7b3299e009
Instead, pretty-print the inner block and use the same style as for the "single match => if let" lint.
91 lines
2.4 KiB
Rust
91 lines
2.4 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::plugin::Registry;
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use rustc::lint::*;
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use rustc::middle::def::*;
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use syntax::ast::*;
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use syntax::ptr::P;
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use syntax::codemap::{Span, Spanned, ExpnInfo};
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use syntax::print::pprust::{block_to_string, expr_to_string};
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use utils::{in_macro, span_help_and_lint};
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declare_lint! {
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pub COLLAPSIBLE_IF,
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Warn,
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"Warn on if expressions that can be collapsed"
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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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fn check_expr(&mut self, cx: &Context, expr: &Expr) {
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cx.sess().codemap().with_expn_info(expr.span.expn_id,
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|info| check_expr_expd(cx, expr, info))
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}
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}
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fn check_expr_expd(cx: &Context, e: &Expr, info: Option<&ExpnInfo>) {
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if in_macro(cx, info) { return; }
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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), ..}) =
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single_stmt_of_block(then) {
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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(check), check_to_string(check_inner),
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block_to_string(&*content)));
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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(e: &Expr) -> String {
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if requires_brackets(e) {
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format!("({})", expr_to_string(e))
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} else {
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format!("{}", expr_to_string(e))
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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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