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Use more accurate spans for "unused delimiter" lint #88779

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Sep 11, 2021
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Use more accurate spans for "unused delimiter" lint #88779

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120 changes: 52 additions & 68 deletions compiler/rustc_lint/src/unused.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@ use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext}
use rustc_ast as ast;
use rustc_ast::util::{classify, parser};
use rustc_ast::{ExprKind, StmtKind};
use rustc_ast_pretty::pprust;
use rustc_errors::{pluralize, Applicability};
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
Expand All @@ -12,7 +11,7 @@ use rustc_middle::ty::adjustment;
use rustc_middle::ty::{self, Ty};
use rustc_span::symbol::Symbol;
use rustc_span::symbol::{kw, sym};
use rustc_span::{BytePos, Span, DUMMY_SP};
use rustc_span::{BytePos, MultiSpan, Span, DUMMY_SP};

declare_lint! {
/// The `unused_must_use` lint detects unused result of a type flagged as
Expand Down Expand Up @@ -491,77 +490,60 @@ trait UnusedDelimLint {
left_pos: Option<BytePos>,
right_pos: Option<BytePos>,
) {
let expr_text = if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
snippet
} else {
pprust::expr_to_string(value)
let spans = match value.kind {
ast::ExprKind::Block(ref block, None) if block.stmts.len() > 0 => {
let start = block.stmts[0].span;
let end = block.stmts[block.stmts.len() - 1].span;
if value.span.from_expansion() || start.from_expansion() || end.from_expansion() {
(
value.span.with_hi(value.span.lo() + BytePos(1)),
value.span.with_lo(value.span.hi() - BytePos(1)),
)
} else {
(value.span.with_hi(start.lo()), value.span.with_lo(end.hi()))
}
}
ast::ExprKind::Paren(ref expr) => {
if value.span.from_expansion() || expr.span.from_expansion() {
(
value.span.with_hi(value.span.lo() + BytePos(1)),
value.span.with_lo(value.span.hi() - BytePos(1)),
)
} else {
(value.span.with_hi(expr.span.lo()), value.span.with_lo(expr.span.hi()))
}
}
_ => return,
};
let keep_space = (
left_pos.map_or(false, |s| s >= value.span.lo()),
right_pos.map_or(false, |s| s <= value.span.hi()),
);
self.emit_unused_delims(cx, value.span, &expr_text, ctx.into(), keep_space);
self.emit_unused_delims(cx, spans, ctx.into(), keep_space);
}

fn emit_unused_delims(
&self,
cx: &EarlyContext<'_>,
span: Span,
pattern: &str,
spans: (Span, Span),
msg: &str,
keep_space: (bool, bool),
) {
// FIXME(flip1995): Quick and dirty fix for #70814. This should be fixed in rustdoc
// properly.
if span == DUMMY_SP {
if spans.0 == DUMMY_SP || spans.1 == DUMMY_SP {
return;
}

cx.struct_span_lint(self.lint(), span, |lint| {
cx.struct_span_lint(self.lint(), MultiSpan::from(vec![spans.0, spans.1]), |lint| {
let span_msg = format!("unnecessary {} around {}", Self::DELIM_STR, msg);
let mut err = lint.build(&span_msg);
let mut ate_left_paren = false;
let mut ate_right_paren = false;
let parens_removed = pattern
.trim_matches(|c| match c {
'(' | '{' => {
if ate_left_paren {
false
} else {
ate_left_paren = true;
true
}
}
')' | '}' => {
if ate_right_paren {
false
} else {
ate_right_paren = true;
true
}
}
_ => false,
})
.trim();

let replace = {
let mut replace = if keep_space.0 {
let mut s = String::from(" ");
s.push_str(parens_removed);
s
} else {
String::from(parens_removed)
};

if keep_space.1 {
replace.push(' ');
}
replace
};

let replacement = vec![
(spans.0, if keep_space.0 { " ".into() } else { "".into() }),
(spans.1, if keep_space.1 { " ".into() } else { "".into() }),
];
let suggestion = format!("remove these {}", Self::DELIM_STR);

err.span_suggestion_short(span, &suggestion, replace, Applicability::MachineApplicable);
err.multipart_suggestion(&suggestion, replacement, Applicability::MachineApplicable);
err.emit();
});
}
Expand Down Expand Up @@ -770,14 +752,15 @@ impl UnusedParens {
// Otherwise proceed with linting.
_ => {}
}

let pattern_text =
if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
snippet
} else {
pprust::pat_to_string(value)
};
self.emit_unused_delims(cx, value.span, &pattern_text, "pattern", (false, false));
let spans = if value.span.from_expansion() || inner.span.from_expansion() {
(
value.span.with_hi(value.span.lo() + BytePos(1)),
value.span.with_lo(value.span.hi() - BytePos(1)),
)
} else {
(value.span.with_hi(inner.span.lo()), value.span.with_lo(inner.span.hi()))
};
self.emit_unused_delims(cx, spans, "pattern", (false, false));
}
}
}
Expand Down Expand Up @@ -870,14 +853,15 @@ impl EarlyLintPass for UnusedParens {
);
}
_ => {
let pattern_text =
if let Ok(snippet) = cx.sess().source_map().span_to_snippet(ty.span) {
snippet
} else {
pprust::ty_to_string(ty)
};

self.emit_unused_delims(cx, ty.span, &pattern_text, "type", (false, false));
let spans = if ty.span.from_expansion() || r.span.from_expansion() {
(
ty.span.with_hi(ty.span.lo() + BytePos(1)),
ty.span.with_lo(ty.span.hi() - BytePos(1)),
)
} else {
(ty.span.with_hi(r.span.lo()), ty.span.with_lo(r.span.hi()))
};
self.emit_unused_delims(cx, spans, "type", (false, false));
}
}
}
Expand Down
7 changes: 6 additions & 1 deletion src/test/ui/async-await/issues/issue-54752-async-block.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,14 @@ warning: unnecessary parentheses around assigned value
--> $DIR/issue-54752-async-block.rs:6:22
|
LL | fn main() { let _a = (async { }); }
| ^^^^^^^^^^^^ help: remove these parentheses
| ^ ^
|
= note: `#[warn(unused_parens)]` on by default
help: remove these parentheses
|
LL - fn main() { let _a = (async { }); }
LL + fn main() { let _a = async { }; }
|

warning: 1 warning emitted

7 changes: 6 additions & 1 deletion src/test/ui/const-generics/unused_braces.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,13 +2,18 @@ warning: unnecessary braces around const expression
--> $DIR/unused_braces.rs:9:14
|
LL | let _: A<{ 7 }>;
| ^^^^^ help: remove these braces
| ^^ ^^
|
note: the lint level is defined here
--> $DIR/unused_braces.rs:3:9
|
LL | #![warn(unused_braces)]
| ^^^^^^^^^^^^^
help: remove these braces
|
LL - let _: A<{ 7 }>;
LL + let _: A<7>;
|

warning: 1 warning emitted

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