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Improve suggestion for missing fmt str in println 

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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10
src/libstd/macros.rs
View File

@ -155,8 +155,14 @@ macro_rules! print {
#[stable(feature = "rust1", since = "1.0.0")]
macro_rules! println {
() => (print!("\n"));
($fmt:expr) => (print!(concat!($fmt, "\n")));
($fmt:expr, $($arg:tt)*) => (print!(concat!($fmt, "\n"), $($arg)*));
($fmt:expr) => ({
print!($fmt);
print!("\n");
});
($fmt:expr, $($arg:tt)*) => ({
print!($fmt, $($arg)*);
print!("\n");
});
}
/// Macro for printing to the standard error.

25
src/libsyntax/ext/base.rs
View File

@ -959,29 +959,34 @@ impl<'a> ExtCtxt<'a> {
/// Extract a string literal from the macro expanded version of `expr`,
/// emitting `err_msg` if `expr` is not a string literal. This does not stop
/// compilation on error, merely emits a non-fatal error and returns None.
pub fn expr_to_spanned_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
-> Option<Spanned<(Symbol, ast::StrStyle)>> {
pub fn expr_to_spanned_string<'a>(
cx: &'a mut ExtCtxt,
expr: P<ast::Expr>,
err_msg: &str,
) -> Result<Spanned<(Symbol, ast::StrStyle)>, DiagnosticBuilder<'a>> {
// Update `expr.span`'s ctxt now in case expr is an `include!` macro invocation.
let expr = expr.map(|mut expr| {
expr.span = expr.span.apply_mark(cx.current_expansion.mark);
expr
});
// we want to be able to handle e.g. concat("foo", "bar")
// we want to be able to handle e.g. `concat!("foo", "bar")`
let expr = cx.expander().fold_expr(expr);
match expr.node {
Err(match expr.node {
ast::ExprKind::Lit(ref l) => match l.node {
ast::LitKind::Str(s, style) => return Some(respan(expr.span, (s, style))),
_ => cx.span_err(l.span, err_msg)
ast::LitKind::Str(s, style) => return Ok(respan(expr.span, (s, style))),
_ => cx.struct_span_err(l.span, err_msg)
},
_ => cx.span_err(expr.span, err_msg)
}
None
_ => cx.struct_span_err(expr.span, err_msg)
})
}
pub fn expr_to_string(cx: &mut ExtCtxt, expr: P<ast::Expr>, err_msg: &str)
-> Option<(Symbol, ast::StrStyle)> {
expr_to_spanned_string(cx, expr, err_msg).map(|s| s.node)
expr_to_spanned_string(cx, expr, err_msg)
.map_err(|mut err| err.emit())
.ok()
.map(|s| s.node)
}
/// Non-fatally assert that `tts` is empty. Note that this function

15
src/libsyntax_ext/concat.rs
View File

@ -27,6 +27,7 @@ pub fn expand_syntax_ext(
None => return base::DummyResult::expr(sp),
};
let mut accumulator = String::new();
let mut missing_literal = vec![];
for e in es {
match e.node {
ast::ExprKind::Lit(ref lit) => match lit.node {
@ -51,17 +52,15 @@ pub fn expand_syntax_ext(
}
},
_ => {
let mut err = cx.struct_span_err(e.span, "expected a literal");
let snippet = cx.codemap().span_to_snippet(e.span).unwrap();
err.span_suggestion(
e.span,
"you might be missing a string literal to format with",
format!("\"{{}}\", {}", snippet),
);
err.emit();
missing_literal.push(e.span);
}
}
}
if missing_literal.len() > 0 {
let mut err = cx.struct_span_err(missing_literal, "expected a literal");
err.note("only `&str` literals can be passed to `concat!()`");
err.emit();
}
let sp = sp.apply_mark(cx.current_expansion.mark);
base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
}

28
src/libsyntax_ext/format.rs
View File

@ -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`",
));
}
}};
}

14
src/test/ui/const-eval/conditional_array_execution.nll.stderr
View File

@ -28,25 +28,19 @@ LL | println!("{}", FOO);
| ^^^ referenced constant has errors
error[E0080]: referenced constant has errors
--> $DIR/conditional_array_execution.rs:19:5
--> $DIR/conditional_array_execution.rs:19:14
|
LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
| ----- attempt to subtract with overflow
...
LL | println!("{}", FOO);
| ^^^^^^^^^^^^^^^^^^^^
|
= 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[E0080]: erroneous constant used
--> $DIR/conditional_array_execution.rs:19:5
--> $DIR/conditional_array_execution.rs:19:14
|
LL | println!("{}", FOO);
| ^^^^^^^^^^^^^^^---^^
| |
| referenced constant has errors
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^ --- referenced constant has errors
error[E0080]: referenced constant has errors
--> $DIR/conditional_array_execution.rs:19:20

14
src/test/ui/const-eval/issue-43197.nll.stderr
View File

@ -51,25 +51,19 @@ LL | println!("{} {}", X, Y);
| ^ referenced constant has errors
error[E0080]: referenced constant has errors
--> $DIR/issue-43197.rs:24:5
--> $DIR/issue-43197.rs:24:14
|
LL | const X: u32 = 0-1;
| --- attempt to subtract with overflow
...
LL | println!("{} {}", X, Y);
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
= 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[E0080]: erroneous constant used
--> $DIR/issue-43197.rs:24:5
--> $DIR/issue-43197.rs:24:14
|
LL | println!("{} {}", X, Y);
| ^^^^^^^^^^^^^^^^^^-^^^^^
| |
| referenced constant has errors
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^^^^ - referenced constant has errors
error[E0080]: referenced constant has errors
--> $DIR/issue-43197.rs:24:26

14
src/test/ui/const-eval/issue-44578.nll.stderr
View File

@ -1,23 +1,17 @@
error[E0080]: referenced constant has errors
--> $DIR/issue-44578.rs:35:5
--> $DIR/issue-44578.rs:35:14
|
LL | const AMT: usize = [A::AMT][(A::AMT > B::AMT) as usize];
| ------------------------------------ index out of bounds: the len is 1 but the index is 1
...
LL | println!("{}", <Bar<u16, u8> as Foo>::AMT);
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= 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[E0080]: erroneous constant used
--> $DIR/issue-44578.rs:35:5
--> $DIR/issue-44578.rs:35:14
|
LL | println!("{}", <Bar<u16, u8> as Foo>::AMT);
| ^^^^^^^^^^^^^^^--------------------------^^
| |
| referenced constant has errors
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ^^^^ -------------------------- referenced constant has errors
error[E0080]: referenced constant has errors
--> $DIR/issue-44578.rs:35:20

2
src/test/ui/fmt/format-string-error.rs
View File

@ -10,8 +10,10 @@
fn main() {
println!("{");
//~^ ERROR invalid format string: expected `'}'` but string was terminated
println!("{{}}");
println!("}");
//~^ ERROR invalid format string: unmatched `}` found
let _ = format!("{_foo}", _foo = 6usize);
//~^ ERROR invalid format string: invalid argument name `_foo`
let _ = format!("{_}", _ = 6usize);

20
src/test/ui/fmt/format-string-error.stderr
View File

@ -1,23 +1,21 @@
error: invalid format string: expected `'}'` but string was terminated
--> $DIR/format-string-error.rs:12:5
--> $DIR/format-string-error.rs:12:16
|
LL | println!("{");
| ^^^^^^^^^^^^^^ expected `'}'` in format string
| ^ expected `'}'` in format string
|
= note: if you intended to print `{`, you can escape it using `{{`
= 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: invalid format string: unmatched `}` found
--> $DIR/format-string-error.rs:14:5
--> $DIR/format-string-error.rs:15:15
|
LL | println!("}");
| ^^^^^^^^^^^^^^ unmatched `}` in format string
| ^ unmatched `}` in format string
|
= note: if you intended to print `}`, you can escape it using `}}`
= 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: invalid format string: invalid argument name `_foo`
--> $DIR/format-string-error.rs:15:23
--> $DIR/format-string-error.rs:17:23
|
LL | let _ = format!("{_foo}", _foo = 6usize);
| ^^^^ invalid argument name in format string
@ -25,7 +23,7 @@ LL | let _ = format!("{_foo}", _foo = 6usize);
= note: argument names cannot start with an underscore
error: invalid format string: invalid argument name `_`
--> $DIR/format-string-error.rs:17:23
--> $DIR/format-string-error.rs:19:23
|
LL | let _ = format!("{_}", _ = 6usize);
| ^ invalid argument name in format string
@ -33,7 +31,7 @@ LL | let _ = format!("{_}", _ = 6usize);
= note: argument names cannot start with an underscore
error: invalid format string: expected `'}'` but string was terminated
--> $DIR/format-string-error.rs:19:23
--> $DIR/format-string-error.rs:21:23
|
LL | let _ = format!("{");
| ^ expected `'}'` in format string
@ -41,7 +39,7 @@ LL | let _ = format!("{");
= note: if you intended to print `{`, you can escape it using `{{`
error: invalid format string: unmatched `}` found
--> $DIR/format-string-error.rs:21:22
--> $DIR/format-string-error.rs:23:22
|
LL | let _ = format!("}");
| ^ unmatched `}` in format string
@ -49,7 +47,7 @@ LL | let _ = format!("}");
= note: if you intended to print `}`, you can escape it using `}}`
error: invalid format string: expected `'}'`, found `'/'`
--> $DIR/format-string-error.rs:23:23
--> $DIR/format-string-error.rs:25:23
|
LL | let _ = format!("{/}");
| ^ expected `}` in format string

5
src/test/ui/macros/bad_hello.rs
View File

@ -9,5 +9,8 @@
// except according to those terms.
fn main() {
println!(3 + 4); //~ ERROR expected a literal
println!(3 + 4);
//~^ ERROR format argument must be a string literal
println!(3, 4);
//~^ ERROR format argument must be a string literal
}

20
src/test/ui/macros/bad_hello.stderr
View File

@ -1,12 +1,22 @@
error: expected a literal
error: format argument must be a string literal
--> $DIR/bad_hello.rs:12:14
|
LL | println!(3 + 4); //~ ERROR expected a literal
LL | println!(3 + 4);
| ^^^^^
help: you might be missing a string literal to format with
|
LL | println!("{}", 3 + 4); //~ ERROR expected a literal
| ^^^^^^^^^^^
LL | println!("{}", 3 + 4);
| ^^^^^
error: aborting due to previous error
error: format argument must be a string literal
--> $DIR/bad_hello.rs:14:14
|
LL | println!(3, 4);
| ^
help: you might be missing a string literal to format with
|
LL | println!("{}, {}", 3, 4);
| ^^^^^^^^^
error: aborting due to 2 previous errors

5
src/test/ui/macros/format-foreign.stderr
View File

@ -2,12 +2,13 @@ error: multiple unused formatting arguments
--> $DIR/format-foreign.rs:12:30
|
LL | println!("%.*3$s %s!/n", "Hello,", "World", 4); //~ ERROR multiple unused formatting arguments
| -------------------------^^^^^^^^--^^^^^^^--^-- multiple unused arguments in this statement
| -------------- ^^^^^^^^ ^^^^^^^ ^
| |
| multiple missing formatting arguments
|
= help: `%.*3$s` should be written as `{:.2$}`
= help: `%s` should be written as `{}`
= note: printf formatting not supported; see the documentation for `std::fmt`
= 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: argument never used
--> $DIR/format-foreign.rs:13:29

43
src/test/ui/macros/format-unused-lables.stderr
View File

@ -2,24 +2,21 @@ error: multiple unused formatting arguments
--> $DIR/format-unused-lables.rs:12:22
|
LL | println!("Test", 123, 456, 789);
| -----------------^^^--^^^--^^^-- multiple unused arguments in this statement
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
| ------ ^^^ ^^^ ^^^
| |
| multiple missing formatting arguments
error: multiple unused formatting arguments
--> $DIR/format-unused-lables.rs:16:9
|
LL | / println!("Test2",
LL | | 123, //~ ERROR multiple unused formatting arguments
| | ^^^
LL | | 456,
| | ^^^
LL | | 789
| | ^^^
LL | | );
| |______- multiple unused arguments in this statement
|
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
LL | println!("Test2",
| ------- multiple missing formatting arguments
LL | 123, //~ ERROR multiple unused formatting arguments
| ^^^
LL | 456,
| ^^^
LL | 789
| ^^^
error: named argument never used
--> $DIR/format-unused-lables.rs:21:35
@ -30,18 +27,18 @@ LL | println!("Some stuff", UNUSED="args"); //~ ERROR named argument never u
error: multiple unused formatting arguments
--> $DIR/format-unused-lables.rs:24:9
|
LL | / println!("Some more $STUFF",
LL | | "woo!", //~ ERROR multiple unused formatting arguments
| | ^^^^^^
LL | | STUFF=
LL | | "things"
| | ^^^^^^^^
LL | | , UNUSED="args");
| |_______________________^^^^^^_- multiple unused arguments in this statement
LL | println!("Some more $STUFF",
| ------------------ multiple missing formatting arguments
LL | "woo!", //~ ERROR multiple unused formatting arguments
| ^^^^^^
LL | STUFF=
LL | "things"
| ^^^^^^^^
LL | , UNUSED="args");
| ^^^^^^
|
= help: `$STUFF` should be written as `{STUFF}`
= note: shell formatting not supported; see the documentation for `std::fmt`
= 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: aborting due to 4 previous errors

9
src/test/ui/macros/trace-macro.stderr
View File

@ -5,8 +5,9 @@ LL | println!("Hello, World!");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: expanding `println! { "Hello, World!" }`
= note: to `print ! ( concat ! ( "Hello, World!" , "/n" ) )`
= note: expanding `print! { concat ! ( "Hello, World!" , "/n" ) }`
= note: to `$crate :: io :: _print ( format_args ! ( concat ! ( "Hello, World!" , "/n" ) )
)`
= note: to `{ print ! ( "Hello, World!" ) ; print ! ( "/n" ) ; }`
= note: expanding `print! { "Hello, World!" }`
= note: to `$crate :: io :: _print ( format_args ! ( "Hello, World!" ) )`
= note: expanding `print! { "/n" }`
= note: to `$crate :: io :: _print ( format_args ! ( "/n" ) )`