Fix duplicate help on export_name and others

Signed-off-by: Jonathan Brouwer <jonathantbrouwer@gmail.com>

Author: JonathanBrouwer

compiler/rustc_attr_parsing/src/session_diagnostics.rs

@@ -566,10 +566,7 @@ impl<'a, G: EmissionGuarantee> Diagnostic<'a, G> for AttributeParseError {
                 diag.code(E0565);
             }
             AttributeParseErrorReason::ExpectedNameValue(None) => {
-                diag.span_label(
-                    self.span,
-                    format!("expected this to be of the form `{name} = \"...\"`"),
-                );
+                // The suggestion we add below this match already contains enough information
             }
             AttributeParseErrorReason::ExpectedNameValue(Some(name)) => {
                 diag.span_label(

tests/ui/attributes/malformed-attrs.stderr

@@ -374,10 +374,7 @@ error[E0539]: malformed `export_name` attribute input
   --> $DIR/malformed-attrs.rs:32:1
    |
 LL | #[unsafe(export_name)]
-   | ^^^^^^^^^^^^^^^^^^^^^^
-   | |
-   | expected this to be of the form `export_name = "..."`
-   | help: must be of the form: `#[export_name = "name"]`
+   | ^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[export_name = "name"]`
 
 error: `rustc_allow_const_fn_unstable` expects a list of feature names
   --> $DIR/malformed-attrs.rs:34:1
@@ -424,10 +421,7 @@ error[E0539]: malformed `rustc_macro_transparency` attribute input
   --> $DIR/malformed-attrs.rs:45:1
    |
 LL | #[rustc_macro_transparency]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   | |
-   | expected this to be of the form `rustc_macro_transparency = "..."`
-   | help: must be of the form: `#[rustc_macro_transparency = "transparent|semitransparent|opaque"]`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[rustc_macro_transparency = "transparent|semitransparent|opaque"]`
 
 error[E0539]: malformed `repr` attribute input
   --> $DIR/malformed-attrs.rs:47:1
@@ -511,10 +505,7 @@ error[E0539]: malformed `export_name` attribute input
   --> $DIR/malformed-attrs.rs:68:1
    |
 LL | #[export_name()]
-   | ^^^^^^^^^^^^^^^^
-   | |
-   | expected this to be of the form `export_name = "..."`
-   | help: must be of the form: `#[export_name = "name"]`
+   | ^^^^^^^^^^^^^^^^ help: must be of the form: `#[export_name = "name"]`
 
 error[E0805]: malformed `used` attribute input
   --> $DIR/malformed-attrs.rs:70:1