Small improvements ♻

src/eval/mod.rs

@@ -270,8 +270,8 @@ impl Spanned<&ExprBinary> {
 
         // Short-circuit boolean operations.
         match (self.v.op.v, &lhs) {
-            (BinOp::And, Value::Bool(false)) => return Value::Bool(false),
+            (BinOp::And, Value::Bool(false)) => return lhs,
-            (BinOp::Or, Value::Bool(true)) => return Value::Bool(true),
+            (BinOp::Or, Value::Bool(true)) => return lhs,
             _ => {}
         }
 
@@ -310,13 +310,11 @@ impl Spanned<&ExprBinary> {
                 let lhs = std::mem::replace(slot, Value::None);
                 *slot = op(lhs, rhs);
                 return Value::None;
-            } else {
+            } else if ctx.scopes.is_const(id) {
-                if ctx.scopes.is_const(id) {
                 ctx.diag(error!(span, "cannot assign to constant"));
             } else {
                 ctx.diag(error!(span, "unknown variable"));
             }
-            }
         } else {
             ctx.diag(error!(span, "cannot assign to this expression"));
         }

src/parse/mod.rs

@@ -380,42 +380,50 @@ fn stmt_let(p: &mut Parser) -> Option<Expr> {
     p.start_group(Group::Stmt, TokenMode::Code);
     p.eat_assert(Token::Let);
 
-    let pat = p.span_if(ident);
+    let pat = match p.span_if(ident) {
-    let mut rhs = None;
+        Some(pat) => pat,
-
+        None => {
-    if pat.is_some() {
+            p.expected("identifier");
-        if p.eat_if(Token::Eq) {
+            p.end_group();
-            rhs = p.span_if(expr);
+            return None;
         }
+    };
+
+    let rhs = if p.eat_if(Token::Eq) { p.span_if(expr) } else { None };
 
     if !p.eof() {
         p.expected_at("semicolon or line break", p.last_end());
     }
-    } else {
-        p.expected("identifier");
-    }
 
     p.end_group();
 
-    Some(Expr::Let(ExprLet { pat: pat?, expr: rhs.map(Box::new) }))
+    Some(Expr::Let(ExprLet { pat, expr: rhs.map(Box::new) }))
 }
 
 /// Parse an if expresion.
 fn expr_if(p: &mut Parser) -> Option<Expr> {
     p.start_group(Group::Expr, TokenMode::Code);
     p.eat_assert(Token::If);
-    let condition = p.span_if(expr);
+
+    let condition = match p.span_if(expr) {
+        Some(condition) => Box::new(condition),
+        None => {
+            p.end_group();
+            return None;
+        }
+    };
+
     p.end_group();
 
-    let condition = Box::new(condition?);
     let if_body = Box::new(control_body(p)?);
-    let end = p.last_end();
+
+    let start = p.last_end();
     p.skip_white();
 
     let else_body = if p.eat_if(Token::Else) {
         control_body(p).map(Box::new)
     } else {
-        p.jump(end);
+        p.jump(start);
         None
     };
 

src/parse/tokens.rs

@@ -127,7 +127,6 @@ impl<'s> Iterator for Tokens<'s> {
                 '=' => Token::Eq,
                 '<' => Token::Lt,
                 '>' => Token::Gt,
-                '?' => Token::Question,
 
                 // Identifiers.
                 c if is_id_start(c) => self.ident(start),
@@ -206,7 +205,6 @@ impl<'s> Tokens<'s> {
                 "#if" => Token::If,
                 "#else" => Token::Else,
                 "#for" => Token::For,
-                "#in" => Token::In,
                 "#while" => Token::While,
                 "#break" => Token::Break,
                 "#continue" => Token::Continue,
@@ -612,7 +610,6 @@ mod tests {
         t!(Code: "-="       => HyphEq);
         t!(Code: "*="       => StarEq);
         t!(Code: "/="       => SlashEq);
-        t!(Code: "?"        => Question);
         t!(Code: ".."       => Dots);
         t!(Code: "=>"       => Arrow);
 
@@ -636,7 +633,6 @@ mod tests {
             ("if", If),
             ("else", Else),
             ("for", For),
-            ("in", In),
             ("while", While),
             ("break", Break),
             ("continue", Continue),
@@ -654,6 +650,7 @@ mod tests {
             ("not", Not),
             ("and", And),
             ("or", Or),
+            ("in", In),
             ("none", Token::None),
             ("false", Bool(false)),
             ("true", Bool(true)),

src/syntax/token.rs

@@ -61,8 +61,6 @@ pub enum Token<'s> {
     StarEq,
     /// A slash followed by an equals sign: `/=`.
     SlashEq,
-    /// A question mark: `?`.
-    Question,
     /// Two dots: `..`.
     Dots,
     /// An equals sign followed by a greater-than sign: `=>`.
@@ -212,30 +210,29 @@ impl<'s> Token<'s> {
             Self::Eq => "assignment operator",
             Self::EqEq => "equality operator",
             Self::BangEq => "inequality operator",
-            Self::Lt => "less than operator",
+            Self::Lt => "less-than operator",
-            Self::LtEq => "less than or equal operator",
+            Self::LtEq => "less-than or equal operator",
-            Self::Gt => "greater than operator",
+            Self::Gt => "greater-than operator",
-            Self::GtEq => "greater than or equal operator",
+            Self::GtEq => "greater-than or equal operator",
             Self::PlusEq => "add-assign operator",
             Self::HyphEq => "subtract-assign operator",
             Self::StarEq => "multiply-assign operator",
             Self::SlashEq => "divide-assign operator",
-            Self::Question => "question mark",
             Self::Dots => "dots",
             Self::Arrow => "arrow",
-            Self::Not => "not operator",
+            Self::Not => "operator `not`",
-            Self::And => "and operator",
+            Self::And => "operator `and`",
-            Self::Or => "or operator",
+            Self::Or => "operator `or`",
-            Self::Let => "let keyword",
+            Self::Let => "keyword `let`",
-            Self::If => "if keyword",
+            Self::If => "keyword `if`",
-            Self::Else => "else keyword",
+            Self::Else => "keyword `else`",
-            Self::For => "for keyword",
+            Self::For => "keyword `for`",
-            Self::In => "in keyword",
+            Self::In => "keyword `in`",
-            Self::While => "while keyword",
+            Self::While => "keyword `while`",
-            Self::Break => "break keyword",
+            Self::Break => "keyword `break`",
-            Self::Continue => "continue keyword",
+            Self::Continue => "keyword `continue`",
-            Self::Return => "return keyword",
+            Self::Return => "keyword `return`",
-            Self::None => "none",
+            Self::None => "`none`",
             Self::Space(_) => "space",
             Self::Text(_) => "text",
             Self::Raw(_) => "raw block",

tests/lang/typ/if.typ

@@ -18,7 +18,7 @@
     "Fi" + "ve"
 }
 
-// Spacing is somewhat delicated. We only want to have spacing in the output if
+// Spacing is somewhat delicate. We only want to have spacing in the output if
 // there was whitespace before/after the full if-else statement. In particular,
 // spacing after a simple if should be retained, but spacing between the first
 // body and the else should be ignored.
@@ -53,7 +53,7 @@ a#if true {}
 a#if true [b] #else c
 
 // Lone else.
-// Error: 2:1-2:6 unexpected else keyword
+// Error: 2:1-2:6 unexpected keyword `else`
 // Error: 1:8-1:8 expected function name
 #else []
 

tests/lang/typ/let.typ

@@ -28,11 +28,15 @@
 // Error: 1:6-1:7 expected identifier, found integer
 #let 1 = 2
 
-// Terminated by end of line before binding name.
+// Missing binding name.
 // Error: 1:5-1:5 expected identifier
 #let
 x = 5
 
+// Missing right-hand side.
+// Error: 1:9-1:9 expected expression
+#let a =
+
 // No name at all.
 // Error: 1:11-1:11 expected identifier
 The Fi#let;rst

tests/typeset.rs

@@ -254,7 +254,7 @@ fn parse_metadata(src: &str, map: &LineMap) -> (bool, SpanVec<Diag>) {
         let pos = |s: &mut Scanner| -> Pos {
             let (delta, _, column) = (num(s), s.eat_assert(':'), num(s));
             let line = i as u32 + 1 + delta;
-            map.pos(Location { line, column }).unwrap()
+            map.pos(Location::new(line, column)).unwrap()
         };
 
         let mut s = Scanner::new(rest);