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authoredJul 13, 2016
Auto merge of #33642 - xen0n:ergonomic-format-macro, r=alexcrichton
Ergonomic format_args! Fixes #9456 (at last). Not a ground-up rewrite of the existing machinery, but more like an added intermediary layer between macro arguments and format placeholders. This is now implementing Rust RFC 1618!
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1.85.11.12.0
2 parents 0b7fb80 + 51e54e5 commit db71987

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5 files changed

+321
-199
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5 files changed

+321
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‎src/libfmt_macros/lib.rs

+42-20
Original file line numberDiff line numberDiff line change
@@ -80,8 +80,6 @@ pub struct FormatSpec<'a> {
8080
/// Enum describing where an argument for a format can be located.
8181
#[derive(Copy, Clone, PartialEq)]
8282
pub enum Position<'a> {
83-
/// The argument will be in the next position. This is the default.
84-
ArgumentNext,
8583
/// The argument is located at a specific index.
8684
ArgumentIs(usize),
8785
/// The argument has a name.
@@ -127,8 +125,6 @@ pub enum Count<'a> {
127125
CountIsName(&'a str),
128126
/// The count is specified by the argument at the given index.
129127
CountIsParam(usize),
130-
/// The count is specified by the next parameter.
131-
CountIsNextParam,
132128
/// The count is implied and cannot be explicitly specified.
133129
CountImplied,
134130
}
@@ -144,6 +140,8 @@ pub struct Parser<'a> {
144140
cur: iter::Peekable<str::CharIndices<'a>>,
145141
/// Error messages accumulated during parsing
146142
pub errors: Vec<string::String>,
143+
/// Current position of implicit positional argument pointer
144+
curarg: usize,
147145
}
148146

149147
impl<'a> Iterator for Parser<'a> {
@@ -186,6 +184,7 @@ impl<'a> Parser<'a> {
186184
input: s,
187185
cur: s.char_indices().peekable(),
188186
errors: vec![],
187+
curarg: 0,
189188
}
190189
}
191190

@@ -259,21 +258,40 @@ impl<'a> Parser<'a> {
259258
/// Parses an Argument structure, or what's contained within braces inside
260259
/// the format string
261260
fn argument(&mut self) -> Argument<'a> {
261+
let pos = self.position();
262+
let format = self.format();
263+
264+
// Resolve position after parsing format spec.
265+
let pos = match pos {
266+
Some(position) => position,
267+
None => {
268+
let i = self.curarg;
269+
self.curarg += 1;
270+
ArgumentIs(i)
271+
}
272+
};
273+
262274
Argument {
263-
position: self.position(),
264-
format: self.format(),
275+
position: pos,
276+
format: format,
265277
}
266278
}
267279

268280
/// Parses a positional argument for a format. This could either be an
269281
/// integer index of an argument, a named argument, or a blank string.
270-
fn position(&mut self) -> Position<'a> {
282+
/// Returns `Some(parsed_position)` if the position is not implicitly
283+
/// consuming a macro argument, `None` if it's the case.
284+
fn position(&mut self) -> Option<Position<'a>> {
271285
if let Some(i) = self.integer() {
272-
ArgumentIs(i)
286+
Some(ArgumentIs(i))
273287
} else {
274288
match self.cur.peek() {
275-
Some(&(_, c)) if c.is_alphabetic() => ArgumentNamed(self.word()),
276-
_ => ArgumentNext,
289+
Some(&(_, c)) if c.is_alphabetic() => Some(ArgumentNamed(self.word())),
290+
291+
// This is an `ArgumentNext`.
292+
// Record the fact and do the resolution after parsing the
293+
// format spec, to make things like `{:.*}` work.
294+
_ => None,
277295
}
278296
}
279297
}
@@ -340,7 +358,11 @@ impl<'a> Parser<'a> {
340358
}
341359
if self.consume('.') {
342360
if self.consume('*') {
343-
spec.precision = CountIsNextParam;
361+
// Resolve `CountIsNextParam`.
362+
// We can do this immediately as `position` is resolved later.
363+
let i = self.curarg;
364+
self.curarg += 1;
365+
spec.precision = CountIsParam(i);
344366
} else {
345367
spec.precision = self.count();
346368
}
@@ -487,7 +509,7 @@ mod tests {
487509
fn format_nothing() {
488510
same("{}",
489511
&[NextArgument(Argument {
490-
position: ArgumentNext,
512+
position: ArgumentIs(0),
491513
format: fmtdflt(),
492514
})]);
493515
}
@@ -565,7 +587,7 @@ mod tests {
565587
fn format_counts() {
566588
same("{:10s}",
567589
&[NextArgument(Argument {
568-
position: ArgumentNext,
590+
position: ArgumentIs(0),
569591
format: FormatSpec {
570592
fill: None,
571593
align: AlignUnknown,
@@ -577,7 +599,7 @@ mod tests {
577599
})]);
578600
same("{:10$.10s}",
579601
&[NextArgument(Argument {
580-
position: ArgumentNext,
602+
position: ArgumentIs(0),
581603
format: FormatSpec {
582604
fill: None,
583605
align: AlignUnknown,
@@ -589,19 +611,19 @@ mod tests {
589611
})]);
590612
same("{:.*s}",
591613
&[NextArgument(Argument {
592-
position: ArgumentNext,
614+
position: ArgumentIs(1),
593615
format: FormatSpec {
594616
fill: None,
595617
align: AlignUnknown,
596618
flags: 0,
597-
precision: CountIsNextParam,
619+
precision: CountIsParam(0),
598620
width: CountImplied,
599621
ty: "s",
600622
},
601623
})]);
602624
same("{:.10$s}",
603625
&[NextArgument(Argument {
604-
position: ArgumentNext,
626+
position: ArgumentIs(0),
605627
format: FormatSpec {
606628
fill: None,
607629
align: AlignUnknown,
@@ -613,7 +635,7 @@ mod tests {
613635
})]);
614636
same("{:a$.b$s}",
615637
&[NextArgument(Argument {
616-
position: ArgumentNext,
638+
position: ArgumentIs(0),
617639
format: FormatSpec {
618640
fill: None,
619641
align: AlignUnknown,
@@ -628,7 +650,7 @@ mod tests {
628650
fn format_flags() {
629651
same("{:-}",
630652
&[NextArgument(Argument {
631-
position: ArgumentNext,
653+
position: ArgumentIs(0),
632654
format: FormatSpec {
633655
fill: None,
634656
align: AlignUnknown,
@@ -640,7 +662,7 @@ mod tests {
640662
})]);
641663
same("{:+#}",
642664
&[NextArgument(Argument {
643-
position: ArgumentNext,
665+
position: ArgumentIs(0),
644666
format: FormatSpec {
645667
fill: None,
646668
align: AlignUnknown,

‎src/librustc_typeck/check/mod.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -881,7 +881,7 @@ fn check_on_unimplemented<'a, 'tcx>(ccx: &CrateCtxt<'a, 'tcx>,
881881
}
882882
},
883883
// `{:1}` and `{}` are not to be used
884-
Position::ArgumentIs(_) | Position::ArgumentNext => {
884+
Position::ArgumentIs(_) => {
885885
span_err!(ccx.tcx.sess, attr.span, E0231,
886886
"only named substitution \
887887
parameters are allowed");

‎src/libsyntax_ext/format.rs

+245-175
Large diffs are not rendered by default.

‎src/test/compile-fail/ifmt-bad-arg.rs

-3
Original file line numberDiff line numberDiff line change
@@ -23,9 +23,6 @@ fn main() {
2323
format!("{foo}", 1, foo=2); //~ ERROR: argument never used
2424
format!("", foo=2); //~ ERROR: named argument never used
2525

26-
format!("{0:x} {0:X}", 1); //~ ERROR: redeclared with type `X`
27-
format!("{foo:x} {foo:X}", foo=1); //~ ERROR: redeclared with type `X`
28-
2926
format!("{foo}", foo=1, foo=2); //~ ERROR: duplicate argument
3027
format!("", foo=1, 2); //~ ERROR: positional arguments cannot follow
3128

‎src/test/run-pass/ifmt.rs

+33
Original file line numberDiff line numberDiff line change
@@ -163,6 +163,24 @@ pub fn main() {
163163
t!(format!("{:?}", 0.0), "0");
164164

165165

166+
// Ergonomic format_args!
167+
t!(format!("{0:x} {0:X}", 15), "f F");
168+
t!(format!("{0:x} {0:X} {}", 15), "f F 15");
169+
// NOTE: For now the longer test cases must not be followed immediately by
170+
// >1 empty lines, or the pretty printer will break. Since no one wants to
171+
// touch the current pretty printer (#751), we have no choice but to work
172+
// around it. Some of the following test cases are also affected.
173+
t!(format!("{:x}{0:X}{a:x}{:X}{1:x}{a:X}", 13, 14, a=15), "dDfEeF");
174+
t!(format!("{a:x} {a:X}", a=15), "f F");
175+
176+
// And its edge cases
177+
t!(format!("{a:.0$} {b:.0$} {0:.0$}\n{a:.c$} {b:.c$} {c:.c$}",
178+
4, a="abcdefg", b="hijklmn", c=3),
179+
"abcd hijk 4\nabc hij 3");
180+
t!(format!("{a:.*} {0} {:.*}", 4, 3, "efgh", a="abcdef"), "abcd 4 efg");
181+
t!(format!("{:.a$} {a} {a:#x}", "aaaaaa", a=2), "aa 2 0x2");
182+
183+
166184
// Test that pointers don't get truncated.
167185
{
168186
let val = usize::MAX;
@@ -177,6 +195,7 @@ pub fn main() {
177195
test_write();
178196
test_print();
179197
test_order();
198+
test_once();
180199

181200
// make sure that format! doesn't move out of local variables
182201
let a: Box<_> = box 3;
@@ -260,3 +279,17 @@ fn test_order() {
260279
foo(), foo(), foo(), a=foo(), b=foo(), c=foo()),
261280
"1 2 4 5 3 6".to_string());
262281
}
282+
283+
fn test_once() {
284+
// Make sure each argument are evaluted only once even though it may be
285+
// formatted multiple times
286+
fn foo() -> isize {
287+
static mut FOO: isize = 0;
288+
unsafe {
289+
FOO += 1;
290+
FOO
291+
}
292+
}
293+
assert_eq!(format!("{0} {0} {0} {a} {a} {a}", foo(), a=foo()),
294+
"1 1 1 2 2 2".to_string());
295+
}

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