rust-clippy/src/misc_early.rs

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use rustc::lint::*;
use std::collections::HashMap;
use syntax::ast::*;
use syntax::codemap::Span;
use syntax::print::pprust;
use syntax::visit::FnKind;
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use utils::{span_lint, span_help_and_lint};
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/// **What it does:** This lint `Warn`s on struct field patterns bound to wildcards.
///
/// **Why is this bad?** Using `..` instead is shorter and leaves the focus on the fields that are actually bound.
///
/// **Known problems:** None.
///
/// **Example:** `let { a: _, b: ref b, c: _ } = ..`
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declare_lint!(pub UNNEEDED_FIELD_PATTERN, Warn,
"Struct fields are bound to a wildcard instead of using `..`");
/// **What it does:** This lint `Warn`s on function arguments having the same name except one starts with '_'
///
/// **Why is this bad?** It makes source code documentation more difficult
///
/// **Known problems:** None.
///
/// **Example:** `fn foo(a: i32, _a: i32) {}`
declare_lint!(pub DUPLICATE_UNDERSCORE_ARGUMENT, Warn,
"Function arguments having names which only differ by an underscore");
#[derive(Copy, Clone)]
pub struct MiscEarly;
impl LintPass for MiscEarly {
fn get_lints(&self) -> LintArray {
lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT)
}
}
impl EarlyLintPass for MiscEarly {
fn check_pat(&mut self, cx: &EarlyContext, pat: &Pat) {
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if let PatStruct(ref npat, ref pfields, _) = pat.node {
let mut wilds = 0;
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let type_name = match npat.segments.last() {
Some(elem) => format!("{}", elem.identifier.name),
None => String::new(),
};
for field in pfields {
if field.node.pat.node == PatWild {
wilds += 1;
}
}
if !pfields.is_empty() && wilds == pfields.len() {
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span_help_and_lint(cx, UNNEEDED_FIELD_PATTERN, pat.span,
"All the struct fields are matched to a wildcard pattern, \
consider using `..`.",
&format!("Try with `{} {{ .. }}` instead",
type_name));
return;
}
if wilds > 0 {
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let mut normal = vec!();
for field in pfields {
if field.node.pat.node != PatWild {
if let Ok(n) = cx.sess().codemap().span_to_snippet(field.span) {
normal.push(n);
}
}
}
for field in pfields {
if field.node.pat.node == PatWild {
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wilds -= 1;
if wilds > 0 {
span_lint(cx, UNNEEDED_FIELD_PATTERN, field.span,
"You matched a field with a wildcard pattern. \
Consider using `..` instead");
} else {
span_help_and_lint(cx, UNNEEDED_FIELD_PATTERN, field.span,
"You matched a field with a wildcard pattern. \
Consider using `..` instead",
&format!("Try with `{} {{ {}, .. }}`",
type_name,
normal[..].join(", ")));
}
}
}
}
}
}
fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, _: &Block, _: Span, _: NodeId) {
let mut registered_names : HashMap<String, Span> = HashMap::new();
for ref arg in &decl.inputs {
let arg_name = pprust::pat_to_string(&arg.pat);
if arg_name.starts_with("_") {
if let Some(correspondance) = registered_names.get(&arg_name[1..].to_owned()) {
span_lint(cx, DUPLICATE_UNDERSCORE_ARGUMENT, *correspondance,
&format!("`{}` already exists, having another argument having almost \
the same name makes code comprehension and documentation \
more difficult", arg_name[1..].to_owned()));
}
} else {
registered_names.insert(arg_name.to_owned(), arg.pat.span.clone());
}
}
}
}