Reduce verbosity of errors involving builtin macros

Do not show note "this error originates in" when it is caused by one in
an explicit block list of builtin macros. Most notably, `println!` and
friends will stop doing so.

Author: estebank

compiler/rustc_errors/src/emitter.rs

@@ -333,7 +333,9 @@ pub trait Emitter: Translate {
                     // are some which do actually involve macros.
                     ExpnKind::Inlined | ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
 
-                    ExpnKind::Macro(macro_kind, name) => Some((macro_kind, name)),
+                    ExpnKind::Macro(macro_kind, name) => {
+                        Some((macro_kind, name, expn_data.builtin_name))
+                    }
                 }
             })
             .collect();
@@ -345,9 +347,9 @@ pub trait Emitter: Translate {
         self.render_multispans_macro_backtrace(span, children, backtrace);
 
         if !backtrace {
-            if let Some((macro_kind, name)) = has_macro_spans.first() {
+            if let Some((macro_kind, name, builtin_name)) = has_macro_spans.first() {
                 // Mark the actual macro this originates from
-                let and_then = if let Some((macro_kind, last_name)) = has_macro_spans.last()
+                let and_then = if let Some((macro_kind, last_name, _)) = has_macro_spans.last()
                     && last_name != name
                 {
                     let descr = macro_kind.descr();
@@ -364,12 +366,25 @@ pub trait Emitter: Translate {
                     (in Nightly builds, run with -Z macro-backtrace for more info)",
                 );
 
-                children.push(SubDiagnostic {
-                    level: Level::Note,
-                    message: vec![(DiagnosticMessage::Str(msg), Style::NoStyle)],
-                    span: MultiSpan::new(),
-                    render_span: None,
-                });
+                if let Some(
+                    "assert" | "bench" | "cfg" | "concat" | "concat_idents" | "env" | "format_args"
+                    | "format_args_nl" | "global_allocator" | "include_str" | "test",
+                ) = builtin_name.as_ref().map(|n| n.as_str())
+                {
+                    // We explicitly ignore these builtin macros and not show the line, as end
+                    // users will never care about these, the macros should be providing good
+                    // diagnostics always.
+                    // FIXME: we could include the builtin `derive` macros here, but we need to
+                    // audit every one of them before doing so to verify that they always produce
+                    // reasonable diagnostics that point at the macro use.
+                } else {
+                    children.push(SubDiagnostic {
+                        level: Level::Note,
+                        message: vec![(DiagnosticMessage::Str(msg), Style::NoStyle)],
+                        span: MultiSpan::new(),
+                        render_span: None,
+                    });
+                }
             }
         }
     }

compiler/rustc_expand/src/base.rs

@@ -858,6 +858,7 @@ impl SyntaxExtension {
         descr: Symbol,
         macro_def_id: Option<DefId>,
         parent_module: Option<DefId>,
+        builtin_name: Option<Symbol>,
     ) -> ExpnData {
         ExpnData::new(
             ExpnKind::Macro(self.macro_kind(), descr),
@@ -871,6 +872,7 @@ impl SyntaxExtension {
             self.allow_internal_unsafe,
             self.local_inner_macros,
             self.collapse_debuginfo,
+            builtin_name,
         )
     }
 }

compiler/rustc_resolve/src/macros.rs

@@ -292,6 +292,7 @@ impl<'a> ResolverExpand for Resolver<'a> {
                 fast_print_path(path),
                 def_id,
                 def_id.map(|def_id| self.macro_def_scope(def_id).nearest_parent_mod()),
+                ext.builtin_name,
             ),
             self.create_stable_hashing_context(),
         );

compiler/rustc_span/src/hygiene.rs

@@ -961,6 +961,9 @@ pub struct ExpnData {
     /// Should debuginfo for the macro be collapsed to the outermost expansion site (in other
     /// words, was the macro definition annotated with `#[collapse_debuginfo]`)?
     pub collapse_debuginfo: bool,
+    /// If this expansion comes from a builtin macro, this is the macro's name. Used when emitting
+    /// diagnostics to hide the line "this error originates in...".
+    pub builtin_name: Option<Symbol>,
 }
 
 impl !PartialEq for ExpnData {}
@@ -979,6 +982,7 @@ impl ExpnData {
         allow_internal_unsafe: bool,
         local_inner_macros: bool,
         collapse_debuginfo: bool,
+        builtin_name: Option<Symbol>,
     ) -> ExpnData {
         ExpnData {
             kind,
@@ -993,6 +997,7 @@ impl ExpnData {
             allow_internal_unsafe,
             local_inner_macros,
             collapse_debuginfo,
+            builtin_name,
         }
     }
 
@@ -1017,6 +1022,7 @@ impl ExpnData {
             allow_internal_unsafe: false,
             local_inner_macros: false,
             collapse_debuginfo: false,
+            builtin_name: None,
         }
     }
 

src/test/ui/allocator/not-an-allocator.stderr

@@ -7,7 +7,6 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
-   = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
   --> $DIR/not-an-allocator.rs:2:11
@@ -18,7 +17,6 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
-   = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
   --> $DIR/not-an-allocator.rs:2:11
@@ -29,7 +27,6 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
-   = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
   --> $DIR/not-an-allocator.rs:2:11
@@ -40,7 +37,6 @@ LL | static A: usize = 0;
    |           ^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
    = help: the trait `GlobalAlloc` is implemented for `System`
-   = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors
 

src/test/ui/allocator/two-allocators.stderr

@@ -7,8 +7,6 @@ LL | #[global_allocator]
    | ------------------- in this procedural macro expansion
 LL | static B: System = System;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot define a new global allocator
-   |
-   = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/attributes/extented-attribute-macro-error.stderr

@@ -3,8 +3,6 @@ error: couldn't read the file
    |
 LL | #![doc = include_str!("../not_existing_file.md")]
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `include_str` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-and-init.stderr

@@ -8,8 +8,6 @@ LL |     println!("{}", false && { i = 5; true });
    |                               ----- binding initialized here in some conditions
 LL |     println!("{}", i);
    |                    ^ `i` used here but it is possibly-uninitialized
-   |
-   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-break-uninit-2.stderr

@@ -7,7 +7,6 @@ LL |     let x: isize;
 LL |     println!("{}", x);
    |                    ^ `x` used here but it isn't initialized
    |
-   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider assigning a value
    |
 LL |     let x: isize = 0;

src/test/ui/borrowck/borrowck-break-uninit.stderr

@@ -7,7 +7,6 @@ LL |     let x: isize;
 LL |     println!("{}", x);
    |                    ^ `x` used here but it isn't initialized
    |
-   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider assigning a value
    |
 LL |     let x: isize = 0;