Modify invalid macro in expression context diagnostic

Author: estebank

src/libsyntax/ext/expand.rs

@@ -1036,10 +1036,26 @@ impl<'a> Parser<'a> {
             // Avoid emitting backtrace info twice.
             let def_site_span = self.span.with_ctxt(SyntaxContext::empty());
             let mut err = self.diagnostic().struct_span_err(def_site_span, &msg);
-            let msg = format!("caused by the macro expansion here; the usage \
-                               of `{}!` is likely invalid in {} context",
-                               macro_path, kind_name);
-            err.span_note(span, &msg).emit();
+            err.span_label(span, "caused by the macro expansion here");
+            let msg = format!(
+                "the usage of `{}!` is likely invalid in {} context",
+                macro_path,
+                kind_name,
+            );
+            err.note(&msg);
+            let semi_span = self.sess.source_map().next_point(span);
+            match self.sess.source_map().span_to_snippet(semi_span) {
+                Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
+                    err.span_suggestion_with_applicability(
+                        semi_span,
+                        "you might be missing a semicolon here",
+                        ";".to_owned(),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+                _ => {}
+            }
+            err.emit();
         }
     }
 }

src/test/ui/issues/issue-30007.stderr

@@ -3,12 +3,11 @@ error: macro expansion ignores token `;` and any following
    |
 LL |     () => ( String ; );     //~ ERROR macro expansion ignores token `;`
    |                    ^
-   |
-note: caused by the macro expansion here; the usage of `t!` is likely invalid in type context
-  --> $DIR/issue-30007.rs:16:16
-   |
+...
 LL |     let i: Vec<t!()>;
-   |                ^^^^
+   |                ---- caused by the macro expansion here
+   |
+   = note: the usage of `t!` is likely invalid in type context
 
 error: aborting due to previous error
 

src/test/ui/macros/macro-context.stderr

@@ -3,36 +3,35 @@ error: macro expansion ignores token `;` and any following
    |
 LL |     () => ( i ; typeof );   //~ ERROR expected expression, found reserved keyword `typeof`
    |               ^
-   |
-note: caused by the macro expansion here; the usage of `m!` is likely invalid in type context
-  --> $DIR/macro-context.rs:20:12
-   |
+...
 LL |     let a: m!();
-   |            ^^^^
+   |            ---- caused by the macro expansion here
+   |
+   = note: the usage of `m!` is likely invalid in type context
 
 error: macro expansion ignores token `typeof` and any following
   --> $DIR/macro-context.rs:13:17
    |
 LL |     () => ( i ; typeof );   //~ ERROR expected expression, found reserved keyword `typeof`
    |                 ^^^^^^
-   |
-note: caused by the macro expansion here; the usage of `m!` is likely invalid in expression context
-  --> $DIR/macro-context.rs:21:13
-   |
+...
 LL |     let i = m!();
-   |             ^^^^
+   |             ----- help: you might be missing a semicolon here: `;`
+   |             |
+   |             caused by the macro expansion here
+   |
+   = note: the usage of `m!` is likely invalid in expression context
 
 error: macro expansion ignores token `;` and any following
   --> $DIR/macro-context.rs:13:15
    |
 LL |     () => ( i ; typeof );   //~ ERROR expected expression, found reserved keyword `typeof`
    |               ^
-   |
-note: caused by the macro expansion here; the usage of `m!` is likely invalid in pattern context
-  --> $DIR/macro-context.rs:23:9
-   |
+...
 LL |         m!() => {}
-   |         ^^^^
+   |         ---- caused by the macro expansion here
+   |
+   = note: the usage of `m!` is likely invalid in pattern context
 
 error: expected expression, found reserved keyword `typeof`
   --> $DIR/macro-context.rs:13:17

src/test/ui/macros/macro-in-expression-context.fixed

@@ -0,0 +1,15 @@
+// run-rustfix
+
+macro_rules! foo {
+    () => {
+        assert_eq!("A", "A");
+        assert_eq!("B", "B");
+    }
+    //~^^ ERROR macro expansion ignores token `assert_eq` and any following
+    //~| NOTE the usage of `foo!` is likely invalid in expression context
+}
+
+fn main() {
+    foo!();
+    //~^ NOTE caused by the macro expansion here
+}

src/test/ui/macros/macro-in-expression-context.rs

@@ -0,0 +1,15 @@
+// run-rustfix
+
+macro_rules! foo {
+    () => {
+        assert_eq!("A", "A");
+        assert_eq!("B", "B");
+    }
+    //~^^ ERROR macro expansion ignores token `assert_eq` and any following
+    //~| NOTE the usage of `foo!` is likely invalid in expression context
+}
+
+fn main() {
+    foo!()
+    //~^ NOTE caused by the macro expansion here
+}

src/test/ui/macros/macro-in-expression-context.stderr

@@ -0,0 +1,15 @@
+error: macro expansion ignores token `assert_eq` and any following
+  --> $DIR/macro-in-expression-context.rs:6:9
+   |
+LL |         assert_eq!("B", "B");
+   |         ^^^^^^^^^
+...
+LL |     foo!()
+   |     ------- help: you might be missing a semicolon here: `;`
+   |     |
+   |     caused by the macro expansion here
+   |
+   = note: the usage of `foo!` is likely invalid in expression context
+
+error: aborting due to previous error
+

src/test/ui/parser/macro/macro-incomplete-parse.stderr

@@ -3,12 +3,11 @@ error: macro expansion ignores token `,` and any following
    |
 LL |         , //~ ERROR macro expansion ignores token `,`
    |         ^
-   |
-note: caused by the macro expansion here; the usage of `ignored_item!` is likely invalid in item context
-  --> $DIR/macro-incomplete-parse.rs:31:1
-   |
+...
 LL | ignored_item!();
-   | ^^^^^^^^^^^^^^^^
+   | ---------------- caused by the macro expansion here
+   |
+   = note: the usage of `ignored_item!` is likely invalid in item context
 
 error: expected one of `.`, `;`, `?`, `}`, or an operator, found `,`
   --> $DIR/macro-incomplete-parse.rs:22:14
@@ -24,12 +23,11 @@ error: macro expansion ignores token `,` and any following
    |
 LL |     () => ( 1, 2 ) //~ ERROR macro expansion ignores token `,`
    |              ^
-   |
-note: caused by the macro expansion here; the usage of `ignored_pat!` is likely invalid in pattern context
-  --> $DIR/macro-incomplete-parse.rs:36:9
-   |
+...
 LL |         ignored_pat!() => (),
-   |         ^^^^^^^^^^^^^^
+   |         -------------- caused by the macro expansion here
+   |
+   = note: the usage of `ignored_pat!` is likely invalid in pattern context
 
 error: aborting due to 3 previous errors