Revert "cl-ast: Unify break, return, and unary expressions"

This reverts commit adb0fd229c.

compiler/cl-ast/src/ast.rs

@@ -398,6 +398,10 @@ pub enum ExprKind {
     If(If),
     /// A [For] expression: `for` Pattern `in` [`Expr`] [`Block`] [`Else`]?
     For(For),
+    /// A [Break] expression: `break` [`Expr`]?
+    Break(Break),
+    /// A [Return] expression `return` [`Expr`]?
+    Return(Return),
     /// A continue expression: `continue`
     Continue,
 }
@@ -478,8 +482,6 @@ pub enum UnaryKind {
     Not,
     /// A Loop expression: `loop` [`Block`]
     Loop,
-    Break,
-    Return,
     /// Unused
     At,
     /// Unused
@@ -598,3 +600,15 @@ pub struct For {
 pub struct Else {
     pub body: Option<Box<Expr>>,
 }
+
+/// A [Break] expression: `break` [`Expr`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Break {
+    pub body: Option<Box<Expr>>,
+}
+
+/// A [Return] expression `return` [`Expr`]?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Return {
+    pub body: Option<Box<Expr>>,
+}

compiler/cl-ast/src/ast_impl.rs

@@ -451,6 +451,8 @@ mod display {
                 ExprKind::While(v) => v.fmt(f),
                 ExprKind::If(v) => v.fmt(f),
                 ExprKind::For(v) => v.fmt(f),
+                ExprKind::Break(v) => v.fmt(f),
+                ExprKind::Return(v) => v.fmt(f),
                 ExprKind::Continue => "continue".fmt(f),
             }
         }
@@ -540,8 +542,6 @@ mod display {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             match self {
                 UnaryKind::Loop => "loop ",
-                UnaryKind::Break => "break ",
-                UnaryKind::Return => "return ",
                 UnaryKind::Deref => "*",
                 UnaryKind::Neg => "-",
                 UnaryKind::Not => "!",
@@ -684,6 +684,26 @@ mod display {
             }
         }
     }
+
+    impl Display for Break {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "break")?;
+            match &self.body {
+                Some(body) => write!(f, " {body}"),
+                _ => Ok(()),
+            }
+        }
+    }
+
+    impl Display for Return {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "return")?;
+            match &self.body {
+                Some(body) => write!(f, " {body}"),
+                _ => Ok(()),
+            }
+        }
+    }
 }
 
 mod convert {
@@ -767,6 +787,8 @@ mod convert {
             While => ExprKind::While,
             If => ExprKind::If,
             For => ExprKind::For,
+            Break => ExprKind::Break,
+            Return => ExprKind::Return,
         }
         impl From for Literal {
             bool => Literal::Bool,

compiler/cl-ast/src/ast_visitor/fold.rs

@@ -368,6 +368,14 @@ pub trait Fold {
         let Else { body } = e;
         Else { body: body.map(|e| Box::new(self.fold_expr(*e))) }
     }
+    fn fold_break(&mut self, b: Break) -> Break {
+        let Break { body } = b;
+        Break { body: body.map(|e| Box::new(self.fold_expr(*e))) }
+    }
+    fn fold_return(&mut self, r: Return) -> Return {
+        let Return { body } = r;
+        Return { body: body.map(|e| Box::new(self.fold_expr(*e))) }
+    }
 }
 
 #[inline]
@@ -539,6 +547,8 @@ pub fn or_fold_expr_kind<F: Fold + ?Sized>(folder: &mut F, kind: ExprKind) -> Ex
         ExprKind::While(w) => ExprKind::While(folder.fold_while(w)),
         ExprKind::If(i) => ExprKind::If(folder.fold_if(i)),
         ExprKind::For(f) => ExprKind::For(folder.fold_for(f)),
+        ExprKind::Break(b) => ExprKind::Break(folder.fold_break(b)),
+        ExprKind::Return(r) => ExprKind::Return(folder.fold_return(r)),
         ExprKind::Continue => ExprKind::Continue,
     }
 }

compiler/cl-ast/src/ast_visitor/visit.rs

@@ -322,6 +322,18 @@ pub trait Visit<'a>: Sized {
             self.visit_expr(body)
         }
     }
+    fn visit_break(&mut self, b: &'a Break) {
+        let Break { body } = b;
+        if let Some(body) = body {
+            self.visit_expr(body)
+        }
+    }
+    fn visit_return(&mut self, r: &'a Return) {
+        let Return { body } = r;
+        if let Some(body) = body {
+            self.visit_expr(body)
+        }
+    }
     fn visit_continue(&mut self) {}
 }
 
@@ -461,6 +473,8 @@ pub fn or_visit_expr_kind<'a, V: Visit<'a>>(visitor: &mut V, e: &'a ExprKind) {
         ExprKind::While(w) => visitor.visit_while(w),
         ExprKind::If(i) => visitor.visit_if(i),
         ExprKind::For(f) => visitor.visit_for(f),
+        ExprKind::Break(b) => visitor.visit_break(b),
+        ExprKind::Return(r) => visitor.visit_return(r),
         ExprKind::Continue => visitor.visit_continue(),
     }
 }

compiler/cl-ast/src/desugar/while_else.rs

@@ -21,12 +21,9 @@ fn desugar_while(extents: Span, kind: ExprKind) -> ExprKind {
     match kind {
         // work backwards: fail -> break -> if -> loop
         ExprKind::While(While { cond, pass, fail: Else { body } }) => {
-            let Expr { extents, kind } = body
-                .map(|b| *b)
-                .unwrap_or(Expr { extents, kind: ExprKind::Empty });
             // Preserve the else-expression's extents, if present, or use the parent's extents
-            let kind = ExprKind::Unary(Unary { kind: UnaryKind::Break, tail: kind.into() });
+            let fail_span = body.as_ref().map(|body| body.extents).unwrap_or(extents);
-            let break_expr = Expr { extents, kind };
+            let break_expr = Expr { extents: fail_span, kind: ExprKind::Break(Break { body }) };
 
             let loop_body = If { cond, pass, fail: Else { body: Some(Box::new(break_expr)) } };
             let loop_body = ExprKind::If(loop_body);

compiler/cl-interpret/src/interpret.rs

@@ -154,6 +154,8 @@ impl Interpret for ExprKind {
             ExprKind::While(v) => v.interpret(env),
             ExprKind::If(v) => v.interpret(env),
             ExprKind::For(v) => v.interpret(env),
+            ExprKind::Break(v) => v.interpret(env),
+            ExprKind::Return(v) => v.interpret(env),
             ExprKind::Continue => Err(Error::Continue),
         }
     }
@@ -328,8 +330,6 @@ impl Interpret for Unary {
                     e => e?,
                 };
             },
-            UnaryKind::Break => Err(Error::Break(tail.interpret(env)?)),
-            UnaryKind::Return => Err(Error::Return(tail.interpret(env)?)),
             UnaryKind::Deref => {
                 let operand = tail.interpret(env)?;
                 env.call("deref".into(), &[operand])
@@ -579,3 +579,23 @@ impl Interpret for Else {
         }
     }
 }
+impl Interpret for Return {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        Err(Error::Return(
+            body.as_ref()
+                .map(|body| body.interpret(env))
+                .unwrap_or(Ok(ConValue::Empty))?,
+        ))
+    }
+}
+impl Interpret for Break {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        let Self { body } = self;
+        Err(Error::Break(
+            body.as_ref()
+                .map(|body| body.interpret(env))
+                .unwrap_or(Ok(ConValue::Empty))?,
+        ))
+    }
+}

compiler/cl-parser/src/parser.rs

@@ -836,7 +836,6 @@ impl<'t> Parser<'t> {
         let parsing = Parsing::ExprKind;
         // Prefix expressions
         let mut head = match self.peek_kind(Parsing::Unary)? {
-            TokenKind::Semi => return Ok(ExprKind::Empty), // TODO: is this okay?
             literal_like!() => self.literal()?.into(),
             path_like!() => self.exprkind_pathlike()?,
             TokenKind::Amp | TokenKind::AmpAmp => self.addrof()?.into(),
@@ -847,6 +846,8 @@ impl<'t> Parser<'t> {
             TokenKind::While => ExprKind::While(self.parse_while()?),
             TokenKind::If => ExprKind::If(self.parse_if()?),
             TokenKind::For => ExprKind::For(self.parse_for()?),
+            TokenKind::Break => ExprKind::Break(self.parse_break()?),
+            TokenKind::Return => ExprKind::Return(self.parse_return()?),
             TokenKind::Continue => {
                 self.consume_peeked();
                 ExprKind::Continue
@@ -1158,6 +1159,24 @@ impl<'t> Parser<'t> {
 }
 /// ## Control flow subexpressions
 impl<'t> Parser<'t> {
+    /// [Break] = `break` (*unconsumed* `;` | [Expr])
+    pub fn parse_break(&mut self) -> PResult<Break> {
+        self.consume_peeked();
+        Ok(Break { body: self.ret_body(Parsing::Break)? })
+    }
+    /// [Return] = `return` (*unconsumed* `;` | [Expr])
+    pub fn parse_return(&mut self) -> PResult<Return> {
+        self.consume_peeked();
+        Ok(Return { body: self.ret_body(Parsing::Return)? })
+    }
+    /// ret_body = (*unconsumed* `;` | [Expr])
+    fn ret_body(&mut self, while_parsing: Parsing) -> PResult<Option<Box<Expr>>> {
+        Ok(match self.peek_kind(while_parsing)? {
+            TokenKind::Semi => None,
+            _ => Some(self.expr()?.into()),
+        })
+    }
+
     /// [While] = `while` [Expr] [Block] [Else]?
     pub fn parse_while(&mut self) -> PResult<While> {
         self.consume_peeked();
@@ -1272,7 +1291,7 @@ impl From<UnaryKind> for Precedence {
     fn from(value: UnaryKind) -> Self {
         use UnaryKind as Op;
         match value {
-            Op::Loop | Op::Break | Op::Return => Precedence::Assign,
+            Op::Loop => Precedence::Assign,
             Op::Deref | Op::Neg | Op::Not | Op::At | Op::Tilde => Precedence::Unary,
         }
     }
@@ -1291,8 +1310,6 @@ macro operator($($name:ident ($takes:ident => $returns:ident) {$($t:ident => $p:
 operator! {
     from_prefix (TokenKind => UnaryKind) {
         Loop => Loop,
-        Break => Break,
-        Return => Return,
         Star => Deref,
         Minus => Neg,
         Bang => Not,

compiler/cl-repl/examples/yaml.rs

@@ -409,6 +409,8 @@ pub mod yamlify {
                 ExprKind::While(k) => k.yaml(y),
                 ExprKind::If(k) => k.yaml(y),
                 ExprKind::For(k) => k.yaml(y),
+                ExprKind::Break(k) => k.yaml(y),
+                ExprKind::Return(k) => k.yaml(y),
                 ExprKind::Continue => {
                     y.key("Continue");
                 }
@@ -567,6 +569,18 @@ pub mod yamlify {
                 .yaml(fail);
         }
     }
+    impl Yamlify for Break {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("Break").yaml(body);
+        }
+    }
+    impl Yamlify for Return {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { body } = self;
+            y.key("Return").yaml(body);
+        }
+    }
     impl Yamlify for Literal {
         fn yaml(&self, y: &mut Yamler) {
             y.value(format_args!("\"{self}\""));