librustc: Implement `|A| -> B` syntax for closures and make bare `fn`

work

10 files changed, 320 insertions, 57 deletions

diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index 2f8c1f6f97d..ab1ca420afa 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -308,10 +308,11 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
                       ident: Option<ast::Ident>,
                       sig: &ty::FnSig)
                       -> ~str {
-        let mut s = ~"extern ";
-
-        s.push_str(abis.to_str());
-        s.push_char(' ');
+        let mut s = if abis.is_rust() {
+            ~""
+        } else {
+            format!("extern {} ", abis.to_str())
+        };
 
         match purity {
             ast::impure_fn => {}
@@ -331,16 +332,16 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
           _ => { }
         }
 
-        push_sig_to_str(cx, &mut s, sig);
+        push_sig_to_str(cx, &mut s, '(', ')', sig);
 
         return s;
     }
-    fn closure_to_str(cx: ctxt, cty: &ty::ClosureTy) -> ~str
-    {
+    fn closure_to_str(cx: ctxt, cty: &ty::ClosureTy) -> ~str {
         let is_proc =
             (cty.sigil, cty.onceness) == (ast::OwnedSigil, ast::Once);
+        let is_borrowed_closure = cty.sigil == ast::BorrowedSigil;
 
-        let mut s = if is_proc {
+        let mut s = if is_proc || is_borrowed_closure {
             ~""
         } else {
             cty.sigil.to_str()
@@ -374,23 +375,42 @@ pub fn ty_to_str(cx: ctxt, typ: t) -> ~str {
                 }
             };
 
-            s.push_str("fn");
+            if !is_borrowed_closure {
+                s.push_str("fn");
+            }
         }
 
-        if !cty.bounds.is_empty() {
-            s.push_str(":");
-        }
-        s.push_str(cty.bounds.repr(cx));
+        if !is_borrowed_closure {
+            // Print bounds before `fn` if this is not a borrowed closure.
+            if !cty.bounds.is_empty() {
+                s.push_str(":");
+                s.push_str(cty.bounds.repr(cx));
+            }
+
+            push_sig_to_str(cx, &mut s, '(', ')', &cty.sig);
+        } else {
+            // Print bounds after the signature if this is a borrowed closure.
+            push_sig_to_str(cx, &mut s, '|', '|', &cty.sig);
 
-        push_sig_to_str(cx, &mut s, &cty.sig);
+            if is_borrowed_closure {
+                if !cty.bounds.is_empty() {
+                    s.push_str(":");
+                    s.push_str(cty.bounds.repr(cx));
+                }
+            }
+        }
 
         return s;
     }
-    fn push_sig_to_str(cx: ctxt, s: &mut ~str, sig: &ty::FnSig) {
-        s.push_char('(');
+    fn push_sig_to_str(cx: ctxt,
+                       s: &mut ~str,
+                       bra: char,
+                       ket: char,
+                       sig: &ty::FnSig) {
+        s.push_char(bra);
         let strs = sig.inputs.map(|a| fn_input_to_str(cx, *a));
         s.push_str(strs.connect(", "));
-        s.push_char(')');
+        s.push_char(ket);
         if ty::get(sig.output).sty != ty_nil {
             s.push_str(" -> ");
             if ty::type_is_bot(sig.output) {
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 68796a39f1b..56254704e28 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -561,6 +561,45 @@ impl Parser {
         }
     }
 
+    // Expect and consume a `|`. If `||` is seen, replace it with a single
+    // `|` and continue. If a `|` is not seen, signal an error.
+    fn expect_or(&self) {
+        match *self.token {
+            token::BINOP(token::OR) => self.bump(),
+            token::OROR => {
+                self.replace_token(token::BINOP(token::OR),
+                                   self.span.lo + BytePos(1),
+                                   self.span.hi)
+            }
+            _ => {
+                let found_token = self.token_to_str(&token::BINOP(token::OR));
+                self.fatal(format!("expected `{}`, found `{}`",
+                                   found_token,
+                                   self.this_token_to_str()))
+            }
+        }
+    }
+
+    // Parse a sequence bracketed by `|` and `|`, stopping before the `|`.
+    fn parse_seq_to_before_or<T>(&self,
+                                 sep: &token::Token,
+                                 f: &fn(&Parser) -> T)
+                                 -> ~[T] {
+        let mut first = true;
+        let mut vector = ~[];
+        while *self.token != token::BINOP(token::OR) &&
+                *self.token != token::OROR {
+            if first {
+                first = false
+            } else {
+                self.expect(sep)
+            }
+
+            vector.push(f(self))
+        }
+        vector
+    }
+
     // expect and consume a GT. if a >> is seen, replace it
     // with a single > and continue. If a GT is not seen,
     // signal an error.
@@ -761,11 +800,33 @@ impl Parser {
         get_ident_interner().get(id.name)
     }
 
-    // is this one of the keywords that signals a closure type?
-    pub fn token_is_closure_keyword(&self, tok: &token::Token) -> bool {
-        token::is_keyword(keywords::Unsafe, tok) ||
-            token::is_keyword(keywords::Once, tok) ||
-            token::is_keyword(keywords::Fn, tok)
+    // Is the current token one of the keywords that signals a bare function
+    // type?
+    pub fn token_is_bare_fn_keyword(&self) -> bool {
+        if token::is_keyword(keywords::Fn, self.token) {
+            return true
+        }
+
+        if token::is_keyword(keywords::Unsafe, self.token) ||
+            token::is_keyword(keywords::Once, self.token) {
+            return self.look_ahead(1, |t| token::is_keyword(keywords::Fn, t))
+        }
+
+        false
+    }
+
+    // Is the current token one of the keywords that signals a closure type?
+    pub fn token_is_closure_keyword(&self) -> bool {
+        token::is_keyword(keywords::Unsafe, self.token) ||
+            token::is_keyword(keywords::Once, self.token)
+    }
+
+    // Is the current token one of the keywords that signals an old-style
+    // closure type (with explicit sigil)?
+    pub fn token_is_old_style_closure_keyword(&self) -> bool {
+        token::is_keyword(keywords::Unsafe, self.token) ||
+            token::is_keyword(keywords::Once, self.token) ||
+            token::is_keyword(keywords::Fn, self.token)
     }
 
     pub fn token_is_lifetime(&self, tok: &token::Token) -> bool {
@@ -786,15 +847,15 @@ impl Parser {
     pub fn parse_ty_bare_fn(&self) -> ty_ {
         /*
 
-        extern "ABI" [unsafe] fn <'lt> (S) -> T
-               ^~~~^ ^~~~~~~^    ^~~~^ ^~^    ^
-                 |     |           |    |     |
-                 |     |           |    |   Return type
-                 |     |           |  Argument types
-                 |     |       Lifetimes
-                 |     |
-                 |   Purity
-                ABI
+        [extern "ABI"] [unsafe] fn <'lt> (S) -> T
+                ^~~~^  ^~~~~~~^    ^~~~^ ^~^    ^
+                  |      |           |    |     |
+                  |      |           |    |   Return type
+                  |      |           |  Argument types
+                  |      |       Lifetimes
+                  |      |
+                  |    Purity
+                 ABI
 
         */
 
@@ -828,8 +889,8 @@ impl Parser {
 
     // parse a ty_closure type
     pub fn parse_ty_closure(&self,
-                            sigil: ast::Sigil,
-                            region: Option<ast::Lifetime>)
+                            opt_sigil: Option<ast::Sigil>,
+                            mut region: Option<ast::Lifetime>)
                             -> ty_ {
         /*
 
@@ -852,10 +913,58 @@ impl Parser {
 
         let purity = self.parse_unsafety();
         let onceness = parse_onceness(self);
-        self.expect_keyword(keywords::Fn);
-        let bounds = self.parse_optional_ty_param_bounds();
 
-        let (decl, lifetimes) = self.parse_ty_fn_decl();
+        let (sigil, decl, lifetimes, bounds) = match opt_sigil {
+            Some(sigil) => {
+                // Old-style closure syntax (`fn(A)->B`).
+                self.expect_keyword(keywords::Fn);
+                let bounds = self.parse_optional_ty_param_bounds();
+                let (decl, lifetimes) = self.parse_ty_fn_decl();
+                (sigil, decl, lifetimes, bounds)
+            }
+            None => {
+                // New-style closure syntax (`<'lt>|A|:K -> B`).
+                let lifetimes = if self.eat(&token::LT) {
+                    let lifetimes = self.parse_lifetimes();
+                    self.expect_gt();
+
+                    // Re-parse the region here. What a hack.
+                    if region.is_some() {
+                        self.span_err(*self.last_span,
+                                      "lifetime declarations must precede \
+                                       the lifetime associated with a \
+                                       closure");
+                    }
+                    region = self.parse_opt_lifetime();
+
+                    lifetimes
+                } else {
+                    opt_vec::Empty
+                };
+
+                let inputs = if self.eat(&token::OROR) {
+                    ~[]
+                } else {
+                    self.expect_or();
+                    let inputs = self.parse_seq_to_before_or(
+                        &token::COMMA,
+                        |p| p.parse_arg_general(false));
+                    self.expect_or();
+                    inputs
+                };
+
+                let bounds = self.parse_optional_ty_param_bounds();
+
+                let (return_style, output) = self.parse_ret_ty();
+                let decl = ast::fn_decl {
+                    inputs: inputs,
+                    output: output,
+                    cf: return_style,
+                };
+
+                (BorrowedSigil, decl, lifetimes, bounds)
+            }
+        };
 
         return ty_closure(@TyClosure {
             sigil: sigil,
@@ -1120,13 +1229,23 @@ impl Parser {
             // BORROWED POINTER
             self.bump();
             self.parse_borrowed_pointee()
-        } else if self.eat_keyword(keywords::Extern) {
-            // EXTERN FUNCTION
+        } else if self.is_keyword(keywords::Extern) ||
+                self.token_is_bare_fn_keyword() {
+            // BARE FUNCTION
             self.parse_ty_bare_fn()
-        } else if self.token_is_closure_keyword(self.token) {
+        } else if self.token_is_closure_keyword() ||
+                *self.token == token::BINOP(token::OR) ||
+                *self.token == token::OROR ||
+                *self.token == token::LT ||
+                self.token_is_lifetime(self.token) {
             // CLOSURE
-            let result = self.parse_ty_closure(ast::BorrowedSigil, None);
-            self.obsolete(*self.last_span, ObsoleteBareFnType);
+            //
+            // XXX(pcwalton): Eventually `token::LT` will not unambiguously
+            // introduce a closure, once procs can have lifetime bounds. We
+            // will need to refactor the grammar a little bit at that point.
+
+            let lifetime = self.parse_opt_lifetime();
+            let result = self.parse_ty_closure(None, lifetime);
             result
         } else if self.eat_keyword(keywords::Typeof) {
             // TYPEOF
@@ -1161,12 +1280,12 @@ impl Parser {
         match *self.token {
             token::LIFETIME(*) => {
                 let lifetime = self.parse_lifetime();
-                return self.parse_ty_closure(sigil, Some(lifetime));
+                return self.parse_ty_closure(Some(sigil), Some(lifetime));
             }
 
             token::IDENT(*) => {
-                if self.token_is_closure_keyword(self.token) {
-                    return self.parse_ty_closure(sigil, None);
+                if self.token_is_old_style_closure_keyword() {
+                    return self.parse_ty_closure(Some(sigil), None);
                 }
             }
             _ => {}
@@ -1187,8 +1306,8 @@ impl Parser {
         // look for `&'lt` or `&'foo ` and interpret `foo` as the region name:
         let opt_lifetime = self.parse_opt_lifetime();
 
-        if self.token_is_closure_keyword(self.token) {
-            return self.parse_ty_closure(BorrowedSigil, opt_lifetime);
+        if self.token_is_old_style_closure_keyword() {
+            return self.parse_ty_closure(Some(BorrowedSigil), opt_lifetime);
         }
 
         let mt = self.parse_mt();
@@ -4390,8 +4509,13 @@ impl Parser {
         }
     }
 
-    // parse a string as an ABI spec on an extern type or module
+    // Parses a string as an ABI spec on an extern type or module. Consumes
+    // the `extern` keyword, if one is found.
     fn parse_opt_abis(&self) -> Option<AbiSet> {
+        if !self.eat_keyword(keywords::Extern) {
+            return None
+        }
+
         match *self.token {
             token::LIT_STR(s)
             | token::LIT_STR_RAW(s, _) => {
@@ -4467,7 +4591,7 @@ impl Parser {
             });
         }
         // either a view item or an item:
-        if self.eat_keyword(keywords::Extern) {
+        if self.is_keyword(keywords::Extern) {
             let opt_abis = self.parse_opt_abis();
 
             if self.eat_keyword(keywords::Fn) {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 33bdcdd1b03..0eb1045efe9 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -2015,20 +2015,39 @@ pub fn print_ty_fn(s: @ps,
     // function prints the sigil in the wrong place.  That should be fixed.
     if opt_sigil == Some(ast::OwnedSigil) && onceness == ast::Once {
         word(s.s, "proc");
-    } else {
+    } else if opt_sigil == Some(ast::BorrowedSigil) {
         print_extern_opt_abis(s, opt_abis);
+        for lifetime in opt_region.iter() {
+            print_lifetime(s, lifetime);
+        }
+        print_purity(s, purity);
+        print_onceness(s, onceness);
+    } else {
+        print_opt_abis_and_extern_if_nondefault(s, opt_abis);
         print_opt_sigil(s, opt_sigil);
         print_opt_lifetime(s, opt_region);
         print_purity(s, purity);
         print_onceness(s, onceness);
         word(s.s, "fn");
     }
+
     match id { Some(id) => { word(s.s, " "); print_ident(s, id); } _ => () }
-    do opt_bounds.as_ref().map |bounds| { print_bounds(s, bounds, true); };
+
+    if opt_sigil != Some(ast::BorrowedSigil) {
+        do opt_bounds.as_ref().map |bounds| {
+            print_bounds(s, bounds, true);
+        };
+    }
+
     match generics { Some(g) => print_generics(s, g), _ => () }
     zerobreak(s.s);
 
-    popen(s);
+    if opt_sigil == Some(ast::BorrowedSigil) {
+        word(s.s, "|");
+    } else {
+        popen(s);
+    }
+
     // It is unfortunate to duplicate the commasep logic, but we want the
     // self type and the args all in the same box.
     box(s, 0u, inconsistent);
@@ -2041,7 +2060,14 @@ pub fn print_ty_fn(s: @ps,
         print_arg(s, arg);
     }
     end(s);
-    pclose(s);
+
+    if opt_sigil == Some(ast::BorrowedSigil) {
+        word(s.s, "|");
+
+        opt_bounds.as_ref().map(|bounds| print_bounds(s, bounds, true));
+    } else {
+        pclose(s);
+    }
 
     maybe_print_comment(s, decl.output.span.lo);
 
@@ -2274,6 +2300,17 @@ pub fn print_opt_purity(s: @ps, opt_purity: Option<ast::purity>) {
     }
 }
 
+pub fn print_opt_abis_and_extern_if_nondefault(s: @ps,
+                                               opt_abis: Option<AbiSet>) {
+    match opt_abis {
+        Some(abis) if !abis.is_rust() => {
+            word_nbsp(s, "extern");
+            word_nbsp(s, abis.to_str());
+        }
+        Some(_) | None => {}
+    };
+}
+
 pub fn print_extern_opt_abis(s: @ps, opt_abis: Option<AbiSet>) {
     match opt_abis {
         Some(abis) => {
diff --git a/src/test/compile-fail/block-coerce-no-2.rs b/src/test/compile-fail/block-coerce-no-2.rs
index 85ef09cc2a6..3e38ce9ab35 100644
--- a/src/test/compile-fail/block-coerce-no-2.rs
+++ b/src/test/compile-fail/block-coerce-no-2.rs
@@ -19,5 +19,5 @@ fn main() {
     }
 
     f(g);
-    //~^ ERROR mismatched types: expected `extern "Rust" fn(extern "Rust" fn(extern "Rust" fn()))`
+    //~^ ERROR mismatched types: expected `fn(fn(fn()))`
 }
diff --git a/src/test/compile-fail/closure-reform-bad.rs b/src/test/compile-fail/closure-reform-bad.rs
new file mode 100644
index 00000000000..3da709942e0
--- /dev/null
+++ b/src/test/compile-fail/closure-reform-bad.rs
@@ -0,0 +1,13 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+fn call_bare(f: fn(&str)) {
+    f("Hello ");
+}
+
+fn main() {
+    let string = "world!";
+    let f: |&str| = |s| println(s + string);
+    call_bare(f)    //~ ERROR mismatched types
+}
+
diff --git a/src/test/pretty/closure-reform-pretty.rs b/src/test/pretty/closure-reform-pretty.rs
new file mode 100644
index 00000000000..5169652a6c0
--- /dev/null
+++ b/src/test/pretty/closure-reform-pretty.rs
@@ -0,0 +1,17 @@
+// Any copyright is dedicated to the Public Domain.
+// http://creativecommons.org/publicdomain/zero/1.0/
+
+// pp-exact
+
+fn call_it(f: proc(~str) -> ~str) { }
+
+fn call_this(f: |&str|: Send) { }
+
+fn call_that(f: <'a>|&'a int, &'a int|: -> int) { }
+
+fn call_extern(f: fn() -> int) { }
+
+fn call_abid_extern(f: extern "C" fn() -> int) { }
+
+pub fn main() { }
+
diff --git a/src/test/pretty/disamb-stmt-expr.rs b/src/test/pretty/disamb-stmt-expr.rs
index f6787fa9c3d..d3d6f1c0e35 100644
--- a/src/test/pretty/disamb-stmt-expr.rs
+++ b/src/test/pretty/disamb-stmt-expr.rs
@@ -14,7 +14,7 @@
 // preserved.  They are needed to disambiguate `{return n+1}; - 0` from
 // `({return n+1}-0)`.
 
-fn id(f: &fn() -> int) -> int { f() }
+fn id(f: || -> int) -> int { f() }
 
 fn wsucc(_n: int) -> int { (do id || { 1 }) - 0 }
 fn main() { }
diff --git a/src/test/pretty/do1.rs b/src/test/pretty/do1.rs
index 751aedb39a3..1fb2359da53 100644
--- a/src/test/pretty/do1.rs
+++ b/src/test/pretty/do1.rs
@@ -10,6 +10,6 @@
 
 // pp-exact
 
-fn f(f: &fn(int)) { f(10) }
+fn f(f: |int|) { f(10) }
 
 fn main() { do f |i| { assert!(i == 10) } }
diff --git a/src/test/pretty/fn-types.rs b/src/test/pretty/fn-types.rs
index b000c9f9137..27e56fb6074 100644
--- a/src/test/pretty/fn-types.rs
+++ b/src/test/pretty/fn-types.rs
@@ -10,7 +10,7 @@
 
 // pp-exact
 
-fn from_foreign_fn(_x: extern "Rust" fn()) { }
-fn from_stack_closure(_x: &fn()) { }
+fn from_foreign_fn(_x: fn()) { }
+fn from_stack_closure(_x: ||) { }
 fn from_unique_closure(_x: ~fn()) { }
 fn main() { }
diff --git a/src/test/run-pass/closure-reform.rs b/src/test/run-pass/closure-reform.rs
index c765ebe9643..18ca64d0f27 100644
--- a/src/test/run-pass/closure-reform.rs
+++ b/src/test/run-pass/closure-reform.rs
@@ -1,11 +1,42 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
+use std::cast;
+
 fn call_it(f: proc(~str) -> ~str) {
     println(f(~"Fred"))
 }
 
+fn call_a_thunk(f: ||) {
+    f();
+}
+
+fn call_this(f: |&str|:Send) {
+    f("Hello!");
+}
+
+fn call_that(f: <'a>|&'a int, &'a int|: -> int) {
+    let (ten, forty_two) = (10, 42);
+    println!("Your lucky number is {}", f(&ten, &forty_two));
+}
+
+fn call_cramped(f:||->uint,g:<'a>||->&'a uint) {
+    let number = f();
+    let other_number = *g();
+    println!("Ticket {} wins an all-expenses-paid trip to Mountain View", number + other_number);
+}
+
+fn call_bare(f: fn(&str)) {
+    f("Hello world!")
+}
+
+fn call_bare_again(f: extern "Rust" fn(&str)) {
+    f("Goodbye world!")
+}
+
 pub fn main() {
+    // Procs
+
     let greeting = ~"Hi ";
     do call_it |s| {
         greeting + s
@@ -23,5 +54,26 @@ pub fn main() {
     call_it(proc(s: ~str) -> ~str {
         greeting + s
     });
+
+    // Closures
+
+    call_a_thunk(|| println("Hello world!"));
+
+    call_this(|s| println(s));
+
+    call_that(|x, y| *x + *y);
+
+    let z = 100;
+    call_that(|x, y| *x + *y - z);
+
+    call_cramped(|| 1, || unsafe {
+        cast::transmute(&100)
+    });
+
+    // External functions
+
+    call_bare(println);
+
+    call_bare_again(println);
 }