Add Option and Result variants in prelude (FuelLabs#4504)

## Description

This also handles ambiguities in cases where a lone ident is either a
variable or a variant; or a variable declaration or an enum scrutinee.

Fix FuelLabs#4480

## Checklist

- [x] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [x] I have added tests that prove my fix is effective or that my
feature works.
- [x] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [x] I have requested a review from the relevant team or maintainers.

docs/book/src/advanced/generic_types.md

@@ -124,15 +124,15 @@ Similar to Rust, Sway has what is colloquially known as the [turbofish](https://
 
 ```sway
 fn foo<T, E>(t: T) -> Result<T, E> {
-    Result::Ok(t)
+    Ok(t)
 }
 ```
 
 In this code example, which is admittedly asinine, you can't possibly know what type `E` is. You'd need to provide the type manually, with a turbofish:
 
 ```sway
 fn foo<T, E>(t: T) -> Result<T, E> {
-    Result::Ok::<T, MyErrorType>(t)
+    Ok::<T, MyErrorType>(t)
 }
 ```
 

docs/book/src/blockchain-development/access_control.md

@@ -12,9 +12,9 @@ To deliver an experience akin to the EVM's access control, the `std` library pro
 
 The `msg_sender` function works as follows:
 
-- If the caller is a contract, then `Result::Ok(Sender)` is returned with the `ContractId` sender variant.
-- If the caller is external (i.e. from a script), then all coin input owners in the transaction are checked. If all owners are the same, then `Result::Ok(Sender)` is returned with the `Address` sender variant.
-- If the caller is external and coin input owners are different, then the caller cannot be determined and a `Result::Err(AuthError)` is returned.
+- If the caller is a contract, then `Ok(Sender)` is returned with the `ContractId` sender variant.
+- If the caller is external (i.e. from a script), then all coin input owners in the transaction are checked. If all owners are the same, then `Ok(Sender)` is returned with the `Address` sender variant.
+- If the caller is external and coin input owners are different, then the caller cannot be determined and a `Err(AuthError)` is returned.
 
 ## Contract Ownership
 

docs/book/src/common-collections/storage_map.md

@@ -45,7 +45,7 @@ We can get a value out of the storage map by providing its `key` to the `get` me
 {{#include ../../../../examples/storage_map/src/main.sw:storage_map_get}}
 ```
 
-Here, `value1` will have the value that's associated with the first address, and the result will be `42`. The `get` method returns an `Option<V>`; if there’s no value for that key in the storage map, `get` will return `Option::None`. This program handles the `Option` by calling `unwrap_or` to set `value1` to zero if `map` doesn't have an entry for the key.
+Here, `value1` will have the value that's associated with the first address, and the result will be `42`. The `get` method returns an `Option<V>`; if there’s no value for that key in the storage map, `get` will return `None`. This program handles the `Option` by calling `unwrap_or` to set `value1` to zero if `map` doesn't have an entry for the key.
 
 ## Storage Maps with Multiple Keys
 

docs/reference/src/code/examples/access-control/ownership/src/main.sw

@@ -2,7 +2,7 @@ contract;
 
 // ANCHOR: identity
 storage {
-    owner: Option<Identity> = Option::None,
+    owner: Option<Identity> = None,
 }
 
 // ANCHOR_END: identity

docs/reference/src/documentation/misc/prelude.md

@@ -9,8 +9,12 @@ The prelude contains the following:
 - [`Identity`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/identity.sw): An enum containing `Address` & `ContractID` structs
 - [`Vec`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/vec.sw): A growable, heap-allocated vector
 - [`StorageMap`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/storage.sw): A key-value mapping in contract storage
-- [`Option`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/option.sw): An enum containing either some generic value `<T>` or an absence of that value
-- [`Result`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/result.sw): An enum used to represent either a success or failure of an operation
+- [`Option`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/option.sw): An enum containing either some generic value `<T>` or an absence of that value, we also expose the variants directly:
+  - `Some`
+  - `None`
+- [`Result`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/result.sw): An enum used to represent either a success or failure of an operation, we also expose the variants directly:
+  - `Ok`
+  - `Err`
 - [`assert`](https://github.com/FuelLabs/sway/blob/master/sway-lib-std/src/assert.sw): A module containing
   - `assert`: A function that reverts the VM if the condition provided to it is false
   - `assert_eq`: A function that reverts the VM and logs its two inputs v1 and v2 if the condition v1 == v2 is false

docs/reference/src/documentation/operations/storage/libraries/storage-map.md

@@ -20,7 +20,7 @@ There are two `storage` variables: `balance` & `user`. `balance` takes a single
 
 ## Reading from Storage
 
-Retrieving data from a storage variable is done through the `.get(key)` method. That is to say that we state which storage variable we would like to read from and append `.get()` to the end while providing the key for the data that we want to retrieve. The method `get` returns an `Option`; if there is no value for `key` in the map, `get` will return `Option::None`.
+Retrieving data from a storage variable is done through the `.get(key)` method. That is to say that we state which storage variable we would like to read from and append `.get()` to the end while providing the key for the data that we want to retrieve. The method `get` returns an `Option`; if there is no value for `key` in the map, `get` will return `None`.
 
 In this example we wrap the [`Identity`](../../namespace/identity.md) of the caller with their provided `id` into a [tuple](../../../language/built-ins/tuples.md) and use that as the key.
 

docs/reference/src/documentation/operations/storage/libraries/store-get.md

@@ -30,4 +30,4 @@ In this example we retrieve some `u64` at the position of `key`.
 {{#include ../../../../code/operations/storage/store_get/src/main.sw:get}}
 ```
 
-The function `get` returns an `Option`; if the storage slots requested have not been set before, `get` will return `Option::None`.
+The function `get` returns an `Option`; if the storage slots requested have not been set before, `get` will return `None`.

examples/option/src/main.sw

@@ -2,9 +2,9 @@ script;
 
 fn divide(numerator: u64, denominator: u64) -> Option<u64> {
     if denominator == 0 {
-        Option::None
+        None
     } else {
-        Option::Some(numerator / denominator)
+        Some(numerator / denominator)
     }
 }
 
@@ -13,8 +13,8 @@ fn main() {
     // Pattern match to retrieve the value
     match result {
         // The division was valid
-        Option::Some(x) => std::logging::log(x),
+        Some(x) => std::logging::log(x),
         // The division was invalid
-        Option::None => std::logging::log("Cannot divide by 0"),
+        None => std::logging::log("Cannot divide by 0"),
     }
 }

examples/ownership/src/main.sw

@@ -10,20 +10,20 @@ abi OwnershipExample {
 }
 
 storage {
-    owner: Option<Identity> = Option::None,
+    owner: Option<Identity> = None,
 }
 
 impl OwnershipExample for Contract {
     // ANCHOR: revoke_owner_example
     #[storage(write)]
     fn revoke_ownership() {
-        storage.owner.write(Option::None);
+        storage.owner.write(None);
     }
     // ANCHOR_END: revoke_owner_example
     // ANCHOR: set_owner_example
     #[storage(write)]
     fn set_owner(identity: Identity) {
-        storage.owner.write(Option::Some(identity));
+        storage.owner.write(Some(identity));
     }
     // ANCHOR_END: set_owner_example
     #[storage(read)]

examples/result/src/main.sw

@@ -6,16 +6,16 @@ enum MyContractError {
 
 fn divide(numerator: u64, denominator: u64) -> Result<u64, MyContractError> {
     if (denominator == 0) {
-        return Result::Err(MyContractError::DivisionByZero);
+        return Err(MyContractError::DivisionByZero);
     } else {
-        Result::Ok(numerator / denominator)
+        Ok(numerator / denominator)
     }
 }
 
 fn main() -> Result<u64, str[4]> {
     let result = divide(20, 2);
     match result {
-        Result::Ok(value) => Result::Ok(value),
-        Result::Err(MyContractError::DivisionByZero) => Result::Err("Fail"),
+        Ok(value) => Ok(value),
+        Err(MyContractError::DivisionByZero) => Err("Fail"),
     }
 }

examples/signatures/src/main.sw

@@ -14,7 +14,7 @@ fn main() {
 
     // A recovered Fuel address.
     let result_address: Result<Address, EcRecoverError> = ec_recover_address(signature, MSG_HASH);
-    if let Result::Ok(address) = result_address {
+    if let Ok(address) = result_address {
         log(address.value);
     } else {
         revert(0);

examples/storage_vec/src/main.sw

@@ -54,8 +54,8 @@ impl StorageVecContract for Contract {
     fn read_from_storage_vec() {
         let third = storage.v.get(2);
         match third {
-            Option::Some(third) => log(third.read()),
-            Option::None => revert(42),
+            Some(third) => log(third.read()),
+            None => revert(42),
         }
     }
     // ANCHOR_END: storage_vec_get

examples/vec/src/main.sw

@@ -15,8 +15,8 @@ fn main() {
     // ANCHOR: vec_get
     let third = v.get(2);
     match third {
-        Option::Some(third) => log(third),
-        Option::None => revert(42),
+        Some(third) => log(third),
+        None => revert(42),
     }
     // ANCHOR_END: vec_get
     // ANCHOR: vec_get_oob

sway-ast/src/pattern.rs

@@ -10,6 +10,8 @@ pub enum Pattern {
     Wildcard {
         underscore_token: UnderscoreToken,
     },
+    /// A pattern made of a single ident, which could either be a variable or an enum variant
+    AmbiguousSingleIdent(Ident),
     Var {
         reference: Option<RefToken>,
         mutable: Option<MutToken>,
@@ -51,6 +53,7 @@ impl Spanned for Pattern {
                 (None, Some(mut_token)) => Span::join(mut_token.span(), name.span()),
                 (None, None) => name.span(),
             },
+            Pattern::AmbiguousSingleIdent(ident) => ident.span(),
             Pattern::Literal(literal) => literal.span(),
             Pattern::Constant(path_expr) => path_expr.span(),
             Pattern::Constructor { path, args } => Span::join(path.span(), args.span()),

sway-core/src/language/parsed/expression/mod.rs

@@ -164,10 +164,12 @@ pub enum ExpressionKind {
     Error(Box<[Span]>),
     Literal(Literal),
     /// An ambiguous path where we don't know until type checking whether this
-    /// is a free function call or a UFCS (Rust term) style associated function call.
+    /// is a free function call, an enum variant or a UFCS (Rust term) style associated function call.
     AmbiguousPathExpression(Box<AmbiguousPathExpression>),
     FunctionApplication(Box<FunctionApplicationExpression>),
     LazyOperator(LazyOperatorExpression),
+    /// And ambiguous single ident which could either be a variable or an enum variant
+    AmbiguousVariableExpression(Ident),
     Variable(Ident),
     Tuple(Vec<Expression>),
     TupleIndex(TupleIndexExpression),

sway-core/src/language/parsed/expression/scrutinee.rs

@@ -26,6 +26,7 @@ pub enum Scrutinee {
         name: Ident,
         span: Span,
     },
+    AmbiguousSingleIdent(Ident),
     StructScrutinee {
         struct_name: CallPath,
         fields: Vec<StructScrutineeField>,
@@ -66,6 +67,7 @@ impl Spanned for Scrutinee {
             Scrutinee::CatchAll { span } => span.clone(),
             Scrutinee::Literal { span, .. } => span.clone(),
             Scrutinee::Variable { span, .. } => span.clone(),
+            Scrutinee::AmbiguousSingleIdent(ident) => ident.span(),
             Scrutinee::StructScrutinee { span, .. } => span.clone(),
             Scrutinee::EnumScrutinee { span, .. } => span.clone(),
             Scrutinee::Tuple { span, .. } => span.clone(),
@@ -168,6 +170,7 @@ impl Scrutinee {
                 .collect::<Vec<TypeInfo>>(),
             Scrutinee::Literal { .. }
             | Scrutinee::CatchAll { .. }
+            | Scrutinee::AmbiguousSingleIdent(..)
             | Scrutinee::Variable { .. }
             | Scrutinee::Error { .. } => {
                 vec![]

sway-core/src/semantic_analysis/ast_node/expression/match_expression/typed/typed_scrutinee.rs

@@ -79,6 +79,27 @@ impl ty::TyScrutinee {
                 value,
                 span,
             } => type_check_enum(ctx, call_path, *value, span),
+            Scrutinee::AmbiguousSingleIdent(ident) => {
+                let maybe_enum = type_check_enum(
+                    ctx.by_ref(),
+                    CallPath {
+                        prefixes: vec![],
+                        suffix: ident.clone(),
+                        is_absolute: false,
+                    },
+                    Scrutinee::Tuple {
+                        elems: vec![],
+                        span: ident.span(),
+                    },
+                    ident.span(),
+                );
+
+                if maybe_enum.is_ok() {
+                    maybe_enum
+                } else {
+                    type_check_variable(ctx, ident.clone(), ident.span())
+                }
+            }
             Scrutinee::Tuple { elems, span } => type_check_tuple(ctx, elems, span),
             Scrutinee::Error { .. } => err(vec![], vec![]),
         }

sway-core/src/semantic_analysis/ast_node/expression/typed_expression.rs

@@ -122,6 +122,30 @@ impl ty::TyExpression {
             // We've already emitted an error for the `::Error` case.
             ExpressionKind::Error(_) => ok(ty::TyExpression::error(span, engines), vec![], vec![]),
             ExpressionKind::Literal(lit) => Self::type_check_literal(engines, lit, span),
+            ExpressionKind::AmbiguousVariableExpression(name) => {
+                let call_path = CallPath {
+                    prefixes: vec![],
+                    suffix: name.clone(),
+                    is_absolute: false,
+                };
+                if matches!(
+                    ctx.namespace.resolve_call_path(&call_path).value,
+                    Some(ty::TyDecl::EnumVariantDecl { .. })
+                ) {
+                    Self::type_check_delineated_path(
+                        ctx.by_ref(),
+                        TypeBinding {
+                            span: call_path.span(),
+                            inner: call_path,
+                            type_arguments: TypeArgs::Regular(vec![]),
+                        },
+                        span,
+                        None,
+                    )
+                } else {
+                    Self::type_check_variable_expression(ctx.by_ref(), name, span)
+                }
+            }
             ExpressionKind::Variable(name) => {
                 Self::type_check_variable_expression(ctx.by_ref(), name, span)
             }

sway-core/src/semantic_analysis/node_dependencies.rs

@@ -454,6 +454,9 @@ impl Dependencies {
                 // ordered
                 self.gather_from_call_path(&(name.clone()).into(), false, false)
             }
+            ExpressionKind::AmbiguousVariableExpression(name) => {
+                self.gather_from_call_path(&(name.clone()).into(), false, false)
+            }
             ExpressionKind::FunctionApplication(function_application_expression) => {
                 let FunctionApplicationExpression {
                     call_path_binding,

sway-core/src/transform/to_parsed_lang/convert_parse_tree.rs

@@ -2366,6 +2366,7 @@ fn fn_arg_to_function_parameter(
             mutable,
             name,
         } => (reference, mutable, name),
+        Pattern::AmbiguousSingleIdent(ident) => (None, None, ident),
         Pattern::Literal(..) => {
             let error = ConvertParseTreeError::LiteralPatternsNotSupportedHere { span: pat_span };
             return Err(handler.emit_err(error.into()));
@@ -2541,10 +2542,15 @@ fn path_expr_to_expression(
     path_expr: PathExpr,
 ) -> Result<Expression, ErrorEmitted> {
     let span = path_expr.span();
-    let expression = if path_expr.root_opt.is_none() && path_expr.suffix.is_empty() {
+    let expression = if path_expr.root_opt.is_none()
+        && path_expr.suffix.is_empty()
+        && path_expr.prefix.generics_opt.is_none()
+    {
+        // only `foo`, it coult either be a variable or an enum variant
+
         let name = path_expr_segment_to_ident(context, handler, &path_expr.prefix)?;
         Expression {
-            kind: ExpressionKind::Variable(name),
+            kind: ExpressionKind::AmbiguousVariableExpression(name),
             span,
         }
     } else {
@@ -3076,14 +3082,15 @@ fn statement_let_to_ast_nodes(
         span: Span,
     ) -> Result<Vec<AstNode>, ErrorEmitted> {
         let ast_nodes = match pattern {
-            Pattern::Wildcard { .. } | Pattern::Var { .. } => {
+            Pattern::Wildcard { .. } | Pattern::Var { .. } | Pattern::AmbiguousSingleIdent(..) => {
                 let (reference, mutable, name) = match pattern {
                     Pattern::Var {
                         reference,
                         mutable,
                         name,
                     } => (reference, mutable, name),
                     Pattern::Wildcard { .. } => (None, None, Ident::new_no_span("_".into())),
+                    Pattern::AmbiguousSingleIdent(ident) => (None, None, ident),
                     _ => unreachable!(),
                 };
                 if reference.is_some() {
@@ -3474,6 +3481,7 @@ fn pattern_to_scrutinee(
             }
             Scrutinee::Variable { name, span }
         }
+        Pattern::AmbiguousSingleIdent(ident) => Scrutinee::AmbiguousSingleIdent(ident),
         Pattern::Literal(literal) => Scrutinee::Literal {
             value: literal_to_literal(context, handler, literal)?,
             span,