41 lines
1.2 KiB
Rust
41 lines
1.2 KiB
Rust
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use rustc::lint::*;
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use rustc_front::hir::*;
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use utils::{is_expn_of, span_lint};
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/// **What it does:** This lints about use of `format!("string literal with no argument")`.
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///
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/// **Why is this bad?** There is no point of doing that. If you want a `String` you can use
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/// `to_owned` on the string literal. The even worst `&format!("foo")` is often encountered in the
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/// wild.
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///
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/// **Known problems:** None.
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///
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/// **Example:** `format!("foo")`
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declare_lint! {
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pub USELESS_FORMAT,
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Warn,
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"useless use of `format!`"
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}
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#[derive(Copy, Clone, Debug)]
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pub struct FormatMacLint;
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impl LintPass for FormatMacLint {
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fn get_lints(&self) -> LintArray {
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lint_array![USELESS_FORMAT]
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}
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}
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impl LateLintPass for FormatMacLint {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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// `format!("foo")` expansion contains `match () { () => [], }`
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if let ExprMatch(ref matchee, _, _) = expr.node {
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if let ExprTup(ref tup) = matchee.node {
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if tup.is_empty() && is_expn_of(cx, expr.span, "format").is_some() {
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span_lint(cx, USELESS_FORMAT, expr.span, &"useless use of `format!`");
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}
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}
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}
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}
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}
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