93 lines
2.5 KiB
Rust
93 lines
2.5 KiB
Rust
//! Checks for if expressions that contain only an if expression.
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//!
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//! For example, the lint would catch:
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//!
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//! ```
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//! if x {
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//! if y {
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//! println!("Hello world");
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//! }
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//! }
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//! ```
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//!
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//! This lint is **warn** by default
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use rustc::lint::*;
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use rustc_front::hir::*;
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use syntax::codemap::Spanned;
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use utils::{in_macro, span_help_and_lint, snippet, snippet_block};
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declare_lint! {
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pub COLLAPSIBLE_IF,
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Warn,
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"two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` \
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can be written as `if x && y { foo() }`"
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}
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#[derive(Copy,Clone)]
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pub struct CollapsibleIf;
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impl LintPass for CollapsibleIf {
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fn get_lints(&self) -> LintArray {
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lint_array!(COLLAPSIBLE_IF)
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}
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}
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impl LateLintPass for CollapsibleIf {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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if !in_macro(cx, expr.span) {
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check_if(cx, expr)
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}
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}
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}
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fn check_if(cx: &LateContext, e: &Expr) {
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if let ExprIf(ref check, ref then, None) = e.node {
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if let Some(&Expr{ node: ExprIf(ref check_inner, ref content, None), span: sp, ..}) =
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single_stmt_of_block(then) {
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if e.span.expn_id != sp.expn_id {
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return;
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}
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span_help_and_lint(cx, COLLAPSIBLE_IF, e.span,
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"this if statement can be collapsed",
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&format!("try\nif {} && {} {}",
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check_to_string(cx, check), check_to_string(cx, check_inner),
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snippet_block(cx, content.span, "..")));
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}
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}
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}
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fn requires_brackets(e: &Expr) -> bool {
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match e.node {
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ExprBinary(Spanned {node: n, ..}, _, _) if n == BiEq => false,
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_ => true
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}
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}
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fn check_to_string(cx: &LateContext, e: &Expr) -> String {
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if requires_brackets(e) {
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format!("({})", snippet(cx, e.span, ".."))
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} else {
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format!("{}", snippet(cx, e.span, ".."))
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}
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}
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fn single_stmt_of_block(block: &Block) -> Option<&Expr> {
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if block.stmts.len() == 1 && block.expr.is_none() {
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if let StmtExpr(ref expr, _) = block.stmts[0].node {
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single_stmt_of_expr(expr)
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} else { None }
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} else {
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if block.stmts.is_empty() {
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if let Some(ref p) = block.expr { Some(p) } else { None }
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} else { None }
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}
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}
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fn single_stmt_of_expr(expr: &Expr) -> Option<&Expr> {
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if let ExprBlock(ref block) = expr.node {
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single_stmt_of_block(block)
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} else { Some(expr) }
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}
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