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Specific error for positional args after named args in format!()

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When writing positional arguments after named arguments in the
`format!()` and `println!()` macros, provide a targeted diagnostic.
This commit is contained in:
Esteban Küber 2019-07-15 20:51:32 -07:00
parent 4b65a86eba
commit 33ec1823d7
5 changed files with 53 additions and 34 deletions
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39
src/libsyntax_ext/format.rs
View File

@ -146,16 +146,13 @@ fn parse_args<'a>(
if p.token == token::Eof {
break;
} // accept trailing commas
if named || (p.token.is_ident() && p.look_ahead(1, |t| *t == token::Eq)) {
if p.token.is_ident() && p.look_ahead(1, |t| *t == token::Eq) {
named = true;
let name = if let token::Ident(name, _) = p.token.kind {
p.bump();
name
} else {
return Err(ecx.struct_span_err(
p.token.span,
"expected ident, positional arguments cannot follow named arguments",
));
unreachable!();
};
p.expect(&token::Eq)?;
@ -176,6 +173,17 @@ fn parse_args<'a>(
args.push(e);
} else {
let e = p.parse_expr()?;
if named {
let mut err = ecx.struct_span_err(
e.span,
"positional arguments cannot follow named arguments",
);
err.span_label(e.span, "positional arguments must be before named arguments");
for (_, pos) in &names {
err.span_label(args[*pos].span, "named argument");
}
err.emit();
}
args.push(e);
}
}
@ -721,13 +729,14 @@ pub fn expand_format_args_nl<'cx>(
/// Take the various parts of `format_args!(efmt, args..., name=names...)`
/// and construct the appropriate formatting expression.
pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt<'_>,
sp: Span,
efmt: P<ast::Expr>,
args: Vec<P<ast::Expr>>,
names: FxHashMap<Symbol, usize>,
append_newline: bool)
-> P<ast::Expr> {
pub fn expand_preparsed_format_args(
ecx: &mut ExtCtxt<'_>,
sp: Span,
efmt: P<ast::Expr>,
args: Vec<P<ast::Expr>>,
names: FxHashMap<Symbol, usize>,
append_newline: bool,
) -> P<ast::Expr> {
// NOTE: this verbose way of initializing `Vec<Vec<ArgumentType>>` is because
// `ArgumentType` does not derive `Clone`.
let arg_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
@ -906,6 +915,8 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt<'_>,
.map(|span| fmt.span.from_inner(*span))
.collect();
let named_pos: FxHashSet<usize> = names.values().cloned().collect();
let mut cx = Context {
ecx,
args,
@ -971,14 +982,12 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt<'_>,
}
// Make sure that all arguments were used and all arguments have types.
let num_pos_args = cx.args.len() - cx.names.len();
let errs = cx.arg_types
.iter()
.enumerate()
.filter(|(i, ty)| ty.is_empty() && !cx.count_positions.contains_key(&i))
.map(|(i, _)| {
let msg = if i >= num_pos_args {
let msg = if named_pos.contains(&i) {
// named argument
"named argument never used"
} else {

2
src/test/ui/if/ifmt-bad-arg.rs
View File

@ -38,7 +38,7 @@ fn main() {
format!("{} {}", 1, 2, foo=1, bar=2); //~ ERROR: multiple unused formatting arguments
format!("{foo}", foo=1, foo=2); //~ ERROR: duplicate argument
format!("", foo=1, 2); //~ ERROR: positional arguments cannot follow
format!("{foo} {} {}", foo=1, 2); //~ ERROR: positional arguments cannot follow
// bad named arguments, #35082

10
src/test/ui/if/ifmt-bad-arg.stderr
View File

@ -146,11 +146,13 @@ note: previously here
LL | format!("{foo}", foo=1, foo=2);
| ^
error: expected ident, positional arguments cannot follow named arguments
--> $DIR/ifmt-bad-arg.rs:41:24
error: positional arguments cannot follow named arguments
--> $DIR/ifmt-bad-arg.rs:41:35
|
LL | format!("", foo=1, 2);
| ^
LL | format!("{foo} {} {}", foo=1, 2);
| - ^ positional arguments must be before named arguments
| |
| named argument
error: there is no argument named `valueb`
--> $DIR/ifmt-bad-arg.rs:45:23

10
src/test/ui/macros/format-parse-errors.rs
View File

@ -1,9 +1,15 @@
fn main() {
let foo = "";
let bar = "";
format!(); //~ ERROR requires at least a format string argument
format!(struct); //~ ERROR expected expression
format!("s", name =); //~ ERROR expected expression
format!("s", foo = foo, bar); //~ ERROR expected `=`
format!("s", foo = struct); //~ ERROR expected expression
format!(
"s {foo} {} {}",
foo = foo,
bar, //~ ERROR positional arguments cannot follow named arguments
);
format!("s {foo}", foo = struct); //~ ERROR expected expression
format!("s", struct); //~ ERROR expected expression
// This error should come after parsing errors to ensure they are non-fatal.

26
src/test/ui/macros/format-parse-errors.stderr
View File

@ -1,5 +1,5 @@
error: requires at least a format string argument
--> $DIR/format-parse-errors.rs:2:5
--> $DIR/format-parse-errors.rs:4:5
|
LL | format!();
| ^^^^^^^^^^
@ -7,37 +7,39 @@ LL | format!();
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error: expected expression, found keyword `struct`
--> $DIR/format-parse-errors.rs:3:13
--> $DIR/format-parse-errors.rs:5:13
|
LL | format!(struct);
| ^^^^^^ expected expression
error: expected expression, found end of macro arguments
--> $DIR/format-parse-errors.rs:4:24
--> $DIR/format-parse-errors.rs:6:24
|
LL | format!("s", name =);
| ^ expected expression
error: expected `=`, found end of macro arguments
--> $DIR/format-parse-errors.rs:5:32
error: positional arguments cannot follow named arguments
--> $DIR/format-parse-errors.rs:10:9
|
LL | format!("s", foo = foo, bar);
| ^ expected `=`
LL | foo = foo,
| --- named argument
LL | bar,
| ^^^ positional arguments must be before named arguments
error: expected expression, found keyword `struct`
--> $DIR/format-parse-errors.rs:6:24
--> $DIR/format-parse-errors.rs:12:30
|
LL | format!("s", foo = struct);
| ^^^^^^ expected expression
LL | format!("s {foo}", foo = struct);
| ^^^^^^ expected expression
error: expected expression, found keyword `struct`
--> $DIR/format-parse-errors.rs:7:18
--> $DIR/format-parse-errors.rs:13:18
|
LL | format!("s", struct);
| ^^^^^^ expected expression
error: format argument must be a string literal
--> $DIR/format-parse-errors.rs:10:13
--> $DIR/format-parse-errors.rs:16:13
|
LL | format!(123);
| ^^^