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On format!() arg count mismatch provide extra info

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When positional width and precision formatting flags are present in a
formatting string that has an argument count mismatch, provide extra
information pointing at them making it easiser to understand where the
problem may lay:

```
error: 4 positional arguments in format string, but there are 3 arguments
  --> $DIR/ifmt-bad-arg.rs:78:15
   |
LL |     println!("{} {:.*} {}", 1, 3.2, 4);
   |               ^^ ^^--^ ^^      --- this parameter corresponds to the precision flag
   |                    |
   |                    this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
   |
   = note: positional arguments are zero-based
   = note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html

error: 4 positional arguments in format string, but there are 3 arguments
  --> $DIR/ifmt-bad-arg.rs:81:15
   |
LL |     println!("{} {:07$.*} {}", 1, 3.2, 4);
   |               ^^ ^^-----^ ^^      --- this parameter corresponds to the precision flag
   |                    |  |
   |                    |  this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
   |                    this width flag expects an `usize` argument at position 7, but there are 3 arguments
   |
   = note: positional arguments are zero-based
   = note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html

error: 3 positional arguments in format string, but there are 3 arguments
  --> $DIR/ifmt-bad-arg.rs:84:15
   |
LL |     println!("{} {:07$} {}", 1, 3.2, 4);
   |               ^^ ^^---^ ^^
   |                    |
   |                    this width flag expects an `usize` argument at position 7, but there are 3 arguments
   |
   = note: positional arguments are zero-based
   = note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
```
This commit is contained in:
Esteban Küber 2019-07-29 18:19:21 -07:00
parent c798dffac9
commit 159dcb2194
4 changed files with 206 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
src/libfmt_macros/lib.rs
View File

@ -59,16 +59,20 @@ pub struct Argument<'a> {
/// Specification for the formatting of an argument in the format string.
#[derive(Copy, Clone, PartialEq)]
pub struct FormatSpec<'a> {
/// Optionally specified character to fill alignment with
/// Optionally specified character to fill alignment with.
pub fill: Option<char>,
/// Optionally specified alignment
/// Optionally specified alignment.
pub align: Alignment,
/// Packed version of various flags provided
/// Packed version of various flags provided.
pub flags: u32,
/// The integer precision to use
/// The integer precision to use.
pub precision: Count,
/// The string width requested for the resulting format
/// The span of the precision formatting flag (for diagnostics).
pub precision_span: Option<InnerSpan>,
/// The string width requested for the resulting format.
pub width: Count,
/// The span of the width formatting flag (for diagnostics).
pub width_span: Option<InnerSpan>,
/// The descriptor string representing the name of the format desired for
/// this argument, this can be empty or any number of characters, although
/// it is required to be one word.
@ -285,19 +289,24 @@ impl<'a> Parser<'a> {
}
/// Optionally consumes the specified character. If the character is not at
/// the current position, then the current iterator isn't moved and false is
/// returned, otherwise the character is consumed and true is returned.
/// the current position, then the current iterator isn't moved and `false` is
/// returned, otherwise the character is consumed and `true` is returned.
fn consume(&mut self, c: char) -> bool {
if let Some(&(_, maybe)) = self.cur.peek() {
self.consume_pos(c).is_some()
}
/// Optionally consumes the specified character. If the character is not at
/// the current position, then the current iterator isn't moved and `None` is
/// returned, otherwise the character is consumed and the current position is
/// returned.
fn consume_pos(&mut self, c: char) -> Option<usize> {
if let Some(&(pos, maybe)) = self.cur.peek() {
if c == maybe {
self.cur.next();
true
} else {
false
return Some(pos);
}
} else {
false
}
None
}
fn to_span_index(&self, pos: usize) -> InnerOffset {
@ -465,7 +474,9 @@ impl<'a> Parser<'a> {
align: AlignUnknown,
flags: 0,
precision: CountImplied,
precision_span: None,
width: CountImplied,
width_span: None,
ty: &self.input[..0],
};
if !self.consume(':') {
@ -502,6 +513,11 @@ impl<'a> Parser<'a> {
}
// Width and precision
let mut havewidth = false;
let mut width_span_start = 0;
if let Some((pos, '0')) = self.cur.peek() {
width_span_start = *pos;
}
if self.consume('0') {
// small ambiguity with '0$' as a format string. In theory this is a
// '0' flag and then an ill-formatted format string with just a '$'
@ -515,17 +531,28 @@ impl<'a> Parser<'a> {
}
}
if !havewidth {
spec.width = self.count();
if width_span_start == 0 {
if let Some((pos, _)) = self.cur.peek() {
width_span_start = *pos;
}
}
let (w, sp) = self.count(width_span_start);
spec.width = w;
spec.width_span = sp;
}
if self.consume('.') {
if self.consume('*') {
if let Some(start) = self.consume_pos('.') {
if let Some(end) = self.consume_pos('*') {
// Resolve `CountIsNextParam`.
// We can do this immediately as `position` is resolved later.
let i = self.curarg;
self.curarg += 1;
spec.precision = CountIsParam(i);
spec.precision_span =
Some(self.to_span_index(start).to(self.to_span_index(end + 1)));
} else {
spec.precision = self.count();
let (p, sp) = self.count(start);
spec.precision = p;
spec.precision_span = sp;
}
}
// Optional radix followed by the actual format specifier
@ -554,24 +581,25 @@ impl<'a> Parser<'a> {
/// Parses a Count parameter at the current position. This does not check
/// for 'CountIsNextParam' because that is only used in precision, not
/// width.
fn count(&mut self) -> Count {
fn count(&mut self, start: usize) -> (Count, Option<InnerSpan>) {
if let Some(i) = self.integer() {
if self.consume('$') {
CountIsParam(i)
if let Some(end) = self.consume_pos('$') {
let span = self.to_span_index(start).to(self.to_span_index(end + 1));
(CountIsParam(i), Some(span))
} else {
CountIs(i)
(CountIs(i), None)
}
} else {
let tmp = self.cur.clone();
let word = self.word();
if word.is_empty() {
self.cur = tmp;
CountImplied
(CountImplied, None)
} else if self.consume('$') {
CountIsName(Symbol::intern(word))
(CountIsName(Symbol::intern(word)), None)
} else {
self.cur = tmp;
CountImplied
(CountImplied, None)
}
}
}

107
src/libsyntax_ext/format.rs
View File

@ -109,6 +109,8 @@ struct Context<'a, 'b> {
invalid_refs: Vec<(usize, usize)>,
/// Spans of all the formatting arguments, in order.
arg_spans: Vec<Span>,
/// All the formatting arguments that have formatting flags set, in order for diagnostics.
arg_with_formatting: Vec<parse::FormatSpec<'a>>,
/// Whether this formatting string is a literal or it comes from a macro.
is_literal: bool,
}
@ -279,14 +281,20 @@ impl<'a, 'b> Context<'a, 'b> {
.iter()
.map(|(r, pos)| (r.to_string(), self.arg_spans.get(*pos)));
let mut zero_based_note = false;
if self.names.is_empty() && !numbered_position_args {
let count = self.pieces.len() + self.arg_with_formatting
.iter()
.filter(|fmt| fmt.precision_span.is_some())
.count();
e = self.ecx.mut_span_err(
sp,
&format!(
"{} positional argument{} in format string, but {}",
self.pieces.len(),
if self.pieces.len() > 1 { "s" } else { "" },
self.describe_num_args()
count,
if count > 1 { "s" } else { "" },
self.describe_num_args(),
),
);
} else {
@ -317,9 +325,70 @@ impl<'a, 'b> Context<'a, 'b> {
&format!("invalid reference to positional {} ({})",
arg_list,
self.describe_num_args()));
e.note("positional arguments are zero-based");
zero_based_note = true;
};
for fmt in &self.arg_with_formatting {
if let Some(span) = fmt.precision_span {
let span = self.fmtsp.from_inner(span);
match fmt.precision {
parse::CountIsParam(pos) if pos > self.args.len() => {
e.span_label(span, &format!(
"this precision flag expects an `usize` argument at position {}, \
but {}",
pos,
self.describe_num_args(),
));
zero_based_note = true;
}
parse::CountIsParam(pos) => {
let count = self.pieces.len() + self.arg_with_formatting
.iter()
.filter(|fmt| fmt.precision_span.is_some())
.count();
e.span_label(span, &format!(
"this precision flag adds an extra required argument at position {}, \
which is why there {} expected",
pos,
if count == 1 {
"is 1 argument".to_string()
} else {
format!("are {} arguments", count)
},
));
e.span_label(
self.args[pos].span,
"this parameter corresponds to the precision flag",
);
zero_based_note = true;
}
_ => {}
}
}
if let Some(span) = fmt.width_span {
let span = self.fmtsp.from_inner(span);
match fmt.width {
parse::CountIsParam(pos) if pos > self.args.len() => {
e.span_label(span, &format!(
"this width flag expects an `usize` argument at position {}, \
but {}",
pos,
self.describe_num_args(),
));
zero_based_note = true;
}
_ => {}
}
}
}
if zero_based_note {
e.note("positional arguments are zero-based");
}
if !self.arg_with_formatting.is_empty() {
e.note("for information about formatting flags, visit \
https://doc.rust-lang.org/std/fmt/index.html");
}
e.emit();
}
@ -435,10 +504,11 @@ impl<'a, 'b> Context<'a, 'b> {
/// Builds a static `rt::Argument` from a `parse::Piece` or append
/// to the `literal` string.
fn build_piece(&mut self,
piece: &parse::Piece<'_>,
arg_index_consumed: &mut Vec<usize>)
-> Option<P<ast::Expr>> {
fn build_piece(
&mut self,
piece: &parse::Piece<'a>,
arg_index_consumed: &mut Vec<usize>,
) -> Option<P<ast::Expr>> {
let sp = self.macsp;
match *piece {
parse::String(s) => {
@ -496,7 +566,9 @@ impl<'a, 'b> Context<'a, 'b> {
align: parse::AlignUnknown,
flags: 0,
precision: parse::CountImplied,
precision_span: None,
width: parse::CountImplied,
width_span: None,
ty: arg.format.ty,
},
};
@ -506,6 +578,9 @@ impl<'a, 'b> Context<'a, 'b> {
let pos_simple =
arg.position.index() == simple_arg.position.index();
if arg.format.precision_span.is_some() || arg.format.width_span.is_some() {
self.arg_with_formatting.push(arg.format); //'liself.fmtsp.from_inner(span));
}
if !pos_simple || arg.format != simple_arg.format || fill != ' ' {
self.all_pieces_simple = false;
}
@ -530,7 +605,7 @@ impl<'a, 'b> Context<'a, 'b> {
let path = self.ecx.path_global(sp, Context::rtpath(self.ecx, "FormatSpec"));
let fmt = self.ecx.expr_struct(
sp,
path,
path,
vec![
self.ecx.field_imm(sp, self.ecx.ident_of("fill"), fill),
self.ecx.field_imm(sp, self.ecx.ident_of("align"), align),
@ -657,12 +732,13 @@ impl<'a, 'b> Context<'a, 'b> {
self.ecx.expr_call_global(self.macsp, path, fn_args)
}
fn format_arg(ecx: &ExtCtxt<'_>,
macsp: Span,
mut sp: Span,
ty: &ArgumentType,
arg: ast::Ident)
-> P<ast::Expr> {
fn format_arg(
ecx: &ExtCtxt<'_>,
macsp: Span,
mut sp: Span,
ty: &ArgumentType,
arg: ast::Ident,
) -> P<ast::Expr> {
sp = sp.apply_mark(ecx.current_expansion.id);
let arg = ecx.expr_ident(sp, arg);
let trait_ = match *ty {
@ -941,6 +1017,7 @@ pub fn expand_preparsed_format_args(
fmtsp: fmt.span,
invalid_refs: Vec::new(),
arg_spans,
arg_with_formatting: Vec::new(),
is_literal,
};

8
src/test/ui/if/ifmt-bad-arg.rs
View File

@ -75,4 +75,12 @@ ninth number: {
tenth number: {}",
1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
//~^^ ERROR: invalid format string
println!("{} {:.*} {}", 1, 3.2, 4);
//~^ ERROR 4 positional arguments in format string, but there are 3 arguments
//~| ERROR mismatched types
println!("{} {:07$.*} {}", 1, 3.2, 4);
//~^ ERROR 4 positional arguments in format string, but there are 3 arguments
//~| ERROR mismatched types
println!("{} {:07$} {}", 1, 3.2, 4);
//~^ ERROR 3 positional arguments in format string, but there are 3 arguments
}

55
src/test/ui/if/ifmt-bad-arg.stderr
View File

@ -220,5 +220,58 @@ LL | tenth number: {}",
|
= note: if you intended to print `{`, you can escape it using `{{`
error: aborting due to 28 previous errors
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:78:15
|
LL | println!("{} {:.*} {}", 1, 3.2, 4);
| ^^ ^^--^ ^^ --- this parameter corresponds to the precision flag
| |
| this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: 4 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:81:15
|
LL | println!("{} {:07$.*} {}", 1, 3.2, 4);
| ^^ ^^-----^ ^^ --- this parameter corresponds to the precision flag
| | |
| | this precision flag adds an extra required argument at position 1, which is why there are 4 arguments expected
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error: 3 positional arguments in format string, but there are 3 arguments
--> $DIR/ifmt-bad-arg.rs:84:15
|
LL | println!("{} {:07$} {}", 1, 3.2, 4);
| ^^ ^^---^ ^^
| |
| this width flag expects an `usize` argument at position 7, but there are 3 arguments
|
= note: positional arguments are zero-based
= note: for information about formatting flags, visit https://doc.rust-lang.org/std/fmt/index.html
error[E0308]: mismatched types
--> $DIR/ifmt-bad-arg.rs:78:32
|
LL | println!("{} {:.*} {}", 1, 3.2, 4);
| ^^^ expected usize, found floating-point number
|
= note: expected type `&usize`
found type `&{float}`
error[E0308]: mismatched types
--> $DIR/ifmt-bad-arg.rs:81:35
|
LL | println!("{} {:07$.*} {}", 1, 3.2, 4);
| ^^^ expected usize, found floating-point number
|
= note: expected type `&usize`
found type `&{float}`
error: aborting due to 33 previous errors
For more information about this error, try `rustc --explain E0308`.