224 lines
7.8 KiB
Rust
224 lines
7.8 KiB
Rust
use rustc::lint::*;
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use syntax::ast;
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use utils::{differing_macro_contexts, in_macro, snippet_opt, span_note_and_lint};
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use syntax::ptr::P;
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/// **What it does:** Checks for use of the non-existent `=*`, `=!` and `=-`
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/// operators.
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///
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/// **Why is this bad?** This is either a typo of `*=`, `!=` or `-=` or
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/// confusing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// a =- 42; // confusing, should it be `a -= 42` or `a = -42`?
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/// ```
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declare_lint! {
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pub SUSPICIOUS_ASSIGNMENT_FORMATTING,
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Warn,
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"suspicious formatting of `*=`, `-=` or `!=`"
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}
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/// **What it does:** Checks for formatting of `else if`. It lints if the `else`
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/// and `if` are not on the same line or the `else` seems to be missing.
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///
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/// **Why is this bad?** This is probably some refactoring remnant, even if the
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/// code is correct, it might look confusing.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// if foo {
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/// } if bar { // looks like an `else` is missing here
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/// }
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///
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/// if foo {
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/// } else
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///
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/// if bar { // this is the `else` block of the previous `if`, but should it be?
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/// }
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/// ```
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declare_lint! {
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pub SUSPICIOUS_ELSE_FORMATTING,
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Warn,
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"suspicious formatting of `else if`"
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}
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/// **What it does:** Checks for possible missing comma in an array. It lints if
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/// an array element is a binary operator expression and it lies on two lines.
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///
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/// **Why is this bad?** This could lead to unexpected results.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// let a = &[
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/// -1, -2, -3 // <= no comma here
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/// -4, -5, -6
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/// ];
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/// ```
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declare_lint! {
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pub POSSIBLE_MISSING_COMMA,
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Warn,
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"possible missing comma in array"
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}
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#[derive(Copy, Clone)]
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pub struct Formatting;
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impl LintPass for Formatting {
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fn get_lints(&self) -> LintArray {
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lint_array!(
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SUSPICIOUS_ASSIGNMENT_FORMATTING,
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SUSPICIOUS_ELSE_FORMATTING,
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POSSIBLE_MISSING_COMMA
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)
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}
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}
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impl EarlyLintPass for Formatting {
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fn check_block(&mut self, cx: &EarlyContext, block: &ast::Block) {
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for w in block.stmts.windows(2) {
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match (&w[0].node, &w[1].node) {
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(&ast::StmtKind::Expr(ref first), &ast::StmtKind::Expr(ref second)) |
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(&ast::StmtKind::Expr(ref first), &ast::StmtKind::Semi(ref second)) => {
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check_consecutive_ifs(cx, first, second);
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},
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_ => (),
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}
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}
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}
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fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
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check_assign(cx, expr);
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check_else_if(cx, expr);
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check_array(cx, expr);
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}
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}
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/// Implementation of the `SUSPICIOUS_ASSIGNMENT_FORMATTING` lint.
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fn check_assign(cx: &EarlyContext, expr: &ast::Expr) {
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if let ast::ExprKind::Assign(ref lhs, ref rhs) = expr.node {
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if !differing_macro_contexts(lhs.span, rhs.span) && !in_macro(lhs.span) {
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let eq_span = lhs.span.between(rhs.span);
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if let ast::ExprKind::Unary(op, ref sub_rhs) = rhs.node {
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if let Some(eq_snippet) = snippet_opt(cx, eq_span) {
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let op = ast::UnOp::to_string(op);
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let eqop_span = lhs.span.between(sub_rhs.span);
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if eq_snippet.ends_with('=') {
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span_note_and_lint(
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cx,
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SUSPICIOUS_ASSIGNMENT_FORMATTING,
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eqop_span,
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&format!(
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"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
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),
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eqop_span,
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&format!("to remove this lint, use either `{op}=` or `= {op}`", op = op),
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);
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}
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}
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}
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}
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}
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}
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/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for weird `else if`.
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fn check_else_if(cx: &EarlyContext, expr: &ast::Expr) {
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if let Some((then, &Some(ref else_))) = unsugar_if(expr) {
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if unsugar_if(else_).is_some() && !differing_macro_contexts(then.span, else_.span) && !in_macro(then.span) {
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// this will be a span from the closing ‘}’ of the “then” block (excluding) to
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// the
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// “if” of the “else if” block (excluding)
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let else_span = then.span.between(else_.span);
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// the snippet should look like " else \n " with maybe comments anywhere
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// it’s bad when there is a ‘\n’ after the “else”
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if let Some(else_snippet) = snippet_opt(cx, else_span) {
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let else_pos = else_snippet
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.find("else")
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.expect("there must be a `else` here");
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if else_snippet[else_pos..].contains('\n') {
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span_note_and_lint(
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cx,
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SUSPICIOUS_ELSE_FORMATTING,
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else_span,
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"this is an `else if` but the formatting might hide it",
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else_span,
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"to remove this lint, remove the `else` or remove the new line between `else` \
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and `if`",
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);
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}
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}
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}
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}
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}
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/// Implementation of the `POSSIBLE_MISSING_COMMA` lint for array
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fn check_array(cx: &EarlyContext, expr: &ast::Expr) {
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if let ast::ExprKind::Array(ref array) = expr.node {
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for element in array {
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if let ast::ExprKind::Binary(ref op, ref lhs, _) = element.node {
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if !differing_macro_contexts(lhs.span, op.span) {
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let space_span = lhs.span.between(op.span);
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if let Some(space_snippet) = snippet_opt(cx, space_span) {
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let lint_span = lhs.span.with_lo(lhs.span.hi());
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if space_snippet.contains('\n') {
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span_note_and_lint(
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cx,
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POSSIBLE_MISSING_COMMA,
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lint_span,
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"possibly missing a comma here",
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lint_span,
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"to remove this lint, add a comma or write the expr in a single line",
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);
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}
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}
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}
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}
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}
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}
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}
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/// Implementation of the `SUSPICIOUS_ELSE_FORMATTING` lint for consecutive ifs.
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fn check_consecutive_ifs(cx: &EarlyContext, first: &ast::Expr, second: &ast::Expr) {
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if !differing_macro_contexts(first.span, second.span) && !in_macro(first.span) && unsugar_if(first).is_some()
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&& unsugar_if(second).is_some()
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{
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// where the else would be
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let else_span = first.span.between(second.span);
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if let Some(else_snippet) = snippet_opt(cx, else_span) {
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if !else_snippet.contains('\n') {
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span_note_and_lint(
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cx,
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SUSPICIOUS_ELSE_FORMATTING,
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else_span,
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"this looks like an `else if` but the `else` is missing",
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else_span,
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"to remove this lint, add the missing `else` or add a new line before the second \
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`if`",
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);
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}
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}
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}
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}
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/// Match `if` or `if let` expressions and return the `then` and `else` block.
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fn unsugar_if(expr: &ast::Expr) -> Option<(&P<ast::Block>, &Option<P<ast::Expr>>)> {
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match expr.node {
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ast::ExprKind::If(_, ref then, ref else_) | ast::ExprKind::IfLet(_, _, ref then, ref else_) => {
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Some((then, else_))
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},
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_ => None,
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}
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}
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