Suggest using :: instead of . for enums in some cases.

Suggest replacing `.` with `::` when encountering "expected value, found enum":
- in a method-call expression and the method has the same name as a tuple variant
- in a field-access expression and the field has the same name as a unit or tuple variant

2 files changed, 283 insertions, 0 deletions

diff --git a/tests/ui/resolve/enum-expected-value-suggest-variants.rs b/tests/ui/resolve/enum-expected-value-suggest-variants.rs
new file mode 100644
index 00000000000..9f86a0a1ecc
--- /dev/null
+++ b/tests/ui/resolve/enum-expected-value-suggest-variants.rs
@@ -0,0 +1,58 @@
+enum Foo {
+    //~^ HELP consider importing this tuple variant
+    A(u32),
+    B(u32),
+}
+
+enum Bar {
+    C(u32),
+    D(u32),
+    E,
+    F,
+}
+
+fn main() {
+    let _: Foo = Foo(0);
+    //~^ ERROR expected function
+    //~| HELP try to construct one of the enum's variants
+
+    let _: Foo = Foo.A(0);
+    //~^ ERROR expected value, found enum `Foo`
+    //~| HELP use the path separator to refer to a variant
+
+    let _: Foo = Foo.Bad(0);
+    //~^ ERROR expected value, found enum `Foo`
+    //~| HELP the following enum variants are available
+
+    let _: Bar = Bar(0);
+    //~^ ERROR expected function
+    //~| HELP try to construct one of the enum's variants
+    //~| HELP you might have meant to construct one of the enum's non-tuple variants
+
+    let _: Bar = Bar.C(0);
+    //~^ ERROR expected value, found enum `Bar`
+    //~| HELP use the path separator to refer to a variant
+
+    let _: Bar = Bar.E;
+    //~^ ERROR expected value, found enum `Bar`
+    //~| HELP use the path separator to refer to a variant
+
+    let _: Bar = Bar.Bad(0);
+    //~^ ERROR expected value, found enum `Bar`
+    //~| HELP you might have meant to use one of the following enum variants
+    //~| HELP alternatively, the following enum variants are also available
+
+    let _: Bar = Bar.Bad;
+    //~^ ERROR expected value, found enum `Bar`
+    //~| HELP you might have meant to use one of the following enum variants
+    //~| HELP alternatively, the following enum variants are also available
+
+    match Foo::A(42) {
+        A(..) => {}
+        //~^ ERROR cannot find tuple struct or tuple variant `A` in this scope
+        Foo(..) => {}
+        //~^ ERROR expected tuple struct or tuple variant
+        //~| HELP try to match against one of the enum's variants
+        _ => {}
+    }
+}
diff --git a/tests/ui/resolve/enum-expected-value-suggest-variants.stderr b/tests/ui/resolve/enum-expected-value-suggest-variants.stderr
new file mode 100644
index 00000000000..0bd6069b272
--- /dev/null
+++ b/tests/ui/resolve/enum-expected-value-suggest-variants.stderr
@@ -0,0 +1,225 @@
+error[E0423]: expected value, found enum `Foo`
+  --> $DIR/enum-expected-value-suggest-variants.rs:19:18
+   |
+LL |     let _: Foo = Foo.A(0);
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:1:1
+   |
+LL | / enum Foo {
+LL | |
+LL | |     A(u32),
+LL | |     B(u32),
+LL | | }
+   | |_^
+help: use the path separator to refer to a variant
+   |
+LL |     let _: Foo = Foo::A(0);
+   |                     ~~
+
+error[E0423]: expected value, found enum `Foo`
+  --> $DIR/enum-expected-value-suggest-variants.rs:23:18
+   |
+LL |     let _: Foo = Foo.Bad(0);
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:1:1
+   |
+LL | / enum Foo {
+LL | |
+LL | |     A(u32),
+LL | |     B(u32),
+LL | | }
+   | |_^
+help: the following enum variants are available
+   |
+LL |     let _: Foo = (Foo::A(/* fields */)).Bad(0);
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+LL |     let _: Foo = (Foo::B(/* fields */)).Bad(0);
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0423]: expected value, found enum `Bar`
+  --> $DIR/enum-expected-value-suggest-variants.rs:32:18
+   |
+LL |     let _: Bar = Bar.C(0);
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:7:1
+   |
+LL | / enum Bar {
+LL | |     C(u32),
+LL | |     D(u32),
+LL | |     E,
+LL | |     F,
+LL | | }
+   | |_^
+help: use the path separator to refer to a variant
+   |
+LL |     let _: Bar = Bar::C(0);
+   |                     ~~
+
+error[E0423]: expected value, found enum `Bar`
+  --> $DIR/enum-expected-value-suggest-variants.rs:36:18
+   |
+LL |     let _: Bar = Bar.E;
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:7:1
+   |
+LL | / enum Bar {
+LL | |     C(u32),
+LL | |     D(u32),
+LL | |     E,
+LL | |     F,
+LL | | }
+   | |_^
+help: use the path separator to refer to a variant
+   |
+LL |     let _: Bar = Bar::E;
+   |                     ~~
+
+error[E0423]: expected value, found enum `Bar`
+  --> $DIR/enum-expected-value-suggest-variants.rs:40:18
+   |
+LL |     let _: Bar = Bar.Bad(0);
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:7:1
+   |
+LL | / enum Bar {
+LL | |     C(u32),
+LL | |     D(u32),
+LL | |     E,
+LL | |     F,
+LL | | }
+   | |_^
+help: you might have meant to use one of the following enum variants
+   |
+LL |     let _: Bar = Bar::E.Bad(0);
+   |                  ~~~~~~
+LL |     let _: Bar = Bar::F.Bad(0);
+   |                  ~~~~~~
+help: alternatively, the following enum variants are also available
+   |
+LL |     let _: Bar = (Bar::C(/* fields */)).Bad(0);
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+LL |     let _: Bar = (Bar::D(/* fields */)).Bad(0);
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0423]: expected value, found enum `Bar`
+  --> $DIR/enum-expected-value-suggest-variants.rs:45:18
+   |
+LL |     let _: Bar = Bar.Bad;
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:7:1
+   |
+LL | / enum Bar {
+LL | |     C(u32),
+LL | |     D(u32),
+LL | |     E,
+LL | |     F,
+LL | | }
+   | |_^
+help: you might have meant to use one of the following enum variants
+   |
+LL |     let _: Bar = Bar::E.Bad;
+   |                  ~~~~~~
+LL |     let _: Bar = Bar::F.Bad;
+   |                  ~~~~~~
+help: alternatively, the following enum variants are also available
+   |
+LL |     let _: Bar = (Bar::C(/* fields */)).Bad;
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+LL |     let _: Bar = (Bar::D(/* fields */)).Bad;
+   |                  ~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0531]: cannot find tuple struct or tuple variant `A` in this scope
+  --> $DIR/enum-expected-value-suggest-variants.rs:51:9
+   |
+LL |         A(..) => {}
+   |         ^ not found in this scope
+   |
+help: consider importing this tuple variant
+   |
+LL + use Foo::A;
+   |
+
+error[E0532]: expected tuple struct or tuple variant, found enum `Foo`
+  --> $DIR/enum-expected-value-suggest-variants.rs:53:9
+   |
+LL |         Foo(..) => {}
+   |         ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:1:1
+   |
+LL | / enum Foo {
+LL | |
+LL | |     A(u32),
+LL | |     B(u32),
+LL | | }
+   | |_^
+help: try to match against one of the enum's variants
+   |
+LL |         Foo::A(..) => {}
+   |         ~~~~~~
+LL |         Foo::B(..) => {}
+   |         ~~~~~~
+
+error[E0423]: expected function, tuple struct or tuple variant, found enum `Foo`
+  --> $DIR/enum-expected-value-suggest-variants.rs:15:18
+   |
+LL |     let _: Foo = Foo(0);
+   |                  ^^^
+   |
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:1:1
+   |
+LL | / enum Foo {
+LL | |
+LL | |     A(u32),
+LL | |     B(u32),
+LL | | }
+   | |_^
+help: try to construct one of the enum's variants
+   |
+LL |     let _: Foo = Foo::A(0);
+   |                  ~~~~~~
+LL |     let _: Foo = Foo::B(0);
+   |                  ~~~~~~
+
+error[E0423]: expected function, tuple struct or tuple variant, found enum `Bar`
+  --> $DIR/enum-expected-value-suggest-variants.rs:27:18
+   |
+LL |     let _: Bar = Bar(0);
+   |                  ^^^
+   |
+   = help: you might have meant to construct one of the enum's non-tuple variants
+note: the enum is defined here
+  --> $DIR/enum-expected-value-suggest-variants.rs:7:1
+   |
+LL | / enum Bar {
+LL | |     C(u32),
+LL | |     D(u32),
+LL | |     E,
+LL | |     F,
+LL | | }
+   | |_^
+help: try to construct one of the enum's variants
+   |
+LL |     let _: Bar = Bar::C(0);
+   |                  ~~~~~~
+LL |     let _: Bar = Bar::D(0);
+   |                  ~~~~~~
+
+error: aborting due to 10 previous errors
+
+Some errors have detailed explanations: E0423, E0531, E0532.
+For more information about an error, try `rustc --explain E0423`.