introduce symbol to indicate matching, now used on all single-arg invocations

This also merges the `match` and single-call interface.
Modules can simply be called with tags.

README.md

@@ -35,8 +35,8 @@ as an argument, prefix the block with `'`.
 ## Control flow builtins
 
 - `cflow.if, cond = ..., then = ..., else = ...`
-- `cflow.loop ...`
-- `cflow.return ...` (implicit when last expr in a block is not terminated via semicolon)
+- `cflow.loop § ...`
+- `cflow.return § ...` (implicit when last expr in a block is not terminated via semicolon)
 
 ## Modules
 
@@ -61,7 +61,7 @@ with package-lock files or such. Packages (packaged module trees) would then be
   # 1.
 
   final main { args env } = {
-    std.io.writeln "Hello World!";
+    std.io.writeln § "Hello World!";
     0
   };
 
@@ -72,7 +72,7 @@ with package-lock files or such. Packages (packaged module trees) would then be
   what_now = {
     self.business_in_the_front;
   }, self.party_in_the_back {
-    std.io.writeln "It works";
+    std.io.writeln § "It works";
   };
 
   # running `what_now` results in "It works" being printed.

crates/wafl-parser/src/lex.rs

@@ -6,7 +6,6 @@ pub enum Token<'a> {
     CtrlFlowEdit,
     Defer,
     Final,
-    Match,
     Module,
     Public,
     Tag,
@@ -15,9 +14,12 @@ pub enum Token<'a> {
     Assign,
     OpenBrace,
     CloseBrace,
+    OpenParen,
+    CloseParen,
     Comma,
     SemiColon,
     Dot,
+    MatchPara,
 
     // dynamic stuff
     /// amount of prefixed `$` to force immediate application
@@ -32,11 +34,6 @@ impl Token<'_> {
     pub fn is_def_attr(&self) -> bool {
         matches!(self, Token::Final)
     }
-
-    #[inline]
-    pub fn is_cobj_attr(&self) -> bool {
-        matches!(self, Token::CtrlFlowEdit)
-    }
 }
 
 #[derive(Clone, PartialEq, Eq)]
@@ -106,15 +103,18 @@ impl<'a> Iterator for Lexer<'a> {
             let x = self.s.chars().next()?;
             let loc = self.loc;
             let rtok = match x {
-                '{' | '}' | '=' | ',' | ';' | '.' => {
+                '{' | '}' | '(' | ')' | '=' | ',' | ';' | '.' | '§' => {
                     self.eat(x.len_utf8());
                     match x {
                         '{' => Token::OpenBrace,
                         '}' => Token::CloseBrace,
+                        '(' => Token::OpenParen,
+                        ')' => Token::CloseParen,
                         '=' => Token::Assign,
                         ',' => Token::Comma,
                         ';' => Token::SemiColon,
                         '.' => Token::Dot,
+                        '§' => Token::MatchPara,
                         _ => unreachable!(),
                     }
                 }
@@ -179,7 +179,6 @@ impl<'a> Iterator for Lexer<'a> {
                         "cfe" => Token::CtrlFlowEdit,
                         "defer" => Token::Defer,
                         "final" => Token::Final,
-                        "match" => Token::Match,
                         "module" => Token::Module,
                         "pub" => Token::Public,
                         "tag" => Token::Tag,

crates/wafl-parser/src/parser.rs

@@ -50,10 +50,7 @@ pub enum Expression {
         obj: Box<Expression>,
         args: BTreeMap<Box<[Atom]>, (Location, Expression)>,
     },
-    Tag {
-        obj: Box<Expression>,
-        args: BTreeMap<Box<[Atom]>, (Location, Expression)>,
-    },
+    Tag(Path),
 }
 
 #[derive(Clone, Debug)]
@@ -79,6 +76,7 @@ pub enum ErrorKind {
     UnexpectedTrail,
     InvalidIdentifier,
     DuplicateIdentifier,
+    InvalidCombination(&'static str),
     Unexpected(&'static str),
     Unknown,
 }
@@ -184,7 +182,10 @@ impl FullIdentifier {
 impl Expression {
     fn parse_high(ctx: &mut ParserContext<'_>) -> Result<Self, Error> {
         let mut cfe = false;
-        for (_, i) in ctx.pklx.peeking_take_while(|(_, t)| t.is_cobj_attr()) {
+        for (_, i) in ctx
+            .pklx
+            .peeking_take_while(|(_, t)| matches!(t, Token::CtrlFlowEdit))
+        {
             match i {
                 Token::CtrlFlowEdit => cfe = true,
                 _ => unimplemented!(),
@@ -224,9 +225,12 @@ impl Expression {
                 loc,
                 kind: ErrorKind::Unexpected("braced statement set"),
             }),
-            // we have no proper recursive delimiting,
-            // so just resort to the parsing which we also do for other such items,
-            // expect a single code object descriptor => alias, or number.
+            Some((_, Token::OpenParen)) => {
+                ctx.pklx.next();
+                let inner = Expression::parse_high(ctx)?;
+                ctx.expect_token(Token::CloseParen, /* ( */ ")")?;
+                Ok(inner)
+            }
             Some(&(_, Token::Integer(i))) => {
                 ctx.pklx.next();
                 Ok(Expression::Integer(i))
@@ -238,31 +242,45 @@ impl Expression {
                 ctx.expect_token(Token::CloseBrace, "}")?;
                 Ok(Expression::Module(m))
             }
+            Some((_, Token::Tag)) => {
+                ctx.pklx.next();
+                Path::parse_high(ctx).map(Expression::Tag)
+            }
             _ => FullIdentifier::parse_high(ctx).map(Expression::Alias),
         }?;
 
-        Ok(if let Some(&(_, Token::Comma)) = ctx.pklx.peek() {
-            let mut args = BTreeMap::new();
-            while ctx.maybe_eat_token(Token::Comma).is_some() {
-                let Path { loc, idents } = Path::parse_high(ctx)?;
-                ctx.expect_token(Token::Assign, "=")?;
-                let obj = Expression::parse_high(ctx)?;
-                if args.insert(idents, (loc, obj)).is_some() {
-                    return Err(Error {
-                        loc,
-                        kind: ErrorKind::DuplicateIdentifier,
-                    });
+        match ctx.pklx.peek() {
+            None | Some((_, Token::SemiColon | Token::CloseBrace | Token::CloseParen)) => Ok(obj),
+            Some((_, Token::Comma)) => {
+                let mut args = BTreeMap::new();
+                while ctx.maybe_eat_token(Token::Comma).is_some() {
+                    let Path { loc, idents } = Path::parse_high(ctx)?;
+                    ctx.expect_token(Token::Assign, "=")?;
+                    let obj = Expression::parse_high(ctx)?;
+                    if args.insert(idents, (loc, obj)).is_some() {
+                        return Err(Error {
+                            loc,
+                            kind: ErrorKind::DuplicateIdentifier,
+                        });
+                    }
                 }
+                Ok(Expression::InvocationMulti {
+                    obj: Box::new(obj),
+                    args,
+                })
             }
-            Expression::InvocationMulti {
-                obj: Box::new(obj),
-                args,
+            Some((_, Token::MatchPara)) => {
+                ctx.pklx.next();
+                Ok(Expression::InvocationSingle(Box::new((
+                    obj,
+                    Expression::parse_high(ctx)?,
+                ))))
             }
-        } else if matches!(ctx.pklx.peek(), Some(&(_, Token::SemiColon)) | None) {
-            obj
-        } else {
-            Expression::InvocationSingle(Box::new((obj, Expression::parse_high(ctx)?)))
-        })
+            _ => Err(Error {
+                loc: ctx.peek_loc(),
+                kind: ErrorKind::Unexpected("end of expression"),
+            }),
+        }
     }
 }