1 files changed, 49 insertions, 0 deletions
diff --git a/src/test/ui/proc-macro/auxiliary/three-equals.rs b/src/test/ui/proc-macro/auxiliary/three-equals.rs
new file mode 100644
index 000000000..e740e86e5
--- /dev/null
+++ b/src/test/ui/proc-macro/auxiliary/three-equals.rs
@@ -0,0 +1,49 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro_diagnostic, proc_macro_span, proc_macro_def_site)]
+
+extern crate proc_macro;
+
+use proc_macro::{TokenStream, TokenTree, Span, Diagnostic};
+
+fn parse(input: TokenStream) -> Result<(), Diagnostic> {
+    let mut count = 0;
+    let mut last_span = Span::def_site();
+    for tree in input {
+        let span = tree.span();
+        if count >= 3 {
+            return Err(span.error(format!("expected EOF, found `{}`.", tree))
+                           .span_note(last_span, "last good input was here")
+                           .help("input must be: `===`"))
+        }
+
+        if let TokenTree::Punct(ref tt) = tree {
+            if tt.as_char() == '=' {
+                count += 1;
+                last_span = span;
+                continue
+            }
+        }
+        return Err(span.error(format!("expected `=`, found `{}`.", tree)));
+    }
+
+    if count < 3 {
+        return Err(Span::def_site()
+                       .error(format!("found {} equal signs, need exactly 3", count))
+                       .help("input must be: `===`"))
+    }
+
+    Ok(())
+}
+
+#[proc_macro]
+pub fn three_equals(input: TokenStream) -> TokenStream {
+    if let Err(diag) = parse(input) {
+        diag.emit();
+        return TokenStream::new();
+    }
+
+    "3".parse().unwrap()
+}