Make `used_underscore_binding` lint compatible with MacroAttributes
expansions. TODO: Add a good test for this.
This commit is contained in:
Devon Hollowood 2015-12-21 01:03:12 -08:00
parent 4a32445aa7
commit b190aa7deb
2 changed files with 31 additions and 7 deletions

View file

@ -3,7 +3,7 @@ use syntax::ptr::P;
use rustc_front::hir::*;
use reexport::*;
use rustc_front::util::{is_comparison_binop, binop_to_string};
use syntax::codemap::{Span, Spanned};
use syntax::codemap::{Span, Spanned, ExpnFormat};
use rustc_front::intravisit::FnKind;
use rustc::middle::ty;
use rustc::middle::const_eval::ConstVal::Float;
@ -11,7 +11,7 @@ use rustc::middle::const_eval::eval_const_expr_partial;
use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
use utils::{get_item_name, match_path, snippet, get_parent_expr, span_lint};
use utils::{span_help_and_lint, in_external_macro, walk_ptrs_ty, is_integer_literal};
use utils::{span_help_and_lint, walk_ptrs_ty, is_integer_literal};
/// **What it does:** This lint checks for function arguments and let bindings denoted as `ref`. It is `Warn` by default.
///
@ -345,6 +345,9 @@ impl LintPass for UsedUnderscoreBinding {
impl LateLintPass for UsedUnderscoreBinding {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if in_attributes_expansion(cx, expr) { // Don't lint things expanded by #[derive(...)], etc
return;
}
let needs_lint = match expr.node {
ExprPath(_, ref path) => {
let ident = path.segments.last()
@ -352,7 +355,7 @@ impl LateLintPass for UsedUnderscoreBinding {
.identifier;
ident.name.as_str().chars().next() == Some('_') //starts with '_'
&& ident.name.as_str().chars().skip(1).next() != Some('_') //doesn't start with "__"
&& ident.name != ident.unhygienic_name //not in macro
&& ident.name != ident.unhygienic_name //not in bang macro
&& is_used(cx, expr)
},
ExprField(_, spanned) => {
@ -362,9 +365,6 @@ impl LateLintPass for UsedUnderscoreBinding {
},
_ => false
};
if in_external_macro(cx, expr.span) {
return
}
if needs_lint {
cx.span_lint(USED_UNDERSCORE_BINDING, expr.span,
"used binding which is prefixed with an underscore. A leading underscore \
@ -373,6 +373,8 @@ impl LateLintPass for UsedUnderscoreBinding {
}
}
/// Heuristic to see if an expression is used. Should be compatible with `unused_variables`'s idea
/// of what it means for an expression to be "used".
fn is_used(cx: &LateContext, expr: &Expr) -> bool {
if let Some(ref parent) = get_parent_expr(cx, expr) {
match parent.node {
@ -385,3 +387,16 @@ fn is_used(cx: &LateContext, expr: &Expr) -> bool {
true
}
}
/// Test whether an expression is in a macro expansion (e.g. something generated by #[derive(...)]
/// or the like)
fn in_attributes_expansion(cx: &LateContext, expr: &Expr) -> bool {
cx.sess().codemap().with_expn_info(expr.span.expn_id, |info_opt| {
info_opt.map_or(false, |info| {
match info.callee.format {
ExpnFormat::MacroAttribute(_) => true,
_ => false,
}
})
})
}

View file

@ -9,7 +9,15 @@ fn prefix_underscore(_foo: u32) -> u32 {
/// Test that we lint even if the use is within a macro expansion
fn in_macro(_foo: u32) {
println!("{}", _foo); // doesn't warn, nut should #507
println!("{}", _foo); //~ ERROR used binding which is prefixed with an underscore
}
// TODO: This doesn't actually correctly test this. Need to find a #[derive(...)] which sets off
// the lint if the `in_attributes_expansion` test isn't there
/// Test that we do not lint for unused underscores in a MacroAttribute expansion
#[derive(Clone)]
struct MacroAttributesTest {
_foo: u32,
}
// Struct for testing use of fields prefixed with an underscore
@ -68,6 +76,7 @@ fn non_variables() {
fn main() {
let foo = 0u32;
let _ = MacroAttributesTest{_foo: 0};
// tests of unused_underscore lint
let _ = prefix_underscore(foo);
in_macro(foo);