Rollup merge of #44088 - bjorn3:better_trace_macros, r=jseyfried

Fix "new trace_macros doesn't work if there's an error during expansion"

Fixes #43493

3 files changed, 20 insertions, 3 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index cac2ff975d6..c139cfeaebf 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -792,7 +792,7 @@ impl<'a> ExtCtxt<'a> {
     pub fn span_bug(&self, sp: Span, msg: &str) -> ! {
         self.parse_sess.span_diagnostic.span_bug(sp, msg);
     }
-    pub fn trace_macros_diag(&self) {
+    pub fn trace_macros_diag(&mut self) {
         for (sp, notes) in self.expansions.iter() {
             let mut db = self.parse_sess.span_diagnostic.span_note_diag(*sp, "trace_macro");
             for note in notes {
@@ -800,6 +800,8 @@ impl<'a> ExtCtxt<'a> {
             }
             db.emit();
         }
+        // Fixme: does this result in errors?
+        self.expansions.clear();
     }
     pub fn bug(&self, msg: &str) -> ! {
         self.parse_sess.span_diagnostic.bug(msg);
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 2f7d5685b6e..de9c085cc78 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -384,13 +384,14 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         if self.cx.current_expansion.depth > self.cx.ecfg.recursion_limit {
             let info = self.cx.current_expansion.mark.expn_info().unwrap();
             let suggested_limit = self.cx.ecfg.recursion_limit * 2;
-            let mut err = self.cx.struct_span_fatal(info.call_site,
+            let mut err = self.cx.struct_span_err(info.call_site,
                 &format!("recursion limit reached while expanding the macro `{}`",
                          info.callee.name()));
             err.help(&format!(
                 "consider adding a `#![recursion_limit=\"{}\"]` attribute to your crate",
                 suggested_limit));
             err.emit();
+            self.cx.trace_macros_diag();
             panic!(FatalError);
         }
 
@@ -439,11 +440,13 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             }
             ProcMacroDerive(..) | BuiltinDerive(..) => {
                 self.cx.span_err(attr.span, &format!("`{}` is a derive mode", attr.path));
+                self.cx.trace_macros_diag();
                 kind.dummy(attr.span)
             }
             _ => {
                 let msg = &format!("macro `{}` may not be used in attributes", attr.path);
                 self.cx.span_err(attr.span, msg);
+                self.cx.trace_macros_diag();
                 kind.dummy(attr.span)
             }
         }
@@ -482,6 +485,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 if let Err(msg) = validate_and_set_expn_info(def_span.map(|(_, s)| s),
                                                              false, false) {
                     self.cx.span_err(path.span, &msg);
+                    self.cx.trace_macros_diag();
                     return kind.dummy(span);
                 }
                 kind.make_from(expand.expand(self.cx, span, mac.node.stream()))
@@ -497,6 +501,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                                                              allow_internal_unstable,
                                                              allow_internal_unsafe) {
                     self.cx.span_err(path.span, &msg);
+                    self.cx.trace_macros_diag();
                     return kind.dummy(span);
                 }
                 kind.make_from(expander.expand(self.cx, span, mac.node.stream()))
@@ -506,6 +511,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 if ident.name == keywords::Invalid.name() {
                     self.cx.span_err(path.span,
                                     &format!("macro {}! expects an ident argument", path));
+                    self.cx.trace_macros_diag();
                     return kind.dummy(span);
                 };
 
@@ -526,11 +532,13 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             MultiDecorator(..) | MultiModifier(..) | AttrProcMacro(..) => {
                 self.cx.span_err(path.span,
                                  &format!("`{}` can only be used in attributes", path));
+                self.cx.trace_macros_diag();
                 return kind.dummy(span);
             }
 
             ProcMacroDerive(..) | BuiltinDerive(..) => {
                 self.cx.span_err(path.span, &format!("`{}` is a derive mode", path));
+                self.cx.trace_macros_diag();
                 return kind.dummy(span);
             }
 
@@ -539,6 +547,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     let msg =
                         format!("macro {}! expects no ident argument, given '{}'", path, ident);
                     self.cx.span_err(path.span, &msg);
+                    self.cx.trace_macros_diag();
                     return kind.dummy(span);
                 }
 
@@ -564,6 +573,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             let msg = format!("non-{kind} macro in {kind} position: {name}",
                               name = path.segments[0].identifier.name, kind = kind.name());
             self.cx.span_err(path.span, &msg);
+            self.cx.trace_macros_diag();
             kind.dummy(span)
         })
     }
@@ -617,6 +627,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             _ => {
                 let msg = &format!("macro `{}` may not be used for derive attributes", attr.path);
                 self.cx.span_err(span, msg);
+                self.cx.trace_macros_diag();
                 kind.dummy(span)
             }
         }
@@ -629,6 +640,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
             Ok(expansion) => expansion,
             Err(mut err) => {
                 err.emit();
+                self.cx.trace_macros_diag();
                 return kind.dummy(span);
             }
         };
@@ -739,6 +751,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         if !traits.is_empty() &&
            (kind == ExpansionKind::TraitItems || kind == ExpansionKind::ImplItems) {
             self.cx.span_err(traits[0].span, "`derive` can be only be applied to items");
+            self.cx.trace_macros_diag();
             return kind.expect_from_annotatables(::std::iter::once(item));
         }
         self.collect(kind, InvocationKind::Attr { attr: attr, traits: traits, item: item })
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 6d58af497f0..5e58f003c2b 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -172,7 +172,9 @@ fn generic_extension<'cx>(cx: &'cx mut ExtCtxt,
     }
 
     let best_fail_msg = parse_failure_msg(best_fail_tok.expect("ran no matchers"));
-    cx.span_fatal(best_fail_spot.substitute_dummy(sp), &best_fail_msg);
+    cx.span_err(best_fail_spot.substitute_dummy(sp), &best_fail_msg);
+    cx.trace_macros_diag();
+    DummyResult::any(sp)
 }
 
 // Note that macro-by-example's input is also matched against a token tree: