let else_span = Span {
lo: then.span.hi,
hi: else_.span.lo,
ctxt: NO_EXPANSION,
};
// the snippet should look like " else \n " with maybe comments anywhere
// it’s bad when there is a ‘\n’ after the “else”
if let Some(else_snippet) = snippet_opt(cx, else_span) {
let else_pos = else_snippet.find("else").expect("there must be a `else` here");
if else_snippet[else_pos..].contains('\n') {
span_note_and_lint(cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
"this is an `else if` but the formatting might hide it",
else_span,
"to remove this lint, remove the `else` or remove the new line between `else` \
and `if`");
}
}
}
}
}
/// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
fn check_array(cx: &EarlyContext, expr: &ast::Expr) {
if let ast::ExprKind::Array(ref array) = expr.node {
for element in array {
if let ast::ExprKind::Binary(ref op, ref lhs, _) = element.node {
if !differing_macro_contexts(lhs.span, op.span) {
let space_span = Span {
lo: lhs.span.hi,
hi: op.span.lo,
ctxt: NO_EXPANSION,
};
if let Some(space_snippet) = snippet_opt(cx, space_span) {
let lint_span = Span {
lo: lhs.span.hi,
hi: lhs.span.hi,
ctxt: NO_EXPANSION,
};
if space_snippet.contains('\n') {
span_note_and_lint(cx,
POSSIBLE_MISSING_COMMA,
lint_span,
"possibly missing a comma here",
lint_span,
"to remove this lint, add a comma or write the expr in a single line");
}
}
}
}
}
}
}
/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for consecutive ifs.
fn check_consecutive_ifs(cx: &EarlyContext, first: &ast::Expr, second: &ast::Expr) {
if !differing_macro_contexts(first.span, second.span) && !in_macro(first.span) && unsugar_if(first).is_some() &&
unsugar_if(second).is_some() {
// where the else would be
let else_span = Span {
lo: first.span.hi,
hi: second.span.lo,
ctxt: NO_EXPANSION,
};
if let Some(else_snippet) = snippet_opt(cx, else_span) {
if !else_snippet.contains('\n') {
span_note_and_lint(cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
"this looks like an `else if` but the `else` is missing",
else_span,
"to remove this lint, add the missing `else` or add a new line before the second \
`if`");
}
}
}
}
/// Match `if` or `if let` expressions and return the `then` and `else` block.
fn unsugar_if(expr: &ast::Expr) -> Option<(&P<ast::Block>, &Option<P<ast::Expr>>)> {
match expr.node {
ast::ExprKind::If(_, ref then, ref else_) |
ast::ExprKind::IfLet(_, _, ref then, ref else_) => Some((then, else_)),
_ => None,
}
}