Add code to invalid ABI error

src/libsyntax/diagnostic_list.rs

@@ -397,4 +397,5 @@ register_diagnostics! {
     E0630, // rustc_const_unstable attribute must be paired with stable/unstable attribute
     E0693, // incorrect `repr(align)` attribute format
     E0694, // an unknown tool name found in scoped attributes
+    E0697, // invalid ABI
 }

src/libsyntax/parse/parser.rs

@@ -6535,12 +6535,15 @@ impl<'a> Parser<'a> {
                     Some(abi) => Ok(Some(abi)),
                     None => {
                         let prev_span = self.prev_span;
-                        self.span_err(
+                        let mut err = struct_span_err!(
+                            self.sess.span_diagnostic,
                             prev_span,
-                            &format!("invalid ABI: expected one of [{}], \
-                                     found `{}`",
-                                    abi::all_names().join(", "),
-                                    s));
+                            E0697,
+                            "invalid ABI: found `{}`",
+                            s);
+                        err.span_label(prev_span, "invalid ABI");
+                        err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
+                        err.emit();
                         Ok(None)
                     }
                 }

src/test/ui/codemap_tests/unicode.stderr

@@ -1,8 +1,11 @@
-error: invalid ABI: expected one of [cdecl, stdcall, fastcall, vectorcall, thiscall, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, Rust, C, system, rust-intrinsic, rust-call, platform-intrinsic, unadjusted], found `路濫狼á́́`
+error[E0697]: invalid ABI: found `路濫狼á́́`
   --> $DIR/unicode.rs:11:8
    |
 LL | extern "路濫狼á́́" fn foo() {} //~ ERROR invalid ABI
-   |        ^^^^^^^^^
+   |        ^^^^^^^^^ invalid ABI
+   |
+   = help: valid ABIs: cdecl, stdcall, fastcall, vectorcall, thiscall, aapcs, win64, sysv64, ptx-kernel, msp430-interrupt, x86-interrupt, Rust, C, system, rust-intrinsic, rust-call, platform-intrinsic, unadjusted
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0697`.