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https://github.com/rust-lang/rust-clippy
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Implement #507
Make `used_underscore_binding` lint compatible with MacroAttributes expansions. TODO: Add a good test for this.
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parent
4a32445aa7
commit
b190aa7deb
2 changed files with 31 additions and 7 deletions
27
src/misc.rs
27
src/misc.rs
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@ -3,7 +3,7 @@ use syntax::ptr::P;
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use rustc_front::hir::*;
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use reexport::*;
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use rustc_front::util::{is_comparison_binop, binop_to_string};
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use syntax::codemap::{Span, Spanned};
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use syntax::codemap::{Span, Spanned, ExpnFormat};
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use rustc_front::intravisit::FnKind;
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use rustc::middle::ty;
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use rustc::middle::const_eval::ConstVal::Float;
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@ -11,7 +11,7 @@ use rustc::middle::const_eval::eval_const_expr_partial;
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use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
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use utils::{get_item_name, match_path, snippet, get_parent_expr, span_lint};
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use utils::{span_help_and_lint, in_external_macro, walk_ptrs_ty, is_integer_literal};
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use utils::{span_help_and_lint, walk_ptrs_ty, is_integer_literal};
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/// **What it does:** This lint checks for function arguments and let bindings denoted as `ref`. It is `Warn` by default.
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///
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@ -345,6 +345,9 @@ impl LintPass for UsedUnderscoreBinding {
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impl LateLintPass for UsedUnderscoreBinding {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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if in_attributes_expansion(cx, expr) { // Don't lint things expanded by #[derive(...)], etc
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return;
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}
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let needs_lint = match expr.node {
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ExprPath(_, ref path) => {
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let ident = path.segments.last()
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@ -352,7 +355,7 @@ impl LateLintPass for UsedUnderscoreBinding {
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.identifier;
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ident.name.as_str().chars().next() == Some('_') //starts with '_'
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&& ident.name.as_str().chars().skip(1).next() != Some('_') //doesn't start with "__"
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&& ident.name != ident.unhygienic_name //not in macro
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&& ident.name != ident.unhygienic_name //not in bang macro
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&& is_used(cx, expr)
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},
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ExprField(_, spanned) => {
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@ -362,9 +365,6 @@ impl LateLintPass for UsedUnderscoreBinding {
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},
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_ => false
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};
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if in_external_macro(cx, expr.span) {
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return
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}
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if needs_lint {
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cx.span_lint(USED_UNDERSCORE_BINDING, expr.span,
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"used binding which is prefixed with an underscore. A leading underscore \
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@ -373,6 +373,8 @@ impl LateLintPass for UsedUnderscoreBinding {
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}
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}
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/// Heuristic to see if an expression is used. Should be compatible with `unused_variables`'s idea
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/// of what it means for an expression to be "used".
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fn is_used(cx: &LateContext, expr: &Expr) -> bool {
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if let Some(ref parent) = get_parent_expr(cx, expr) {
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match parent.node {
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@ -385,3 +387,16 @@ fn is_used(cx: &LateContext, expr: &Expr) -> bool {
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true
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}
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}
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/// Test whether an expression is in a macro expansion (e.g. something generated by #[derive(...)]
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/// or the like)
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fn in_attributes_expansion(cx: &LateContext, expr: &Expr) -> bool {
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cx.sess().codemap().with_expn_info(expr.span.expn_id, |info_opt| {
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info_opt.map_or(false, |info| {
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match info.callee.format {
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ExpnFormat::MacroAttribute(_) => true,
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_ => false,
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}
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})
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})
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}
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@ -9,7 +9,15 @@ fn prefix_underscore(_foo: u32) -> u32 {
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/// Test that we lint even if the use is within a macro expansion
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fn in_macro(_foo: u32) {
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println!("{}", _foo); // doesn't warn, nut should #507
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println!("{}", _foo); //~ ERROR used binding which is prefixed with an underscore
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}
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// TODO: This doesn't actually correctly test this. Need to find a #[derive(...)] which sets off
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// the lint if the `in_attributes_expansion` test isn't there
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/// Test that we do not lint for unused underscores in a MacroAttribute expansion
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#[derive(Clone)]
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struct MacroAttributesTest {
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_foo: u32,
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}
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// Struct for testing use of fields prefixed with an underscore
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@ -68,6 +76,7 @@ fn non_variables() {
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fn main() {
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let foo = 0u32;
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let _ = MacroAttributesTest{_foo: 0};
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// tests of unused_underscore lint
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let _ = prefix_underscore(foo);
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in_macro(foo);
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