Add module population and case of enum in place of expression

src/librustc_resolve/lib.rs

@@ -2599,13 +2599,14 @@ fn smart_resolve_path_fragment(&mut self,
                         }
                         _ => {}
                     },
-                    (Def::Enum(..), PathSource::TupleStruct) => {
+                    (Def::Enum(..), PathSource::TupleStruct)
+                        | (Def::Enum(..), PathSource::Expr(..))  => {
                         if let Some(variants) = this.collect_enum_variants(def) {
                             err.note(&format!("did you mean to use one \
                                                of the following variants?\n{}",
                                 variants.iter()
-                                    .map(|suggestion| format!("- `{}`",
-                                                              path_names_to_string(suggestion)))
+                                    .map(|suggestion| path_names_to_string(suggestion))
+                                    .map(|suggestion| format!("- `{}`", suggestion))
                                     .collect::<Vec<_>>()
                                     .join("\n")));
 
@@ -3559,6 +3560,8 @@ fn collect_enum_variants(&mut self, enum_def: Def) -> Option<Vec<Path>> {
         }
 
         self.find_module(enum_def).map(|(enum_module, enum_import_suggestion)| {
+            self.populate_module_if_necessary(enum_module);
+
             let mut variants = Vec::new();
             enum_module.for_each_child_stable(|ident, _, name_binding| {
                 if let Def::Variant(..) = name_binding.def() {

src/test/ui/did_you_mean/issue-43871-enum-instead-of-variant.rs

@@ -8,12 +8,20 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+enum Example { Ex(String), NotEx }
+
 fn result_test() {
     let x = Option(1);
 
     if let Option(_) = x {
         println!("It is OK.");
     }
+
+    let y = Example::Ex(String::from("test"));
+
+    if let Example(_) = y {
+        println!("It is OK.");
+    }
 }
 
 fn main() {}

src/test/ui/did_you_mean/issue-43871-enum-instead-of-variant.stderr

 error[E0423]: expected function, found enum `Option`
-  --> $DIR/issue-43871-enum-instead-of-variant.rs:12:13
+  --> $DIR/issue-43871-enum-instead-of-variant.rs:14:13
+   |
+14 |     let x = Option(1);
+   |             ^^^^^^
    |
-12 |     let x = Option(1);
-   |             ^^^^^^ not a function
    = note: did you mean to use one of the following variants?
            - `std::prelude::v1::Option::None`
            - `std::prelude::v1::Option::Some`
 
 error[E0532]: expected tuple struct/variant, found enum `Option`
-  --> $DIR/issue-43871-enum-instead-of-variant.rs:14:12
+  --> $DIR/issue-43871-enum-instead-of-variant.rs:16:12
    |
-14 |     if let Option(_) = x {
+16 |     if let Option(_) = x {
    |            ^^^^^^
    |
    = note: did you mean to use one of the following variants?
            - `std::prelude::v1::Option::None`
            - `std::prelude::v1::Option::Some`
 
-error: aborting due to previous error
+error[E0532]: expected tuple struct/variant, found enum `Example`
+  --> $DIR/issue-43871-enum-instead-of-variant.rs:22:12
+   |
+22 |     if let Example(_) = y {
+   |            ^^^^^^^
+   |
+   = note: did you mean to use one of the following variants?
+           - `Example::Ex`
+           - `Example::NotEx`
+
+error: aborting due to 3 previous errors