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Auto merge of #7707 - Jarcho:suspicious_else_proc_mac, r=Manishearth
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Don't lint `suspicious_else_formatting` inside proc-macros

fixes: #7650

I'll add a test for this one soon.

changelog: Don't lint `suspicious_else_formatting` inside proc-macros
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@bors
bors committed Sep 23, 2021
2 parents ef2e2f0 + e69154f commit cd3f3cf
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Showing 4 changed files with 124 additions and 35 deletions.
57 changes: 31 additions & 26 deletions clippy_lints/src/formatting.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -286,34 +286,39 @@ fn check_array(cx: &EarlyContext<'_>, expr: &Expr) {
}

fn check_missing_else(cx: &EarlyContext<'_>, first: &Expr, second: &Expr) {
if !differing_macro_contexts(first.span, second.span)
&& !first.span.from_expansion()
&& is_if(first)
&& (is_block(second) || is_if(second))
{
// where the else would be
let else_span = first.span.between(second.span);
if_chain! {
if !differing_macro_contexts(first.span, second.span);
if !first.span.from_expansion();
if let ExprKind::If(cond_expr, ..) = &first.kind;
if is_block(second) || is_if(second);

if let Some(else_snippet) = snippet_opt(cx, else_span) {
if !else_snippet.contains('\n') {
let (looks_like, next_thing) = if is_if(second) {
("an `else if`", "the second `if`")
} else {
("an `else {..}`", "the next block")
};
// Proc-macros can give weird spans. Make sure this is actually an `if`.
if let Some(if_snip) = snippet_opt(cx, first.span.until(cond_expr.span));
if if_snip.starts_with("if");

span_lint_and_note(
cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
&format!("this looks like {} but the `else` is missing", looks_like),
None,
&format!(
"to remove this lint, add the missing `else` or add a new line before {}",
next_thing,
),
);
}
// If there is a line break between the two expressions, don't lint.
// If there is a non-whitespace character, this span came from a proc-macro.
let else_span = first.span.between(second.span);
if let Some(else_snippet) = snippet_opt(cx, else_span);
if !else_snippet.chars().any(|c| c == '\n' || !c.is_whitespace());
then {
let (looks_like, next_thing) = if is_if(second) {
("an `else if`", "the second `if`")
} else {
("an `else {..}`", "the next block")
};

span_lint_and_note(
cx,
SUSPICIOUS_ELSE_FORMATTING,
else_span,
&format!("this looks like {} but the `else` is missing", looks_like),
None,
&format!(
"to remove this lint, add the missing `else` or add a new line before {}",
next_thing,
),
);
}
}
}
Expand Down
75 changes: 75 additions & 0 deletions tests/ui/auxiliary/proc_macro_suspicious_else_formatting.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,75 @@
// compile-flags: --emit=link
// no-prefer-dynamic

#![crate_type = "proc-macro"]

extern crate proc_macro;
use proc_macro::{token_stream, Delimiter, Group, Ident, Span, TokenStream, TokenTree};
use std::iter::FromIterator;

fn read_ident(iter: &mut token_stream::IntoIter) -> Ident {
match iter.next() {
Some(TokenTree::Ident(i)) => i,
_ => panic!("expected ident"),
}
}

#[proc_macro_derive(DeriveBadSpan)]
pub fn derive_bad_span(input: TokenStream) -> TokenStream {
let mut input = input.into_iter();
assert_eq!(read_ident(&mut input).to_string(), "struct");
let ident = read_ident(&mut input);
let mut tys = match input.next() {
Some(TokenTree::Group(g)) if g.delimiter() == Delimiter::Parenthesis => g.stream().into_iter(),
_ => panic!(),
};
let field1 = read_ident(&mut tys);
tys.next();
let field2 = read_ident(&mut tys);

<TokenStream as FromIterator<TokenTree>>::from_iter(
[
Ident::new("impl", Span::call_site()).into(),
ident.into(),
Group::new(
Delimiter::Brace,
<TokenStream as FromIterator<TokenTree>>::from_iter(
[
Ident::new("fn", Span::call_site()).into(),
Ident::new("_foo", Span::call_site()).into(),
Group::new(Delimiter::Parenthesis, TokenStream::new()).into(),
Group::new(
Delimiter::Brace,
<TokenStream as FromIterator<TokenTree>>::from_iter(
[
Ident::new("if", field1.span()).into(),
Ident::new("true", field1.span()).into(),
{
let mut group = Group::new(Delimiter::Brace, TokenStream::new());
group.set_span(field1.span());
group.into()
},
Ident::new("if", field2.span()).into(),
Ident::new("true", field2.span()).into(),
{
let mut group = Group::new(Delimiter::Brace, TokenStream::new());
group.set_span(field2.span());
group.into()
},
]
.iter()
.cloned(),
),
)
.into(),
]
.iter()
.cloned(),
),
)
.into(),
]
.iter()
.cloned(),
)
}
9 changes: 9 additions & 0 deletions tests/ui/suspicious_else_formatting.rs
View file
Original file line number Diff line number Diff line change
@@ -1,5 +1,10 @@
// aux-build:proc_macro_suspicious_else_formatting.rs

#![warn(clippy::suspicious_else_formatting)]

extern crate proc_macro_suspicious_else_formatting;
use proc_macro_suspicious_else_formatting::DeriveBadSpan;

fn foo() -> bool {
true
}
Expand Down Expand Up @@ -103,3 +108,7 @@ fn main() {
{
}
}

// #7650 - Don't lint. Proc-macro using bad spans for `if` expressions.
#[derive(DeriveBadSpan)]
struct _Foo(u32, u32);
18 changes: 9 additions & 9 deletions tests/ui/suspicious_else_formatting.stderr
View file
Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
error: this looks like an `else {..}` but the `else` is missing
--> $DIR/suspicious_else_formatting.rs:11:6
--> $DIR/suspicious_else_formatting.rs:16:6
|
LL | } {
| ^
Expand All @@ -8,31 +8,31 @@ LL | } {
= note: to remove this lint, add the missing `else` or add a new line before the next block

error: this looks like an `else if` but the `else` is missing
--> $DIR/suspicious_else_formatting.rs:15:6
--> $DIR/suspicious_else_formatting.rs:20:6
|
LL | } if foo() {
| ^
|
= note: to remove this lint, add the missing `else` or add a new line before the second `if`

error: this looks like an `else if` but the `else` is missing
--> $DIR/suspicious_else_formatting.rs:22:10
--> $DIR/suspicious_else_formatting.rs:27:10
|
LL | } if foo() {
| ^
|
= note: to remove this lint, add the missing `else` or add a new line before the second `if`

error: this looks like an `else if` but the `else` is missing
--> $DIR/suspicious_else_formatting.rs:30:10
--> $DIR/suspicious_else_formatting.rs:35:10
|
LL | } if foo() {
| ^
|
= note: to remove this lint, add the missing `else` or add a new line before the second `if`

error: this is an `else {..}` but the formatting might hide it
--> $DIR/suspicious_else_formatting.rs:39:6
--> $DIR/suspicious_else_formatting.rs:44:6
|
LL | } else
| ______^
Expand All @@ -42,7 +42,7 @@ LL | | {
= note: to remove this lint, remove the `else` or remove the new line between `else` and `{..}`

error: this is an `else if` but the formatting might hide it
--> $DIR/suspicious_else_formatting.rs:51:6
--> $DIR/suspicious_else_formatting.rs:56:6
|
LL | } else
| ______^
Expand All @@ -52,7 +52,7 @@ LL | | if foo() { // the span of the above error should continue here
= note: to remove this lint, remove the `else` or remove the new line between `else` and `if`

error: this is an `else if` but the formatting might hide it
--> $DIR/suspicious_else_formatting.rs:56:6
--> $DIR/suspicious_else_formatting.rs:61:6
|
LL | }
| ______^
Expand All @@ -63,7 +63,7 @@ LL | | if foo() { // the span of the above error should continue here
= note: to remove this lint, remove the `else` or remove the new line between `else` and `if`

error: this is an `else {..}` but the formatting might hide it
--> $DIR/suspicious_else_formatting.rs:83:6
--> $DIR/suspicious_else_formatting.rs:88:6
|
LL | }
| ______^
Expand All @@ -75,7 +75,7 @@ LL | | {
= note: to remove this lint, remove the `else` or remove the new line between `else` and `{..}`

error: this is an `else {..}` but the formatting might hide it
--> $DIR/suspicious_else_formatting.rs:91:6
--> $DIR/suspicious_else_formatting.rs:96:6
|
LL | }
| ______^
Expand Down

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