More syntax changes

cli/test.roc

@@ -1,64 +1,69 @@
-succeed = (val) -> Success val
+succeed = (val) ->
+  Success val
 
 
-fail = (val) -> Failure val
+fail = (val) ->
+  Failure val
 
 
-echo = (str) -> Echo str, succeed, fail
+echo = (str) ->
+  Echo str, succeed, fail
 
 
-read = Read succeed, fail
+readInput =
+  Read succeed, fail
 
 
 map = (convert, task) ->
-    await task, (output) ->
+  after task, (output) ->
     succeed (convert output)
 
 
 mapErr = (convert, task) ->
-    fallback task, (err) ->
+  fallback task, (err) ->
     fail (convert err)
 
 
-await = (task, cont) ->
-    match task
-        when Success val then cont val
-        when Failure val then Failure val
+after = (task, cont) ->
+  case task
+    when Success val then cont val
+    when Failure val then Failure val
 
-        when Echo str, prevCont, onFailure then
-            Echo str,
-                (({}) -> await (prevCont {}), cont)
-                ((ioErr) -> await (onFailure ioErr), cont)
-
-        when Read prevCont, onFailure then
-            Read
-                ((str) -> await (prevCont str), cont)
-                ((ioErr) -> await (onFailure ioErr), cont)
+    when Echo str, prevCont, onFailure then
+      Echo str,
+        ({} -> after (prevCont {}), cont),
+        (ioErr -> after (onFailure ioErr), cont)
 
+    when Read prevCont, onFailure then
+      Read
+        (str -> after (prevCont str), cont),
+        (ioErr -> after (onFailure ioErr), cont)
 
 
 fallback = (task, onFailure) ->
-    match task
-        when Success val then Success val
-        when Failure val then onFailure val
+  case task
+    when Success val then Success val
+    when Failure val then onFailure val
 
-        when Echo str, cont, prevOnFailure then
-            Echo str
-                (({}) -> fallback (cont {}), onFailure)
-                ((ioErr) -> fallback (prevOnFailure ioErr), onFailure)
+    when Echo str, cont, prevOnFailure then
+      Echo str
+        ({} -> fallback (cont {}), onFailure),
+        (ioErr -> fallback (prevOnFailure ioErr), onFailure)
 
-        when Read cont, prevOnFailure then
-            Read
-                ((str) -> fallback (cont str), onFailure)
-                ((ioErr) -> fallback (prevOnFailure ioErr), onFailure)
+    when Read cont, prevOnFailure then
+      Read
+        (str -> fallback (cont str), onFailure),
+        (ioErr -> fallback (prevOnFailure ioErr), onFailure)
 
 
 demo =
-    await (echo "Enter first name"), ({}) ->
-    await read, (firstName) ->
-    await (echo "Enter last name"), ({}) ->
-    await read, (lastName) ->
-    echo "Your name is: \(firstName) \(lastName)"
+  after (echo "Enter first name"), ({}) ->
+    after readInput, (firstName) ->
+      after (echo "Enter last name"), ({}) ->
+        after readInput, (lastName) ->
+          fullName = "\(firstName) \(lastName)"
+
+          echo "Your name is: \(fullName)"
 
 
 demo

src/eval.rs

@@ -31,7 +31,7 @@ fn problem(prob: Problem) -> Evaluated {
 pub fn scoped_eval(expr: Expr, vars: &Scope) -> Evaluated {
     match expr {
         // Primitives need no further evaluation
-        Error(_) | Int(_) | Str(_) | Frac(_, _) | Char(_) | Bool(_) | Closure(_, _) => Evaluated(expr),
+        Error(_) | Int(_) | Str(_) | Frac(_, _) | Char(_) | Bool(_) | Closure(_, _) | Expr::EmptyRecord => Evaluated(expr),
 
         // Resolve variable names
         Var(name) => match vars.get(&name) {
@@ -72,6 +72,14 @@ pub fn scoped_eval(expr: Expr, vars: &Scope) -> Evaluated {
             scoped_eval(*in_expr, vars)
         },
 
+        Let(Pattern::EmptyRecord, definition, in_expr) => {
+            // Faithfully eval this, but discard its result.
+            scoped_eval(*definition, &vars);
+
+            // Actually use this part.
+            scoped_eval(*in_expr, vars)
+        },
+
         Func(name, args) => {
             let func_expr = match vars.get(&name) {
                 Some(resolved) => {
@@ -93,8 +101,8 @@ pub fn scoped_eval(expr: Expr, vars: &Scope) -> Evaluated {
             eval_apply(scoped_eval(*func_expr, vars), args, vars)
         },
 
-        Match(condition, branches) => {
-            eval_match(scoped_eval(*condition, vars), branches, vars)
+        Case(condition, branches) => {
+            eval_case(scoped_eval(*condition, vars), branches, vars)
         },
 
         Operator(left_arg, op, right_arg) => {
@@ -225,7 +233,7 @@ fn eval_operator(Evaluated(left_expr): &Evaluated, op: Operator, Evaluated(right
 }
 
 #[inline(always)]
-fn eval_match (condition: Evaluated, branches: SmallVec<[(Pattern, Box<Expr>); 4]>, vars: &Scope) -> Evaluated {
+fn eval_case (condition: Evaluated, branches: SmallVec<[(Pattern, Box<Expr>); 4]>, vars: &Scope) -> Evaluated {
     let Evaluated(ref evaluated_expr) = condition;
 
     for (pattern, definition) in branches {
@@ -254,6 +262,14 @@ fn pattern_match(evaluated: Evaluated, pattern: Pattern, vars: &mut Scope) -> Re
             // Underscore matches anything, and records no new vars.
             Ok(())
         },
+        Pattern::EmptyRecord => {
+            match evaluated {
+                Evaluated(Expr::EmptyRecord) => Ok(()),
+                Evaluated(expr) => Err(TypeMismatch(
+                    format!("Wanted a `{}`, but was given `{}`.", "{}", expr)
+                ))
+            }
+        },
         Variant(pattern_variant_name, opt_pattern_contents) => {
             match evaluated {
                 Evaluated(ApplyVariant(applied_variant_name, opt_applied_contents)) => {

src/expr.rs

@@ -23,9 +23,12 @@ pub enum Expr {
     // Sum Types
     ApplyVariant(String, Option<Vec<Expr>>),
 
+    // Product Types
+    EmptyRecord,
+
     // Conditionals
     If(Box<Expr>, Box<Expr>, Box<Expr>),
-    Match(Box<Expr>, SmallVec<[(Pattern, Box<Expr>); 4]>),
+    Case(Box<Expr>, SmallVec<[(Pattern, Box<Expr>); 4]>),
 
     // Error
     Error(Problem),
@@ -104,6 +107,7 @@ pub enum Problem {
 pub enum Pattern {
     Identifier(String),
     Variant(String, Option<Vec<Pattern>>),
+    EmptyRecord,
     Underscore
 }
 

src/parse.rs

@@ -123,7 +123,9 @@ parser! {
         let min_indent = *min_indent_ref;
 
         choice((
+            closure(min_indent),
             parenthetical_expr(min_indent),
+            string("{}").with(value(Expr::EmptyRecord)),
             string("True").with(value(Expr::Bool(true))),
             string("False").with(value(Expr::Bool(false))),
             string_literal(),
@@ -131,7 +133,6 @@ parser! {
             char_literal(),
             if_expr(min_indent),
             match_expr(min_indent),
-            closure(min_indent),
             let_expr(min_indent),
             apply_variant(min_indent),
             func_or_var(min_indent),
@@ -204,7 +205,7 @@ pub fn match_expr<I>(min_indent: i32) -> impl Parser<Input = I, Output = Expr>
 where I: Stream<Item = char, Position = IndentablePosition>,
     I::Error: ParseError<I::Item, I::Range, I::Position>
 {
-    string("match").skip(indented_whitespaces1(min_indent))
+    string("case").skip(indented_whitespaces1(min_indent))
         .with(expr_body(min_indent)).skip(indented_whitespaces1(min_indent))
         .and(
             many::<SmallVec<_>, _>(
@@ -219,7 +220,7 @@ where I: Stream<Item = char, Position = IndentablePosition>,
                 // TODO handle this more gracefully
                 panic!("encountered match-expression with no branches!")
             } else {
-                Expr::Match(Box::new(conditional), branches)
+                Expr::Case(Box::new(conditional), branches)
             }
         )
 }
@@ -336,15 +337,20 @@ where I: Stream<Item = char, Position = IndentablePosition>,
     I::Error: ParseError<I::Item, I::Range, I::Position>
 {
     // TODO patterns must be separated by commas!
-    between(char('|'), char('|'),
+    attempt(
+        between(char('('), char(')'),
             sep_by1(
                 pattern(min_indent),
                 char(',').skip(indented_whitespaces(min_indent))
             ))
-        .and(whitespace1().with(expr_body(min_indent)))
-        .map(|(patterns, closure_body)| {
-            Expr::Closure(patterns, Box::new(closure_body))
-        })
+        .skip(indented_whitespaces1(min_indent))
+        .skip(string("->"))
+        .skip(indented_whitespaces1(min_indent))
+    )
+    .and(expr_body(min_indent))
+    .map(|(patterns, closure_body)| {
+        Expr::Closure(patterns, Box::new(closure_body))
+    })
 }
 
 parser! {
@@ -356,6 +362,7 @@ parser! {
 
         choice((
             char('_').map(|_| Pattern::Underscore),
+            string("{}").map(|_| Pattern::EmptyRecord),
             ident().map(|name| Pattern::Identifier(name)),
             match_variant(min_indent)
         ))
@@ -420,7 +427,7 @@ where I: Stream<Item = char, Position = IndentablePosition>,
                     "if" => unexpected_any("Reserved keyword `if`").left(),
                     "then" => unexpected_any("Reserved keyword `then`").left(),
                     "else" => unexpected_any("Reserved keyword `else`").left(),
-                    "match" => unexpected_any("Reserved keyword `match`").left(),
+                    "case" => unexpected_any("Reserved keyword `case`").left(),
                     "when" => unexpected_any("Reserved keyword `when`").left(),
                     _ => value(ident_str).right()
                 }