Improve error message for illegal enum variants

sway-error/src/parser_error.rs

@@ -94,6 +94,8 @@ pub enum ParseErrorKind {
     UnexpectedTokenAfterSliceType,
     #[error("Expected a path type.")]
     ExpectedPathType,
+    #[error("Expected ':'. Enum variants must be in the form `Variant: ()`, `Variant: <type>`, or `Variant: (<type1>, ..., <typeN>)`. E.g., `Foo: (), or `Bar: (bool, u32)`.")]
+    MissingColonInEnumTypeField,
 }
 
 #[derive(Debug, Error, Clone, PartialEq, Eq, Hash)]

sway-parse/src/item/mod.rs

@@ -1,8 +1,8 @@
 use crate::{Parse, ParseResult, ParseToEnd, Parser, ParserConsumed};
 
 use sway_ast::keywords::{
-    AbiToken, ClassToken, ConfigurableToken, ConstToken, EnumToken, FnToken, ImplToken, ModToken,
-    MutToken, OpenAngleBracketToken, RefToken, SelfToken, SemicolonToken, StorageToken,
+    AbiToken, ClassToken, ColonToken, ConfigurableToken, ConstToken, EnumToken, FnToken, ImplToken,
+    ModToken, MutToken, OpenAngleBracketToken, RefToken, SelfToken, SemicolonToken, StorageToken,
     StructToken, TraitToken, TypeToken, UseToken, WhereToken,
 };
 use sway_ast::{
@@ -96,7 +96,11 @@ impl Parse for TypeField {
     fn parse(parser: &mut Parser) -> ParseResult<TypeField> {
         Ok(TypeField {
             name: parser.parse()?,
-            colon_token: parser.parse()?,
+            colon_token: if parser.peek::<ColonToken>().is_some() {
+                parser.parse()
+            } else {
+                Err(parser.emit_error(ParseErrorKind::MissingColonInEnumTypeField))
+            }?,
             ty: parser.parse()?,
         })
     }

test/src/e2e_vm_tests/test_programs/should_fail/enum_rust_like/Forc.lock

@@ -0,0 +1,8 @@
+[[package]]
+name = "core"
+source = "path+from-root-EC2C1FC903667D61"
+
+[[package]]
+name = "enum_rust_like"
+source = "member"
+dependencies = ["core"]

test/src/e2e_vm_tests/test_programs/should_fail/enum_rust_like/Forc.toml

@@ -0,0 +1,8 @@
+[project]
+authors = ["Fuel Labs <[email protected]>"]
+entry = "main.sw"
+license = "Apache-2.0"
+name = "enum_rust_like"
+
+[dependencies]
+core = { path = "../../../../../../sway-lib-core" }

test/src/e2e_vm_tests/test_programs/should_fail/enum_rust_like/json_abi_oracle.json

@@ -0,0 +1 @@
+[]

test/src/e2e_vm_tests/test_programs/should_fail/enum_rust_like/src/main.sw

@@ -0,0 +1,18 @@
+script;
+
+// A developer familiar with Rust might be tempted to define enum variants as `Foo` or `Bar(u32)`.
+// This file tests the error message that informs the developer of the correct syntax.
+
+enum Enum1 {
+  Ok,    // Illegal
+  Err,   // Also illegal, but shadowed by previous error
+}
+
+enum Enum2 {
+  F(u32),        // Illegal
+  G(u32, u32),   // Also illegal, but shadowed by previous error
+}
+
+fn main() {
+}
+

test/src/e2e_vm_tests/test_programs/should_fail/enum_rust_like/test.toml

@@ -0,0 +1,11 @@
+category = "fail"
+
+# check: $()error
+# check: enum_rust_like/src/main.sw:7:5
+# check: $()Ok,    // Illegal
+# nextln: $()Expected ':'. Enum variants must be in the form `Variant: ()`, `Variant: <type>`, or `Variant: (<type1>, ..., <typeN>)`. E.g., `Foo: (), or `Bar: (bool, u32)`.
+
+# check: $()error
+# check: enum_rust_like/src/main.sw:12:4
+# check: $()F(u32),        // Illegal
+# nextln: $()Expected ':'. Enum variants must be in the form `Variant: ()`, `Variant: <type>`, or `Variant: (<type1>, ..., <typeN>)`. E.g., `Foo: (), or `Bar: (bool, u32)`.