Blocks and conditionals.

src/syntax.rs

@@ -110,13 +110,14 @@ pub enum ExportClass {
 #[derive(Debug)]
 pub enum Statement {
     Binding(BindingStmt),
+    Expression(Expression),
 }
 
 #[derive(Debug)]
 pub struct BindingStmt {
     location: Location,
     mutable: bool,
-    variable: String,
+    variable: Name,
     value: Expression,
 }
 
@@ -126,7 +127,17 @@ pub enum Expression {
     Reference(Name),
     EnumerationValue(Name, Name, Option<Box<Expression>>),
     StructureValue(Name, Vec<FieldValue>),
+    Conditional(ConditionalExpr),
     Call(Box<Expression>, CallKind, Vec<Expression>),
+    Block(Location, Vec<Statement>),
+}
+
+#[derive(Debug)]
+pub struct ConditionalExpr {
+    location: Location,
+    test: Box<Expression>,
+    consequent: Box<Expression>,
+    alternative: Option<Box<Expression>>,
 }
 
 #[derive(Debug)]

src/syntax/name.rs

@@ -1,4 +1,4 @@
-use crate::syntax::{Located, Location};
+use crate::syntax::Location;
 use std::cmp;
 use std::fmt;
 use std::hash;

src/syntax/parse.rs

@@ -7,7 +7,9 @@ pub struct Parser<'a> {
     file_id: usize,
     lexer: Lexer<'a>,
     known_tokens: Vec<LocatedToken>,
-    precedence_table: HashMap<String, (u8, u8)>,
+    prefix_precedence_table: HashMap<String, u8>,
+    infix_precedence_table: HashMap<String, (u8, u8)>,
+    postfix_precedence_table: HashMap<String, u8>,
 }
 
 pub enum Associativity {
@@ -28,7 +30,9 @@ impl<'a> Parser<'a> {
             file_id,
             lexer,
             known_tokens: vec![],
-            precedence_table: HashMap::new(),
+            prefix_precedence_table: HashMap::new(),
+            infix_precedence_table: HashMap::new(),
+            postfix_precedence_table: HashMap::new(),
         }
     }
 
@@ -38,7 +42,7 @@ impl<'a> Parser<'a> {
         &mut self,
         operator: S,
         associativity: Associativity,
-        level: u8
+        level: u8,
     ) {
         let actual_associativity = match associativity {
             Associativity::Left => (level * 2, (level * 2) + 1),
@@ -46,11 +50,22 @@ impl<'a> Parser<'a> {
             Associativity::None => (level * 2, level * 2),
         };
 
-        self.precedence_table.insert(operator.to_string(), actual_associativity);
+        self.infix_precedence_table
+            .insert(operator.to_string(), actual_associativity);
+    }
+
+    pub fn add_prefix_precedence<S: ToString>(&mut self, operator: S, level: u8) {
+        self.prefix_precedence_table
+            .insert(operator.to_string(), level * 2);
+    }
+
+    pub fn add_postfix_precedence<S: ToString>(&mut self, operator: S, level: u8) {
+        self.postfix_precedence_table
+            .insert(operator.to_string(), level * 2);
     }
 
     fn get_precedence(&self, name: &String) -> (u8, u8) {
-        match self.precedence_table.get(name) {
+        match self.infix_precedence_table.get(name) {
             None => (19, 20),
             Some(x) => *x,
         }
@@ -588,14 +603,17 @@ impl<'a> Parser<'a> {
     }
 
     pub fn parse_expression(&mut self) -> Result<Expression, ParserError> {
-        let next = self.next()?.ok_or_else(||
-            self.bad_eof("looking for an expression"))?;
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for an expression"))?;
 
         self.save(next.clone());
         match next.token {
             Token::ValueName(x) if x == "match" => self.parse_match_expression(),
-            Token::ValueName(x) if x == "if" => self.parse_if_expression(),
-            _ => self.parse_infix(0),
+            Token::ValueName(x) if x == "if" => {
+                Ok(Expression::Conditional(self.parse_if_expression()?))
+            }
+            _ => self.parse_arithmetic(0),
         }
     }
 
@@ -603,12 +621,244 @@ impl<'a> Parser<'a> {
         unimplemented!()
     }
 
-    pub fn parse_if_expression(&mut self) -> Result<Expression, ParserError> {
-        unimplemented!()
+    pub fn parse_if_expression(&mut self) -> Result<ConditionalExpr, ParserError> {
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for an 'if' to start conditional"))?;
+        if !matches!(next.token, Token::ValueName(ref x) if x == "if") {
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "an 'if' to start a conditional",
+            });
+        }
+        let start = self.to_location(next.span);
+
+        let test = self.parse_arithmetic(0)?;
+        let consequent = self.parse_block()?;
+
+        let maybe_else = self.next()?;
+        let (alternative, location) = match maybe_else {
+            Some(LocatedToken {
+                token: Token::ValueName(ref n),
+                ..
+            }) if n == "else" => {
+                let expr = self.parse_block()?;
+                let location = match expr {
+                    Expression::Block(ref l, _) => l.clone(),
+                    _ => panic!("How did parse_block not return a block?!"),
+                };
+
+                (Some(Box::new(expr)), location)
             }
 
-    pub fn parse_infix(&mut self, level: u8) -> Result<Expression, ParserError> {
-        let mut lhs = self.parse_base_expression()?;
+            _ => {
+                let location = match consequent {
+                    Expression::Block(ref l, _) => l.clone(),
+                    _ => panic!("How did parse_block not return a block?!"),
+                };
+
+                (None, location)
+            }
+        };
+
+        Ok(ConditionalExpr {
+            location,
+            test: Box::new(test),
+            consequent: Box::new(consequent),
+            alternative,
+        })
+    }
+
+    pub fn parse_block(&mut self) -> Result<Expression, ParserError> {
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for open brace to start block"))?;
+        if !matches!(next.token, Token::OpenBrace) {
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "an open brace to start a block",
+            });
+        }
+        let start = self.to_location(next.span);
+
+        let mut statements = vec![];
+        let mut ended_with_expr = false;
+
+        while let Some((stmt, terminal)) = self.parse_statement()? {
+            statements.push(stmt);
+            if terminal {
+                ended_with_expr = true;
+                break;
+            }
+        }
+
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for statement or block close"))?;
+        if !matches!(next.token, Token::CloseBrace) {
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "a close brace to end a block",
+            });
+        }
+        let end = self.to_location(next.span);
+
+        if !ended_with_expr {
+            let void_name = Name::new(end.clone(), "%prim%void");
+            let void_ref = Expression::Reference(void_name);
+            let void_call = Expression::Call(Box::new(void_ref), CallKind::Normal, vec![]);
+            statements.push(Statement::Expression(void_call));
+        }
+
+        Ok(Expression::Block(start.extend_to(&end), statements))
+    }
+
+    pub fn parse_statement(&mut self) -> Result<Option<(Statement, bool)>, ParserError> {
+        loop {
+            let next = self
+                .next()?
+                .ok_or_else(|| self.bad_eof("looking for a statement or close brace"))?;
+
+            match next.token {
+                Token::CloseBrace => {
+                    self.save(next);
+                    return Ok(None);
+                }
+
+                Token::ValueName(ref l) if l == "let" => {
+                    self.save(next);
+                    return Ok(Some((Statement::Binding(self.parse_let()?), false)));
+                }
+
+                _ => {
+                    self.save(next);
+                    let expr = Statement::Expression(self.parse_expression()?);
+
+                    let next = self
+                        .next()?
+                        .ok_or_else(|| self.bad_eof("looking for semicolon or close brace"))?;
+
+                    if matches!(next.token, Token::Semi) {
+                        return Ok(Some((expr, false)));
+                    } else {
+                        self.save(next);
+                        return Ok(Some((expr, true)));
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn parse_let(&mut self) -> Result<BindingStmt, ParserError> {
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for a let for a binding statement"))?;
+        if !matches!(next.token, Token::ValueName(ref n) if n == "let") {
+            self.save(next.clone());
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "a 'let' to open a binding statement",
+            });
+        }
+        let start = self.to_location(next.span);
+
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("'mut' or a variable name"))?;
+        let mutable = matches!(next.token, Token::ValueName(ref n) if n == "mut");
+        if !mutable {
+            self.save(next);
+        }
+
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("a variable name"))?;
+        let variable = match next.token {
+            Token::ValueName(v) => Name::new(self.to_location(next.span), v),
+            _ => {
+                return Err(ParserError::UnexpectedToken {
+                    file_id: self.file_id,
+                    span: next.span,
+                    token: next.token,
+                    expected: "a variable name for the let binding",
+                });
+            }
+        };
+
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("an '=' after a variable name in a binding"))?;
+        if !matches!(next.token, Token::OperatorName(ref x) if x == "=") {
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "an '=' after the variable name in a let binding",
+            });
+        }
+
+        let value = self.parse_expression()?;
+
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for terminal semicolon for let statement"))?;
+        if !matches!(next.token, Token::Semi) {
+            return Err(ParserError::UnexpectedToken {
+                file_id: self.file_id,
+                span: next.span,
+                token: next.token,
+                expected: "a semicolon to finish a let statement",
+            });
+        }
+        let end = self.to_location(next.span);
+
+        Ok(BindingStmt {
+            location: start.extend_to(&end),
+            mutable,
+            variable,
+            value,
+        })
+    }
+
+    pub fn parse_arithmetic(&mut self, level: u8) -> Result<Expression, ParserError> {
+        // start by checking for prefix operators.
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for arithmetic expression"))?;
+
+        let mut lhs = if let Token::OperatorName(ref n) = next.token {
+            if let Some(pre_prec) = self.prefix_precedence_table.get(n) {
+                if *pre_prec < level {
+                    self.save(next.clone());
+                    return Err(ParserError::UnexpectedToken {
+                        file_id: self.file_id,
+                        span: next.span,
+                        token: next.token,
+                        expected: "a base expression of a tighter-binding prefix operator",
+                    });
+                }
+
+                let rhs = self.parse_arithmetic(*pre_prec)?;
+                let opname = Name::new(self.to_location(next.span), n);
+                let op_expr = Expression::Reference(opname);
+
+                Expression::Call(Box::new(op_expr), CallKind::Prefix, vec![rhs])
+            } else {
+                self.save(next);
+                self.parse_base_expression()?
+            }
+        } else {
+            self.save(next);
+            self.parse_base_expression()?
+        };
 
         loop {
             let Some(next) = self.next()? else {
@@ -621,7 +871,21 @@ impl<'a> Parser<'a> {
                     let args = self.parse_call_arguments()?;
                     lhs = Expression::Call(Box::new(lhs), CallKind::Normal, args);
                 }
+
                 Token::OperatorName(ref n) => {
+                    if let Some(postprec) = self.postfix_precedence_table.get(n) {
+                        if *postprec < level {
+                            self.save(next);
+                            break;
+                        }
+
+                        let opname = Name::new(self.to_location(next.span), n);
+                        let op_expr = Expression::Reference(opname);
+
+                        lhs = Expression::Call(Box::new(op_expr), CallKind::Postfix, vec![lhs]);
+                        continue;
+                    }
+
                     let (left_pr, right_pr) = self.get_precedence(&n);
 
                     if left_pr < level {
@@ -629,13 +893,14 @@ impl<'a> Parser<'a> {
                         break;
                     }
 
-                    let rhs = self.parse_infix(right_pr)?;
+                    let rhs = self.parse_arithmetic(right_pr)?;
                     let name = Name::new(self.to_location(next.span), n);
                     let opref = Box::new(Expression::Reference(name));
                     let args = vec![lhs, rhs];
 
                     lhs = Expression::Call(opref, CallKind::Infix, args);
                 }
+
                 _ => {
                     self.save(next);
                     return Ok(lhs);
@@ -647,8 +912,9 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_call_arguments(&mut self) -> Result<Vec<Expression>, ParserError> {
-        let next = self.next()?.ok_or_else(|| self.bad_eof(
-          "looking for open paren for function arguments"))?;
+        let next = self
+            .next()?
+            .ok_or_else(|| self.bad_eof("looking for open paren for function arguments"))?;
 
         if !matches!(next.token, Token::OpenParen) {
             return Err(ParserError::UnexpectedToken {
@@ -662,28 +928,32 @@ impl<'a> Parser<'a> {
         let mut args = vec![];
 
         loop {
-            let next = self.next()?.ok_or_else(|| self.bad_eof(
-              "looking for an expression or close paren in function arguments"))?;
+            let next = self.next()?.ok_or_else(|| {
+                self.bad_eof("looking for an expression or close paren in function arguments")
+            })?;
 
             if matches!(next.token, Token::CloseParen) {
                 break;
             }
 
             self.save(next);
-            let argument = self.parse_infix(0)?;
+            let argument = self.parse_arithmetic(0)?;
             args.push(argument);
 
-            let next = self.next()?.ok_or_else(|| self.bad_eof(
-              "looking for comma or close paren in function arguments"))?;
+            let next = self.next()?.ok_or_else(|| {
+                self.bad_eof("looking for comma or close paren in function arguments")
+            })?;
             match next.token {
                 Token::Comma => continue,
                 Token::CloseParen => break,
-                _ => return Err(ParserError::UnexpectedToken {
+                _ => {
+                    return Err(ParserError::UnexpectedToken {
                         file_id: self.file_id,
                         span: next.span,
                         token: next.token,
                         expected: "comma or close paren in function arguments",
-                }),
+                    });
+                }
             }
         }
 
@@ -700,7 +970,10 @@ impl<'a> Parser<'a> {
             .ok_or_else(|| self.bad_eof("looking for an expression"))?;
 
         match next.token {
-            Token::OpenBrace => unimplemented!(),
+            Token::OpenBrace => {
+                self.save(next);
+                return self.parse_block();
+            }
 
             Token::OpenParen => {
                 let inner = self.parse_expression()?;

src/syntax/parser_tests.rs

@@ -1,5 +1,6 @@
+use crate::syntax::error::ParserError;
 use crate::syntax::parse::Parser;
-use crate::syntax::tokens::Lexer;
+use crate::syntax::tokens::{Lexer, Token};
 use crate::syntax::*;
 
 #[test]
@@ -513,9 +514,7 @@ fn structure_value() {
                 f2.as_printed() == "bar" &&
                 matches!(v1, Expression::Value(ConstantValue::Integer(_,_))) &&
                 matches!(v2, Expression::Value(ConstantValue::String(_,_))))));
-    assert!(matches!(
-      parse_st("Foo{ foo: 1,, bar: \"foo\", }"),
-      Err(_)));
+    assert!(matches!(parse_st("Foo{ foo: 1,, bar: \"foo\", }"), Err(_)));
 }
 
 #[test]
@@ -528,7 +527,6 @@ fn infix_and_precedence() {
         result.parse_expression()
     };
 
-
     assert!(matches!(
       parse_ex("0"),
       Ok(Expression::Value(ConstantValue::Integer(_, IntegerWithBase{ value, .. })))
@@ -659,15 +657,9 @@ fn calls() {
           Expression::Reference(a),
           Expression::Reference(b),
         ] if a.as_printed() == "a" && b.as_printed() == "b")));
-    assert!(matches!(
-      parse_ex("f(,a,b,)"),
-      Err(_)));
-    assert!(matches!(
-      parse_ex("f(a,,b,)"),
-      Err(_)));
-    assert!(matches!(
-      parse_ex("f(a,b,,)"),
-      Err(_)));
+    assert!(matches!(parse_ex("f(,a,b,)"), Err(_)));
+    assert!(matches!(parse_ex("f(a,,b,)"), Err(_)));
+    assert!(matches!(parse_ex("f(a,b,,)"), Err(_)));
 
     assert!(matches!(
       parse_ex("f()()"),
@@ -769,3 +761,170 @@ fn calls() {
          Expression::Value(ConstantValue::Integer(_, IntegerWithBase{ value: 3, .. }))
        ]))))));
 }
+
+#[test]
+fn prefix_and_postfix() {
+    let parse_ex = |str| {
+        let lexer = Lexer::from(str);
+        let mut result = Parser::new(0, lexer);
+        result.add_infix_precedence("+", parse::Associativity::Left, 4);
+        result.add_infix_precedence("*", parse::Associativity::Left, 8);
+        result.add_prefix_precedence("++", 6);
+        result.add_postfix_precedence("++", 6);
+        result.add_prefix_precedence("--", 7);
+        result.add_postfix_precedence("--", 7);
+        result.parse_expression()
+    };
+
+    assert!(matches!(
+     parse_ex("++a"),
+     Ok(Expression::Call(pp, CallKind::Prefix, args)) if
+      matches!(pp.as_ref(), Expression::Reference(n) if n.as_printed() == "++") &&
+      matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "a")));
+
+    assert!(matches!(
+     parse_ex("a--"),
+     Ok(Expression::Call(pp, CallKind::Postfix, args)) if
+      matches!(pp.as_ref(), Expression::Reference(n) if n.as_printed() == "--") &&
+      matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "a")));
+
+    // the prefix is weaker than the postfix, so it should be the outside
+    // operatotr
+    assert!(matches!(
+     parse_ex("++a--"),
+     Ok(Expression::Call(pp, CallKind::Prefix, args)) if
+      matches!(pp.as_ref(), Expression::Reference(n) if n.as_printed() == "++") &&
+      matches!(args.as_slice(), [Expression::Call(mm, CallKind::Postfix, args)] if
+        matches!(mm.as_ref(), Expression::Reference(n) if n.as_printed() == "--") &&
+        matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "a"))));
+
+    // the prefix is stronger than the postfix, so it should be the inside
+    // operator
+    assert!(matches!(
+     parse_ex("--a++"),
+     Ok(Expression::Call(pp, CallKind::Postfix, args)) if
+      matches!(pp.as_ref(), Expression::Reference(n) if n.as_printed() == "++") &&
+      matches!(args.as_slice(), [Expression::Call(mm, CallKind::Prefix, args)] if
+        matches!(mm.as_ref(), Expression::Reference(n) if n.as_printed() == "--") &&
+        matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "a"))));
+
+    assert!(matches!(
+     parse_ex("a++ + b"),
+     Ok(Expression::Call(p, CallKind::Infix, args)) if
+      matches!(p.as_ref(), Expression::Reference(n) if n.as_printed() == "+") &&
+      matches!(args.as_slice(), [
+        Expression::Call(mm, CallKind::Postfix, args),
+        Expression::Reference(n)
+      ] if n.as_printed() == "b" &&
+        matches!(mm.as_ref(), Expression::Reference(n) if n.as_printed() == "++") &&
+        matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "a"))));
+
+    assert!(matches!(
+     parse_ex("a + ++ b"),
+     Ok(Expression::Call(p, CallKind::Infix, args)) if
+      matches!(p.as_ref(), Expression::Reference(n) if n.as_printed() == "+") &&
+      matches!(args.as_slice(), [
+        Expression::Reference(n),
+        Expression::Call(mm, CallKind::Prefix, args),
+      ] if n.as_printed() == "a" &&
+        matches!(mm.as_ref(), Expression::Reference(n) if n.as_printed() == "++") &&
+        matches!(args.as_slice(), [Expression::Reference(n)] if n.as_printed() == "b"))));
+
+    assert!(matches!(
+     parse_ex("a * ++ b"),
+     Err(ParserError::UnexpectedToken{ token: Token::OperatorName(pp), .. })
+      if pp == "++"));
+}
+
+#[test]
+fn blocks() {
+    let parse_ex = |str| {
+        let lexer = Lexer::from(str);
+        let mut result = Parser::new(0, lexer);
+        result.parse_expression()
+    };
+
+    assert!(matches!(
+     parse_ex("{}"),
+     Ok(Expression::Block(_, void)) if
+      matches!(void.as_slice(), [Statement::Expression(call)] if
+       matches!(call, Expression::Call(void, CallKind::Normal, vargs) if
+        matches!(void.as_ref(), Expression::Reference(n) if
+          n.as_printed() == "%prim%void") &&
+        vargs.is_empty()))));
+    assert!(matches!(
+     parse_ex("{ x }"),
+     Ok(Expression::Block(_, x)) if
+      matches!(x.as_slice(), [Statement::Expression(Expression::Reference(n))] if
+       n.as_printed() == "x")));
+    assert!(matches!(
+     parse_ex("{ x; }"),
+     Ok(Expression::Block(_, x)) if
+      matches!(x.as_slice(), [
+        Statement::Expression(Expression::Reference(n)),
+        Statement::Expression(Expression::Call(primv, CallKind::Normal, vargs)),
+      ] if n.as_printed() == "x" && vargs.is_empty() &&
+       matches!(primv.as_ref(), Expression::Reference(n) if
+        n.as_printed() == "%prim%void"))));
+    assert!(matches!(
+     parse_ex("{ x; y }"),
+     Ok(Expression::Block(_, x)) if
+      matches!(x.as_slice(), [
+        Statement::Expression(Expression::Reference(x)),
+        Statement::Expression(Expression::Reference(y)),
+      ] if x.as_printed() == "x" && y.as_printed() == "y")));
+}
+
+#[test]
+fn bindings() {
+    let parse_ex = |str| {
+        let lexer = Lexer::from(str);
+        let mut result = Parser::new(0, lexer);
+        result.parse_expression()
+    };
+
+    assert!(matches!(
+     parse_ex("{ let x = y; }"),
+     Ok(Expression::Block(_, x)) if
+      matches!(x.as_slice(), [Statement::Binding(b), Statement::Expression(_)] if
+       !b.mutable &&
+       b.variable.as_printed() == "x" &&
+       matches!(b.value, Expression::Reference(ref n) if n.as_printed() == "y"))));
+}
+
+#[test]
+fn conditionals() {
+    let parse_ex = |str| {
+        let lexer = Lexer::from(str);
+        let mut result = Parser::new(0, lexer);
+        result.parse_expression()
+    };
+
+    assert!(matches!(
+     parse_ex("if x { y } else { z }"),
+     Ok(Expression::Conditional(cond)) if
+      matches!(cond.test.as_ref(), Expression::Reference(n) if n.as_printed() == "x") &&
+      matches!(cond.consequent.as_ref(), Expression::Block(_, cs) if
+       matches!(cs.as_slice(), [Statement::Expression(Expression::Reference(n))] if
+        n.as_printed() == "y")) &&
+      matches!(cond.alternative.as_ref(), Some(expr) if
+       matches!(expr.as_ref(), Expression::Block(_, ast) if
+        matches!(ast.as_slice(), [Statement::Expression(Expression::Reference(n))] if
+         n.as_printed() == "z")))));
+
+    assert!(matches!(
+     parse_ex("if x { y }"),
+     Ok(Expression::Conditional(cond)) if
+      matches!(cond.test.as_ref(), Expression::Reference(n) if n.as_printed() == "x") &&
+      matches!(cond.consequent.as_ref(), Expression::Block(_, cs) if
+       matches!(cs.as_slice(), [Statement::Expression(Expression::Reference(n))] if
+        n.as_printed() == "y")) &&
+       cond.alternative.is_none()));
+
+    assert!(matches!(parse_ex("if x v { z }"), Err(_)));
+
+    assert!(matches!(
+     parse_ex("if x + y { z }"),
+     Ok(Expression::Conditional(cond)) if
+      matches!(cond.test.as_ref(), Expression::Call(_, CallKind::Infix, _))));
+}

src/syntax/tokens.rs

@@ -476,10 +476,33 @@ impl<'a> LexerState<'a> {
                 token: Token::OperatorName("-".into()),
                 span: token_start_offset..token_start_offset + 1,
             })),
-            Some((end, '>')) => Ok(Some(LocatedToken {
+            Some((end, '>')) => {
+                let Some((pbloc, peekaboo)) = self.next_char() else {
+                    return Ok(Some(LocatedToken {
                         token: Token::Arrow,
                         span: token_start_offset..end,
-            })),
+                    }));
+                };
+                let is_operator = !peekaboo.is_alphanumeric()
+                    && !peekaboo.is_whitespace()
+                    && !peekaboo.is_control();
+
+                if is_operator {
+                    self.parse_identifier(
+                        token_start_offset,
+                        format!("->{peekaboo}"),
+                        |c| !c.is_alphanumeric() && !c.is_whitespace() && !c.is_control(),
+                        Token::OperatorName,
+                    )
+                } else {
+                    self.stash_char(pbloc, peekaboo);
+
+                    Ok(Some(LocatedToken {
+                        token: Token::Arrow,
+                        span: token_start_offset..end,
+                    }))
+                }
+            }
             Some((_, c)) if !c.is_alphanumeric() && !c.is_whitespace() && !c.is_control() => self
                 .parse_identifier(
                     token_start_offset,
@@ -665,3 +688,22 @@ fn can_separate_pieces() {
     assert_eq!(Some(Token::ValueName("b".into())), next_token());
     assert_eq!(None, next_token());
 }
+
+#[test]
+fn arrow_requires_nonop() {
+    let mut lexer = Lexer::from("->");
+    let mut next_token = move || lexer.next().map(|x| x.expect("Can read valid token").token);
+    assert_eq!(Some(Token::Arrow), next_token());
+
+    let mut lexer = Lexer::from("->*");
+    let mut next_token = move || lexer.next().map(|x| x.expect("Can read valid token").token);
+    assert_eq!(Some(Token::OperatorName("->*".into())), next_token());
+
+    let mut lexer = Lexer::from("->*x");
+    let mut next_token = move || lexer.next().map(|x| x.expect("Can read valid token").token);
+    assert_eq!(Some(Token::OperatorName("->*".into())), next_token());
+
+    let mut lexer = Lexer::from("->x");
+    let mut next_token = move || lexer.next().map(|x| x.expect("Can read valid token").token);
+    assert_eq!(Some(Token::Arrow), next_token());
+}