feat: add Expr::resolve and TypedExpr::as_function_definition (#5859)

# Description

## Problem

Part of #5668

## Summary



## Additional Context



## Documentation

Check one:
- [ ] No documentation needed.
- [x] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

---------

Co-authored-by: jfecher <[email protected]>

Author: asterite

compiler/noirc_frontend/src/elaborator/statements.rs

@@ -48,7 +48,7 @@ impl<'context> Elaborator<'context> {
         }
     }
 
-    pub(super) fn elaborate_statement(&mut self, statement: Statement) -> (StmtId, Type) {
+    pub(crate) fn elaborate_statement(&mut self, statement: Statement) -> (StmtId, Type) {
         let span = statement.span;
         let (hir_statement, typ) = self.elaborate_statement_value(statement);
         let id = self.interner.push_stmt(hir_statement);

compiler/noirc_frontend/src/hir/comptime/interpreter/builtin.rs

@@ -8,9 +8,9 @@ use builtin_helpers::{
     block_expression_to_value, check_argument_count, check_function_not_yet_resolved,
     check_one_argument, check_three_arguments, check_two_arguments, get_expr, get_field,
     get_function_def, get_module, get_quoted, get_slice, get_struct, get_trait_constraint,
-    get_trait_def, get_trait_impl, get_tuple, get_type, get_u32, get_unresolved_type,
-    hir_pattern_to_tokens, mutate_func_meta_type, parse, replace_func_meta_parameters,
-    replace_func_meta_return_type,
+    get_trait_def, get_trait_impl, get_tuple, get_type, get_typed_expr, get_u32,
+    get_unresolved_type, hir_pattern_to_tokens, mutate_func_meta_type, parse,
+    replace_func_meta_parameters, replace_func_meta_return_type,
 };
 use chumsky::{prelude::choice, Parser};
 use im::Vector;
@@ -25,7 +25,11 @@ use crate::{
         FunctionReturnType, IntegerBitSize, LValue, Literal, Statement, StatementKind, UnaryOp,
         UnresolvedType, UnresolvedTypeData, Visibility,
     },
-    hir::comptime::{errors::IResult, value::ExprValue, InterpreterError, Value},
+    hir::comptime::{
+        errors::IResult,
+        value::{ExprValue, TypedExpr},
+        InterpreterError, Value,
+    },
     hir_def::function::FunctionBody,
     macros_api::{HirExpression, HirLiteral, ModuleDefId, NodeInterner, Signedness},
     node_interner::{DefinitionKind, TraitImplKind},
@@ -87,6 +91,7 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "expr_has_semicolon" => expr_has_semicolon(interner, arguments, location),
             "expr_is_break" => expr_is_break(interner, arguments, location),
             "expr_is_continue" => expr_is_continue(interner, arguments, location),
+            "expr_resolve" => expr_resolve(self, arguments, location),
             "is_unconstrained" => Ok(Value::Bool(true)),
             "function_def_body" => function_def_body(interner, arguments, location),
             "function_def_name" => function_def_name(interner, arguments, location),
@@ -145,6 +150,9 @@ impl<'local, 'context> Interpreter<'local, 'context> {
             "type_is_bool" => type_is_bool(arguments, location),
             "type_is_field" => type_is_field(arguments, location),
             "type_of" => type_of(arguments, location),
+            "typed_expr_as_function_definition" => {
+                typed_expr_as_function_definition(interner, arguments, return_type, location)
+            }
             "unresolved_type_is_field" => unresolved_type_is_field(interner, arguments, location),
             "zeroed" => zeroed(return_type),
             _ => {
@@ -763,6 +771,23 @@ fn trait_impl_trait_generic_args(
     Ok(Value::Slice(trait_generics, slice_type))
 }
 
+fn typed_expr_as_function_definition(
+    interner: &NodeInterner,
+    arguments: Vec<(Value, Location)>,
+    return_type: Type,
+    location: Location,
+) -> IResult<Value> {
+    let self_argument = check_one_argument(arguments, location)?;
+    let typed_expr = get_typed_expr(self_argument)?;
+    let option_value = if let TypedExpr::ExprId(expr_id) = typed_expr {
+        let func_id = interner.lookup_function_from_expr(&expr_id);
+        func_id.map(Value::FunctionDefinition)
+    } else {
+        None
+    };
+    option(return_type, option_value)
+}
+
 // fn is_field(self) -> bool
 fn unresolved_type_is_field(
     interner: &NodeInterner,
@@ -1380,7 +1405,48 @@ where
     F: FnOnce(ExprValue) -> Option<Value>,
 {
     let self_argument = check_one_argument(arguments, location)?;
-    let mut expr_value = get_expr(interner, self_argument)?;
+    let expr_value = get_expr(interner, self_argument)?;
+    let expr_value = unwrap_expr_value(interner, expr_value);
+
+    let option_value = f(expr_value);
+    option(return_type, option_value)
+}
+
+// fn resolve(self) -> TypedExpr
+fn expr_resolve(
+    interpreter: &mut Interpreter,
+    arguments: Vec<(Value, Location)>,
+    location: Location,
+) -> IResult<Value> {
+    let self_argument = check_one_argument(arguments, location)?;
+    let self_argument_location = self_argument.1;
+    let expr_value = get_expr(interpreter.elaborator.interner, self_argument)?;
+    let expr_value = unwrap_expr_value(interpreter.elaborator.interner, expr_value);
+
+    let value =
+        interpreter.elaborate_item(interpreter.current_function, |elaborator| match expr_value {
+            ExprValue::Expression(expression_kind) => {
+                let expr = Expression { kind: expression_kind, span: self_argument_location.span };
+                let (expr_id, _) = elaborator.elaborate_expression(expr);
+                Value::TypedExpr(TypedExpr::ExprId(expr_id))
+            }
+            ExprValue::Statement(statement_kind) => {
+                let statement =
+                    Statement { kind: statement_kind, span: self_argument_location.span };
+                let (stmt_id, _) = elaborator.elaborate_statement(statement);
+                Value::TypedExpr(TypedExpr::StmtId(stmt_id))
+            }
+            ExprValue::LValue(lvalue) => {
+                let expr = lvalue.as_expression();
+                let (expr_id, _) = elaborator.elaborate_expression(expr);
+                Value::TypedExpr(TypedExpr::ExprId(expr_id))
+            }
+        });
+
+    Ok(value)
+}
+
+fn unwrap_expr_value(interner: &NodeInterner, mut expr_value: ExprValue) -> ExprValue {
     loop {
         match expr_value {
             ExprValue::Expression(ExpressionKind::Parenthesized(expression)) => {
@@ -1402,9 +1468,7 @@ where
             _ => break,
         }
     }
-
-    let option_value = f(expr_value);
-    option(return_type, option_value)
+    expr_value
 }
 
 // fn body(self) -> Expr

compiler/noirc_frontend/src/hir/comptime/interpreter/builtin/builtin_helpers.rs

@@ -11,7 +11,7 @@ use crate::{
     hir::{
         comptime::{
             errors::IResult,
-            value::{add_token_spans, ExprValue},
+            value::{add_token_spans, ExprValue, TypedExpr},
             Interpreter, InterpreterError, Value,
         },
         def_map::ModuleId,
@@ -227,6 +227,13 @@ pub(crate) fn get_type((value, location): (Value, Location)) -> IResult<Type> {
     }
 }
 
+pub(crate) fn get_typed_expr((value, location): (Value, Location)) -> IResult<TypedExpr> {
+    match value {
+        Value::TypedExpr(typed_expr) => Ok(typed_expr),
+        value => type_mismatch(value, Type::Quoted(QuotedType::TypedExpr), location),
+    }
+}
+
 pub(crate) fn get_quoted((value, location): (Value, Location)) -> IResult<Rc<Vec<Token>>> {
     match value {
         Value::Quoted(tokens) => Ok(tokens),

compiler/noirc_frontend/src/hir/comptime/value.rs

@@ -24,7 +24,7 @@ use crate::{
         Expression, ExpressionKind, HirExpression, HirLiteral, Literal, NodeInterner, Path,
         StructId,
     },
-    node_interner::{ExprId, FuncId, TraitId, TraitImplId},
+    node_interner::{ExprId, FuncId, StmtId, TraitId, TraitImplId},
     parser::{self, NoirParser, TopLevelStatement},
     token::{SpannedToken, Token, Tokens},
     QuotedType, Shared, Type, TypeBindings,
@@ -69,6 +69,7 @@ pub enum Value {
     Type(Type),
     Zeroed(Type),
     Expr(ExprValue),
+    TypedExpr(TypedExpr),
     UnresolvedType(UnresolvedTypeData),
 }
 
@@ -79,6 +80,12 @@ pub enum ExprValue {
     LValue(LValue),
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Display)]
+pub enum TypedExpr {
+    ExprId(ExprId),
+    StmtId(StmtId),
+}
+
 impl Value {
     pub(crate) fn expression(expr: ExpressionKind) -> Self {
         Value::Expr(ExprValue::Expression(expr))
@@ -137,6 +144,7 @@ impl Value {
             Value::Type(_) => Type::Quoted(QuotedType::Type),
             Value::Zeroed(typ) => return Cow::Borrowed(typ),
             Value::Expr(_) => Type::Quoted(QuotedType::Expr),
+            Value::TypedExpr(_) => Type::Quoted(QuotedType::TypedExpr),
             Value::UnresolvedType(_) => Type::Quoted(QuotedType::UnresolvedType),
         })
     }
@@ -264,7 +272,8 @@ impl Value {
                     statements: vec![Statement { kind: statement, span: location.span }],
                 })
             }
-            Value::Expr(ExprValue::LValue(_))
+            Value::Expr(ExprValue::LValue(lvalue)) => lvalue.as_expression().kind,
+            Value::TypedExpr(..)
             | Value::Pointer(..)
             | Value::StructDefinition(_)
             | Value::TraitConstraint(..)
@@ -389,7 +398,9 @@ impl Value {
                 HirExpression::Literal(HirLiteral::Slice(HirArrayLiteral::Standard(elements)))
             }
             Value::Quoted(tokens) => HirExpression::Unquote(add_token_spans(tokens, location.span)),
-            Value::Expr(..)
+            Value::TypedExpr(TypedExpr::ExprId(expr_id)) => interner.expression(&expr_id),
+            Value::TypedExpr(TypedExpr::StmtId(..))
+            | Value::Expr(..)
             | Value::Pointer(..)
             | Value::StructDefinition(_)
             | Value::TraitConstraint(..)
@@ -621,6 +632,7 @@ impl<'value, 'interner> Display for ValuePrinter<'value, 'interner> {
             Value::Expr(ExprValue::LValue(lvalue)) => {
                 write!(f, "{}", remove_interned_in_lvalue(self.interner, lvalue.clone()))
             }
+            Value::TypedExpr(_) => write!(f, "(typed expr)"),
             Value::UnresolvedType(typ) => {
                 if let UnresolvedTypeData::Interned(id) = typ {
                     let typ = self.interner.get_unresolved_type_data(*id);

compiler/noirc_frontend/src/hir_def/types.rs

@@ -153,6 +153,7 @@ pub enum QuotedType {
     Quoted,
     TopLevelItem,
     Type,
+    TypedExpr,
     StructDefinition,
     TraitConstraint,
     TraitDefinition,
@@ -741,6 +742,7 @@ impl std::fmt::Display for QuotedType {
             QuotedType::Quoted => write!(f, "Quoted"),
             QuotedType::TopLevelItem => write!(f, "TopLevelItem"),
             QuotedType::Type => write!(f, "Type"),
+            QuotedType::TypedExpr => write!(f, "TypedExpr"),
             QuotedType::StructDefinition => write!(f, "StructDefinition"),
             QuotedType::TraitDefinition => write!(f, "TraitDefinition"),
             QuotedType::TraitConstraint => write!(f, "TraitConstraint"),

compiler/noirc_frontend/src/lexer/token.rs

@@ -962,6 +962,7 @@ pub enum Keyword {
     TraitDefinition,
     TraitImpl,
     Type,
+    TypedExpr,
     TypeType,
     Unchecked,
     Unconstrained,
@@ -1017,6 +1018,7 @@ impl fmt::Display for Keyword {
             Keyword::TraitDefinition => write!(f, "TraitDefinition"),
             Keyword::TraitImpl => write!(f, "TraitImpl"),
             Keyword::Type => write!(f, "type"),
+            Keyword::TypedExpr => write!(f, "TypedExpr"),
             Keyword::TypeType => write!(f, "Type"),
             Keyword::Unchecked => write!(f, "unchecked"),
             Keyword::Unconstrained => write!(f, "unconstrained"),
@@ -1075,6 +1077,7 @@ impl Keyword {
             "TraitImpl" => Keyword::TraitImpl,
             "type" => Keyword::Type,
             "Type" => Keyword::TypeType,
+            "TypedExpr" => Keyword::TypedExpr,
             "StructDefinition" => Keyword::StructDefinition,
             "unchecked" => Keyword::Unchecked,
             "unconstrained" => Keyword::Unconstrained,

compiler/noirc_frontend/src/parser/parser/types.rs

@@ -88,6 +88,7 @@ pub(super) fn comptime_type() -> impl NoirParser<UnresolvedType> {
         type_of_quoted_types(),
         top_level_item_type(),
         quoted_type(),
+        typed_expr_type(),
     ))
 }
 
@@ -159,6 +160,12 @@ fn quoted_type() -> impl NoirParser<UnresolvedType> {
         .map_with_span(|_, span| UnresolvedTypeData::Quoted(QuotedType::Quoted).with_span(span))
 }
 
+/// This is the type of a typed/resolved expression.
+fn typed_expr_type() -> impl NoirParser<UnresolvedType> {
+    keyword(Keyword::TypedExpr)
+        .map_with_span(|_, span| UnresolvedTypeData::Quoted(QuotedType::TypedExpr).with_span(span))
+}
+
 /// This is the type of an already resolved type.
 /// The only way this can appear in the token input is if an already resolved `Type` object
 /// was spliced into a macro's token stream via the `$` operator.

docs/docs/noir/concepts/comptime.md

@@ -232,6 +232,7 @@ The following is an incomplete list of some `comptime` types along with some use
     - `fn fields(self) -> [(Quoted, Type)]`
       - Return the name and type of each field
 - `TraitConstraint`: A trait constraint such as `From<Field>`
+- `TypedExpr`: A type-checked expression.
 - `UnresolvedType`: A syntactic notation that refers to a Noir type that hasn't been resolved yet
 
 There are many more functions available by exploring the `std::meta` module and its submodules.

docs/docs/noir/standard_library/meta/expr.md

@@ -184,4 +184,10 @@ for expressions that are integers, doubling them, would return `(&[2], &[4, 6])`
 
 #include_code quoted noir_stdlib/src/meta/expr.nr rust
 
-Returns this expression as a `Quoted` value. It's the same as `quote { $self }`.
+Returns this expression as a `Quoted` value. It's the same as `quote { $self }`.
+
+### resolve
+
+#include_code resolve noir_stdlib/src/meta/expr.nr rust
+
+Resolves and type-checks this expression and returns the result as a `TypedExpr`. If any names used by this expression are not in scope or if there are any type errors, this will give compiler errors as if the expression was written directly into the current `comptime` function.

docs/docs/noir/standard_library/meta/typed_expr.md

@@ -0,0 +1,13 @@
+---
+title: TypedExpr
+---
+
+`std::meta::typed_expr` contains methods on the built-in `TypedExpr` type for resolved and type-checked expressions.
+
+## Methods
+
+### as_function_definition
+
+#include_code as_function_definition noir_stdlib/src/meta/typed_expr.nr rust
+
+If this expression refers to a function definitions, returns it. Otherwise returns `Option::none()`.