Propagate macro backtraces more often, improve formatting diagnostics #24003
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r? @pcwalton (rust_highfive has picked a reviewer for you, use r? to override) |
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It occurs to me that #23459 actually had a much better motivating example than |
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Great! Could you add some tests for these? E.g. for the macro_rules! foo { //~ NODE in expansion of
() => {
1.fake(); //~ ERROR does not implement any method
}
}
fn main() {
foo!(); //~ NOTE expansion site
}Similarly one could have |
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Yes, I can add some tests. |
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I added new tests:
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I've noticed that the backtraces introduced with this PR can appear repeatedly: The second two backtraces are obnoxious. I suspect the fix is for I'm also wondering about the first Also: |
I agree.
We haven't been very good about using |
src/libsyntax/diagnostic.rs
Outdated
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Hm, could you add a brief comment about this?
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There's some code a few lines up doing the same sort of sp.expn_id to COMMAND_LINE_EXPN comparison:
// We cannot check equality directly with COMMAND_LINE_SP
// since PartialEq is manually implemented to ignore the ExpnId
let ss = if sp.expn_id == COMMAND_LINE_EXPN {
...
I'll factor out the sp.expn_id == COMMAND_LINE_EXPN to a local variable and put the comment there.
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Looks good, r=me with one little comment. |
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☔ The latest upstream changes (presumably #23857) made this pull request unmergeable. Please resolve the merge conflicts. |
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There seems to be a general problem where we don't output macro backtraces until after the expansion phase. The macro_rules! format_template {
($tmp:tt) => (format!($tmp, a=123, b=456))
}
fn main() {
format_template!("{a}{b}");
format_template!("{a}");
format_template!("{a}{b}");
format_template!("{a}");
} |
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@huonw I rebased my changes, factored out a |
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☔ The latest upstream changes (presumably #24328) made this pull request unmergeable. Please resolve the merge conflicts. |
* In noop_fold_expr, call new_span in these cases:
- ExprMethodCall's identifier
- ExprField's identifier
- ExprTupField's integer
Calling new_span for ExprMethodCall's identifier is necessary to print
an acceptable diagnostic for write!(&2, ""). We see this error:
<std macros>:2:20: 2:66 error: type `&mut _` does not implement any method in scope named `write_fmt`
<std macros>:2 ( & mut * $ dst ) . write_fmt ( format_args ! ( $ ( $ arg ) * ) ) )
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With this change, we also see a macro expansion backtrace leading to
the write!(&2, "") call site.
* After fully expanding a macro, we replace the expansion expression's
span with the original span. Call fld.new_span to add a backtrace to
this span. (Note that I'm call new_span after bt.pop(), so the macro
just expanded isn't on the backtrace.)
The motivating example for this change is println!("{}"). The format
string literal is concat!($fmt, "arg") and is inside the libstd macro.
We need to see the backtrace to find the println! call site.
* Add a backtrace to the format_args! format expression span.
Addresses rust-lang#23459
It was added in 2011-08-05 and reduced to a no-op ten days later.
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@huonw I rebased my PR to account for @nikomatsakis's diagnostic improvements. I rewrote the |
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@bors r+ |
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📌 Commit ddbdf51 has been approved by |
* In `noop_fold_expr`, call `new_span` in these cases:
- `ExprMethodCall`'s identifier
- `ExprField`'s identifier
- `ExprTupField`'s integer
Calling `new_span` for `ExprMethodCall`'s identifier is necessary to print
an acceptable diagnostic for `write!(&2, "")`. We see this error:
```
<std macros>:2:20: 2:66 error: type `&mut _` does not implement any method in scope named `write_fmt`
<std macros>:2 ( & mut * $ dst ) . write_fmt ( format_args ! ( $ ( $ arg ) * ) ) )
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
With this change, we also see a macro expansion backtrace leading to
the `write!(&2, "")` call site.
* After fully expanding a macro, we replace the expansion expression's
span with the original span. Call `fld.new_span` to add a backtrace to
this span. (Note that I'm call `new_span` after `bt.pop()`, so the macro
just expanded isn't on the backtrace.)
The motivating example for this change is `println!("{}")`. The format
string literal is `concat!($fmt, "arg")` and is inside the libstd macro.
We need to see the backtrace to find the `println!` call site.
* Add a backtrace to the `format_args!` format expression span.
r? alexcrichton
Addresses #23459
5 participants
In
noop_fold_expr, callnew_spanin these cases:ExprMethodCall's identifierExprField's identifierExprTupField's integerCalling
new_spanforExprMethodCall's identifier is necessary to printan acceptable diagnostic for
write!(&2, ""). We see this error:With this change, we also see a macro expansion backtrace leading to
the
write!(&2, "")call site.After fully expanding a macro, we replace the expansion expression's
span with the original span. Call
fld.new_spanto add a backtrace tothis span. (Note that I'm call
new_spanafterbt.pop(), so the macrojust expanded isn't on the backtrace.)
The motivating example for this change is
println!("{}"). The formatstring literal is
concat!($fmt, "arg")and is inside the libstd macro.We need to see the backtrace to find the
println!call site.Add a backtrace to the
format_args!format expression span.r? alexcrichton
Addresses #23459