+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
//! Checks for if expressions that contain only an if expression.
//!
//! For example, the lint would catch:
//!
-//! ```
+//! ```rust,ignore
//! if x {
//! if y {
//! println!("Hello world");
//!
//! This lint is **warn** by default
-use rustc::lint::*;
-use std::borrow::Cow;
-use syntax::codemap::Spanned;
+use if_chain::if_chain;
+use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
+use rustc::{declare_tool_lint, lint_array};
use syntax::ast;
-use utils::{in_macro, snippet, snippet_block, span_lint_and_then};
+use crate::utils::sugg::Sugg;
+use crate::utils::{in_macro, snippet_block, snippet_block_with_applicability, span_lint_and_sugg, span_lint_and_then};
+use rustc_errors::Applicability;
-/// **What it does:** This lint checks for nested `if`-statements which can be collapsed by
-/// `&&`-combining their conditions and for `else { if .. }` expressions that can be collapsed to
-/// `else if ..`.
+/// **What it does:** Checks for nested `if` statements which can be collapsed
+/// by `&&`-combining their conditions and for `else { if ... }` expressions
+/// that
+/// can be collapsed to `else if ...`.
+///
+/// **Why is this bad?** Each `if`-statement adds one level of nesting, which
+/// makes code look more complex than it really is.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust,ignore
+/// if x {
+/// if y {
+/// …
+/// }
+/// }
///
-/// **Why is this bad?** Each `if`-statement adds one level of nesting, which makes code look more complex than it really is.
+/// // or
///
-/// **Known problems:** None
+/// if x {
+/// …
+/// } else {
+/// if y {
+/// …
+/// }
+/// }
+/// ```
///
-/// **Example:** `if x { if y { .. } }`
-declare_lint! {
+/// Should be written:
+///
+/// ```rust.ignore
+/// if x && y {
+/// …
+/// }
+///
+/// // or
+///
+/// if x {
+/// …
+/// } else if y {
+/// …
+/// }
+/// ```
+declare_clippy_lint! {
pub COLLAPSIBLE_IF,
- Warn,
- "two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` \
- can be written as `if x && y { foo() }` \
- and an `else { if .. }` expression can be collapsed to \
- `else if`"
+ style,
+ "`if`s that can be collapsed (e.g. `if x { if y { ... } }` and `else { if x { ... } }`)"
}
-#[derive(Copy,Clone)]
+#[derive(Copy, Clone)]
pub struct CollapsibleIf;
impl LintPass for CollapsibleIf {
}
impl EarlyLintPass for CollapsibleIf {
- fn check_expr(&mut self, cx: &EarlyContext, expr: &ast::Expr) {
- if !in_macro(cx, expr.span) {
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
+ if !in_macro(expr.span) {
check_if(cx, expr)
}
}
}
-fn check_if(cx: &EarlyContext, expr: &ast::Expr) {
+fn check_if(cx: &EarlyContext<'_>, expr: &ast::Expr) {
match expr.node {
ast::ExprKind::If(ref check, ref then, ref else_) => {
if let Some(ref else_) = *else_ {
} else {
check_collapsible_no_if_let(cx, expr, check, then);
}
- }
+ },
ast::ExprKind::IfLet(_, _, _, Some(ref else_)) => {
check_collapsible_maybe_if_let(cx, else_);
- }
+ },
_ => (),
}
}
-fn check_collapsible_maybe_if_let(cx: &EarlyContext, else_: &ast::Expr) {
- if_let_chain! {[
- let ast::ExprKind::Block(ref block) = else_.node,
- let Some(ref else_) = expr_block(block),
- !in_macro(cx, else_.span),
- ], {
- match else_.node {
- ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => {
- span_lint_and_then(cx,
- COLLAPSIBLE_IF,
- block.span,
- "this `else { if .. }` block can be collapsed", |db| {
- db.span_suggestion(block.span, "try", snippet_block(cx, else_.span, "..").into_owned());
- });
- }
- _ => (),
- }
- }}
+fn block_starts_with_comment(cx: &EarlyContext<'_>, expr: &ast::Block) -> bool {
+ // We trim all opening braces and whitespaces and then check if the next string is a comment.
+ let trimmed_block_text = snippet_block(cx, expr.span, "..")
+ .trim_start_matches(|c: char| c.is_whitespace() || c == '{')
+ .to_owned();
+ trimmed_block_text.starts_with("//") || trimmed_block_text.starts_with("/*")
}
-fn check_collapsible_no_if_let(
- cx: &EarlyContext,
- expr: &ast::Expr,
- check: &ast::Expr,
- then: &ast::Block,
-) {
- if_let_chain! {[
- let Some(inner) = expr_block(then),
- let ast::ExprKind::If(ref check_inner, ref content, None) = inner.node,
- ], {
- if expr.span.expn_id != inner.span.expn_id {
- return;
+fn check_collapsible_maybe_if_let(cx: &EarlyContext<'_>, else_: &ast::Expr) {
+ if_chain! {
+ if let ast::ExprKind::Block(ref block, _) = else_.node;
+ if !block_starts_with_comment(cx, block);
+ if let Some(else_) = expr_block(block);
+ if !in_macro(else_.span);
+ then {
+ match else_.node {
+ ast::ExprKind::If(..) | ast::ExprKind::IfLet(..) => {
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ COLLAPSIBLE_IF,
+ block.span,
+ "this `else { if .. }` block can be collapsed",
+ "try",
+ snippet_block_with_applicability(cx, else_.span, "..", &mut applicability).into_owned(),
+ applicability,
+ );
+ }
+ _ => (),
+ }
}
- span_lint_and_then(cx, COLLAPSIBLE_IF, expr.span, "this if statement can be collapsed", |db| {
- db.span_suggestion(expr.span,
- "try",
- format!("if {} && {} {}",
- check_to_string(cx, check),
- check_to_string(cx, check_inner),
- snippet_block(cx, content.span, "..")));
- });
- }}
-}
-
-fn requires_brackets(e: &ast::Expr) -> bool {
- match e.node {
- ast::ExprKind::Binary(Spanned { node: n, .. }, _, _) if n == ast::BinOpKind::Eq => false,
- _ => true,
}
}
-fn check_to_string(cx: &EarlyContext, e: &ast::Expr) -> Cow<'static, str> {
- if requires_brackets(e) {
- format!("({})", snippet(cx, e.span, "..")).into()
- } else {
- snippet(cx, e.span, "..")
+fn check_collapsible_no_if_let(cx: &EarlyContext<'_>, expr: &ast::Expr, check: &ast::Expr, then: &ast::Block) {
+ if_chain! {
+ if !block_starts_with_comment(cx, then);
+ if let Some(inner) = expr_block(then);
+ if let ast::ExprKind::If(ref check_inner, ref content, None) = inner.node;
+ then {
+ if expr.span.ctxt() != inner.span.ctxt() {
+ return;
+ }
+ span_lint_and_then(cx, COLLAPSIBLE_IF, expr.span, "this if statement can be collapsed", |db| {
+ let lhs = Sugg::ast(cx, check, "..");
+ let rhs = Sugg::ast(cx, check_inner, "..");
+ db.span_suggestion_with_applicability(
+ expr.span,
+ "try",
+ format!(
+ "if {} {}",
+ lhs.and(&rhs),
+ snippet_block(cx, content.span, ".."),
+ ),
+ Applicability::MachineApplicable, // snippet
+ );
+ });
+ }
}
}
-/// If the block contains only one expression, returns it.
+/// If the block contains only one expression, return it.
fn expr_block(block: &ast::Block) -> Option<&ast::Expr> {
let mut it = block.stmts.iter();
projects / rust.git / blobdiff