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Improve suggestion for missing fmt str in println

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Avoid using `concat!(fmt, "\n")` to improve the diagnostics being
emitted when the first `println!()` argument isn't a formatting string
literal.
This commit is contained in:
Esteban Küber
2018-07-14 20:50:30 -07:00
committed by Esteban Küber
parent bc14d71622
commit f53c145ef1
14 changed files with 122 additions and 102 deletions
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28
src/libsyntax_ext/format.rs
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@@ -703,10 +703,24 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
let mut macsp = ecx.call_site();
macsp = macsp.apply_mark(ecx.current_expansion.mark);
let msg = "format argument must be a string literal.";
let msg = "format argument must be a string literal";
let fmt_sp = efmt.span;
let fmt = match expr_to_spanned_string(ecx, efmt, msg) {
Some(fmt) => fmt,
None => return DummyResult::raw_expr(sp),
Ok(fmt) => fmt,
Err(mut err) => {
let sugg_fmt = match args.len() {
0 => "{}".to_string(),
_ => format!("{}{{}}", "{}, ".repeat(args.len())),
};
err.span_suggestion(
fmt_sp.shrink_to_lo(),
"you might be missing a string literal to format with",
format!("\"{}\", ", sugg_fmt),
);
err.emit();
return DummyResult::raw_expr(sp);
},
};
let mut cx = Context {
@@ -818,7 +832,7 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
errs.iter().map(|&(sp, _)| sp).collect::<Vec<Span>>(),
"multiple unused formatting arguments"
);
diag.span_label(cx.fmtsp, "multiple unused arguments in this statement");
diag.span_label(cx.fmtsp, "multiple missing formatting arguments");
diag
}
};
@@ -861,8 +875,10 @@ pub fn expand_preparsed_format_args(ecx: &mut ExtCtxt,
}
if show_doc_note {
diag.note(concat!(stringify!($kind), " formatting not supported; see \
the documentation for `std::fmt`"));
diag.note(concat!(
stringify!($kind),
" formatting not supported; see the documentation for `std::fmt`",
));
}
}};
}