Auto merge of #43533 - nrc:macro-save, r=jseyfried,

Three small fixes for save-analysis

First commit does some naive deduplication of macro uses. We end up with lots of duplication here because of the weird way we get this data (we extract a use for every span generated by a macro use).

Second commit is basically a typo fix.

Third commit is a bit interesting, it partially reverts a change from #40939 where temporary variables in format! (and thus println!) got a span with the primary pointing at the value stored into the temporary (e.g., `x` in `println!("...", x)`). If `format!` had a definition it should point at the temporary in the macro def, but since it is built-in, that is not possible (for now), so `DUMMY_SP` is the best we can do (using the span in the callee really breaks save-analysis because it thinks `x` is a definition as well as a reference).

There aren't a test for this stuff because: the deduplication is filtered by any of the users of save-analysis, so it is purely an efficiency change. I couldn't actually find an example for the second commit that we have any machinery to test, and the third commit is tested by the RLS, so there will be a test once I update the RLS version and and uncomment the previously failing tests).

r? @jseyfried

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 7351377e771..9734bb867f1 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -20,7 +20,7 @@ use syntax::ext::build::AstBuilder;
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax::symbol::{Symbol, keywords};
-use syntax_pos::Span;
+use syntax_pos::{Span, DUMMY_SP};
 use syntax::tokenstream;
 
 use std::collections::{HashMap, HashSet};
@@ -558,8 +558,10 @@ impl<'a, 'b> Context<'a, 'b> {
         // passed to this function.
         for (i, e) in self.args.into_iter().enumerate() {
             let name = self.ecx.ident_of(&format!("__arg{}", i));
-            let span =
-                Span { ctxt: e.span.ctxt.apply_mark(self.ecx.current_expansion.mark), ..e.span };
+            let span = Span {
+                ctxt: e.span.ctxt.apply_mark(self.ecx.current_expansion.mark),
+                ..DUMMY_SP
+            };
             pats.push(self.ecx.pat_ident(span, name));
             for ref arg_ty in self.arg_unique_types[i].iter() {
                 locals.push(Context::format_arg(self.ecx, self.macsp, e.span, arg_ty, name));