mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Handle attempts to have multiple cfgd tail expressions

Browse Source 
When encountering code that seems like it might be trying to have
multiple tail expressions depending on `cfg` information, suggest
alternatives that will success to parse.

```rust
fn foo() -> String {
    #[cfg(feature = "validation")]
    [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
    #[cfg(not(feature = "validation"))]
    String::new()
}
```

```
error: expected `;`, found `#`
  --> $DIR/multiple-tail-expr-behind-cfg.rs:5:64
   |
LL |     #[cfg(feature = "validation")]
   |     ------------------------------ only `;` terminated statements or tail expressions are allowed after this attribute
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
   |                                                                ^ expected `;` here
LL |     #[cfg(not(feature = "validation"))]
   |     - unexpected token
   |
help: add `;` here
   |
LL |     [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
   |                                                                +
help: alternatively, consider surrounding the expression with a block
   |
LL |     { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
   |     +                                                             +
help: it seems like you are trying to provide different expressions depending on `cfg`, consider using `if cfg!(..)`
   |
LL ~     if cfg!(feature = "validation") {
LL ~         [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
LL ~     } else if cfg!(not(feature = "validation")) {
LL ~         String::new()
LL +     }
   |
```

Fix #106020.
This commit is contained in:
Esteban Küber 2023-11-16 21:21:26 +00:00
parent 1be1e84872
commit a16722d221
4 changed files with 183 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

96
compiler/rustc_parse/src/parser/diagnostics.rs
View File

@ -21,6 +21,7 @@ use crate::errors::{
use crate::fluent_generated as fluent;
use crate::parser;
use crate::parser::attr::InnerAttrPolicy;
use rustc_ast as ast;
use rustc_ast::ptr::P;
use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
@ -722,6 +723,101 @@ impl<'a> Parser<'a> {
Err(err)
}
pub(super) fn attr_on_non_tail_expr(&self, expr: &Expr) {
// Missing semicolon typo error.
let span = self.prev_token.span.shrink_to_hi();
let mut err = self.sess.create_err(ExpectedSemi {
span,
token: self.token.clone(),
unexpected_token_label: Some(self.token.span),
sugg: ExpectedSemiSugg::AddSemi(span),
});
let attr_span = match &expr.attrs[..] {
[] => unreachable!(),
[only] => only.span,
[first, rest @ ..] => {
for attr in rest {
err.span_label(attr.span, "");
}
first.span
}
};
err.span_label(
attr_span,
format!(
"only `;` terminated statements or tail expressions are allowed after {}",
if expr.attrs.len() == 1 { "this attribute" } else { "these attributes" },
),
);
if self.token == token::Pound
&& self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Bracket))
{
// We have
// #[attr]
// expr
// #[not_attr]
// other_expr
err.span_label(span, "expected `;` here");
err.multipart_suggestion(
"alternatively, consider surrounding the expression with a block",
vec![
(expr.span.shrink_to_lo(), "{ ".to_string()),
(expr.span.shrink_to_hi(), " }".to_string()),
],
Applicability::MachineApplicable,
);
let mut snapshot = self.create_snapshot_for_diagnostic();
if let [attr] = &expr.attrs[..]
&& let ast::AttrKind::Normal(attr_kind) = &attr.kind
&& let [segment] = &attr_kind.item.path.segments[..]
&& segment.ident.name == sym::cfg
&& let Ok(next_attr) = snapshot.parse_attribute(InnerAttrPolicy::Forbidden(None))
&& let ast::AttrKind::Normal(next_attr_kind) = next_attr.kind
&& let [next_segment] = &next_attr_kind.item.path.segments[..]
&& segment.ident.name == sym::cfg
&& let Ok(next_expr) = snapshot.parse_expr()
{
// We have for sure
// #[cfg(..)]
// expr
// #[cfg(..)]
// other_expr
// So we suggest using `if cfg!(..) { expr } else if cfg!(..) { other_expr }`.
let margin = self.sess.source_map().span_to_margin(next_expr.span).unwrap_or(0);
let sugg = vec![
(attr.span.with_hi(segment.span().hi()), "if cfg!".to_string()),
(
attr_kind.item.args.span().unwrap().shrink_to_hi().with_hi(attr.span.hi()),
" {".to_string(),
),
(expr.span.shrink_to_lo(), " ".to_string()),
(
next_attr.span.with_hi(next_segment.span().hi()),
"} else if cfg!".to_string(),
),
(
next_attr_kind
.item
.args
.span()
.unwrap()
.shrink_to_hi()
.with_hi(next_attr.span.hi()),
" {".to_string(),
),
(next_expr.span.shrink_to_lo(), " ".to_string()),
(next_expr.span.shrink_to_hi(), format!("\n{}}}", " ".repeat(margin))),
];
err.multipart_suggestion(
"it seems like you are trying to provide different expressions depending on \
`cfg`, consider using `if cfg!(..)`",
sugg,
Applicability::MachineApplicable,
);
}
}
err.emit();
}
fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
let sm = self.sess.source_map();
match (&self.prev_token.kind, &self.token.kind) {

14
compiler/rustc_parse/src/parser/stmt.rs
View File

@ -617,6 +617,20 @@ impl<'a> Parser<'a> {
let mut add_semi_to_stmt = false;
match &mut stmt.kind {
// Expression without semicolon.
StmtKind::Expr(expr)
if classify::expr_requires_semi_to_be_stmt(expr)
&& !expr.attrs.is_empty()
&& ![token::Eof, token::Semi, token::CloseDelim(Delimiter::Brace)]
.contains(&self.token.kind) =>
{
// The user has written `#[attr] expr` which is unsupported. (#106020)
self.attr_on_non_tail_expr(&expr);
// We already emitted an error, so don't emit another type error
let sp = expr.span.to(self.prev_token.span);
*expr = self.mk_expr_err(sp);
}
// Expression without semicolon.
StmtKind::Expr(expr)
if self.token != token::Eof && classify::expr_requires_semi_to_be_stmt(expr) =>

19
tests/ui/parser/attribute/multiple-tail-expr-behind-cfg.rs Normal file
View File

@ -0,0 +1,19 @@
#![feature(stmt_expr_attributes)]
fn foo() -> String {
#[cfg(feature = "validation")]
[1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() //~ ERROR expected `;`, found `#`
#[cfg(not(feature = "validation"))]
String::new()
}
fn bar() -> String {
#[attr]
[1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() //~ ERROR expected `;`, found `#`
#[attr] //~ ERROR cannot find attribute `attr` in this scope
String::new()
}
fn main() {
println!("{}", foo());
}

54
tests/ui/parser/attribute/multiple-tail-expr-behind-cfg.stderr Normal file
View File

@ -0,0 +1,54 @@
error: expected `;`, found `#`
--> $DIR/multiple-tail-expr-behind-cfg.rs:5:64
|
LL | #[cfg(feature = "validation")]
| ------------------------------ only `;` terminated statements or tail expressions are allowed after this attribute
LL | [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
| ^ expected `;` here
LL | #[cfg(not(feature = "validation"))]
| - unexpected token
|
help: add `;` here
|
LL | [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
| +
help: alternatively, consider surrounding the expression with a block
|
LL | { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
| + +
help: it seems like you are trying to provide different expressions depending on `cfg`, consider using `if cfg!(..)`
|
LL ~ if cfg!(feature = "validation") {
LL ~ [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
LL ~ } else if cfg!(not(feature = "validation")) {
LL ~ String::new()
LL + }
|
error: expected `;`, found `#`
--> $DIR/multiple-tail-expr-behind-cfg.rs:12:64
|
LL | #[attr]
| ------- only `;` terminated statements or tail expressions are allowed after this attribute
LL | [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>()
| ^ expected `;` here
LL | #[attr]
| - unexpected token
|
help: add `;` here
|
LL | [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>();
| +
help: alternatively, consider surrounding the expression with a block
|
LL | { [1, 2, 3].iter().map(|c| c.to_string()).collect::<String>() }
| + +
error: cannot find attribute `attr` in this scope
--> $DIR/multiple-tail-expr-behind-cfg.rs:13:7
|
LL | #[attr]
| ^^^^
error: aborting due to 3 previous errors