Do not show in this macro invocation for compiler desugared spans

Author: sinkuu

src/librustc_errors/emitter.rs

@@ -677,7 +677,8 @@ impl EmitterWriter {
                         }
                         // Check to make sure we're not in any <*macros>
                         if !cm.span_to_filename(def_site).contains("macros>") &&
-                           !trace.macro_decl_name.starts_with("#[") {
+                           !trace.macro_decl_name.starts_with("#[") &&
+                           !trace.macro_decl_name.starts_with("desugaring of") {
                             new_labels.push((trace.call_site,
                                              "in this macro invocation".to_string()));
                             break;

src/test/compile-fail/E0297.rs

@@ -14,4 +14,5 @@ fn main() {
     for Some(x) in xs {}
     //~^ ERROR E0297
     //~| NOTE pattern `None` not covered
+    //~| NOTE in this expansion of desugaring of `for`
 }

src/test/compile-fail/if-let-arm-types.rs

@@ -13,6 +13,8 @@ fn main() {
         //~^ expected (), found integral variable
         //~| expected type `()`
         //~| found type `{integer}`
+        //~| NOTE: in this expansion of desugaring of `if let`
+        //~| NOTE: in this expansion of desugaring of `if let`
         ()
     } else {                //~ NOTE: `if let` arm with an incompatible type
         1

src/test/ui/compiler_desugaring.rs

@@ -0,0 +1,26 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// checks that errors on compiler-desugared spans don't have
+// useless `in this macro invocation` notes.
+
+fn main() {
+    let _ = foo();
+}
+
+fn foo() -> Result<(), ()> {
+    let _: i32 = bar()?; //~ ERROR E0308
+    Ok(())
+}
+
+fn bar() -> Result<(), ()> {
+    Ok(())
+}
+

src/test/ui/compiler_desugaring.stderr

@@ -0,0 +1,16 @@
+error[E0308]: match arms have incompatible types
+  --> $DIR/compiler_desugaring.rs:19:18
+   |
+19 |     let _: i32 = bar()?; //~ ERROR E0308
+   |                  ^^^^^^ expected i32, found ()
+   |
+   = note: expected type `i32`
+              found type `()`
+note: match arm with an incompatible type
+  --> $DIR/compiler_desugaring.rs:19:18
+   |
+19 |     let _: i32 = bar()?; //~ ERROR E0308
+   |                  ^^^^^^
+
+error: aborting due to previous error
+