Don't add "in this macro invocation" label to desugared spans

src/librustc_errors/emitter.rs

@@ -767,6 +767,7 @@ fn fix_multispan_in_std_macros(&mut self,
                         }
                         // Check to make sure we're not in any <*macros>
                         if !cm.span_to_filename(def_site).is_macros() &&
+                           !trace.macro_decl_name.starts_with("desugaring of ") &&
                            !trace.macro_decl_name.starts_with("#[") ||
                            always_backtrace {
                             new_labels.push((trace.call_site,

src/test/ui/const-fn-error.stderr

@@ -17,16 +17,12 @@ error[E0015]: calls in constant functions are limited to constant functions, str
    |
 17 |     for i in 0..x { //~ ERROR calls in constant functions
    |              ^^^^
-   |              |
-   |              in this macro invocation
 
 error[E0019]: constant function contains unimplemented expression type
   --> $DIR/const-fn-error.rs:17:14
    |
 17 |     for i in 0..x { //~ ERROR calls in constant functions
    |              ^^^^
-   |              |
-   |              in this macro invocation
 
 error[E0080]: constant evaluation error
   --> $DIR/const-fn-error.rs:21:5

src/test/ui/suggestions/try-on-option.stderr

@@ -10,10 +10,7 @@ error[E0277]: the `?` operator can only be used in a function that returns `Resu
   --> $DIR/try-on-option.rs:23:5
    |
 23 |     x?; //~ the `?` operator
-   |     --
-   |     |
-   |     cannot use the `?` operator in a function that returns `u32`
-   |     in this macro invocation
+   |     ^^ cannot use the `?` operator in a function that returns `u32`
    |
    = help: the trait `std::ops::Try` is not implemented for `u32`
    = note: required by `std::ops::Try::from_error`

src/test/ui/suggestions/try-operator-on-main.stderr

@@ -2,10 +2,7 @@ error[E0277]: the `?` operator can only be used in a function that returns `Resu
   --> $DIR/try-operator-on-main.rs:19:5
    |
 19 |     std::fs::File::open("foo")?; //~ ERROR the `?` operator can only
-   |     ---------------------------
-   |     |
-   |     cannot use the `?` operator in a function that returns `()`
-   |     in this macro invocation
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot use the `?` operator in a function that returns `()`
    |
    = help: the trait `std::ops::Try` is not implemented for `()`
    = note: required by `std::ops::Try::from_error`
@@ -14,10 +11,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `std
   --> $DIR/try-operator-on-main.rs:22:5
    |
 22 |     ()?; //~ ERROR the `?` operator can only
-   |     ---
-   |     |
-   |     the `?` operator cannot be applied to type `()`
-   |     in this macro invocation
+   |     ^^^ the `?` operator cannot be applied to type `()`
    |
    = help: the trait `std::ops::Try` is not implemented for `()`
    = note: required by `std::ops::Try::into_result`
@@ -38,10 +32,7 @@ error[E0277]: the `?` operator can only be applied to values that implement `std
   --> $DIR/try-operator-on-main.rs:32:5
    |
 32 |     ()?; //~ ERROR the `?` operator can only
-   |     ---
-   |     |
-   |     the `?` operator cannot be applied to type `()`
-   |     in this macro invocation
+   |     ^^^ the `?` operator cannot be applied to type `()`
    |
    = help: the trait `std::ops::Try` is not implemented for `()`
    = note: required by `std::ops::Try::into_result`