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Propagate macro backtraces more often, improve formatting diagnostics

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* 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 #23459
This commit is contained in:
Ryan Prichard
2015-04-03 01:27:04 -07:00
parent 6790b0e519
commit 0f46e4f1f2
3 changed files with 12 additions and 6 deletions
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8
src/libsyntax/fold.rs
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@@ -1176,7 +1176,7 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span}: Expr, folder: &mut T) ->
}
ExprMethodCall(i, tps, args) => {
ExprMethodCall(
respan(i.span, folder.fold_ident(i.node)),
respan(folder.new_span(i.span), folder.fold_ident(i.node)),
tps.move_map(|x| folder.fold_ty(x)),
args.move_map(|x| folder.fold_expr(x)))
}
@@ -1246,11 +1246,13 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span}: Expr, folder: &mut T) ->
}
ExprField(el, ident) => {
ExprField(folder.fold_expr(el),
respan(ident.span, folder.fold_ident(ident.node)))
respan(folder.new_span(ident.span),
folder.fold_ident(ident.node)))
}
ExprTupField(el, ident) => {
ExprTupField(folder.fold_expr(el),
respan(ident.span, folder.fold_usize(ident.node)))
respan(folder.new_span(ident.span),
folder.fold_usize(ident.node)))
}
ExprIndex(el, er) => {
ExprIndex(folder.fold_expr(el), folder.fold_expr(er))