Merge pull request #4459 from jld/constenum

Allow consts to be initialized by non-nullary enum constructors

Author: catamorphism

src/librustc/middle/check_const.rs

@@ -138,11 +138,12 @@ fn check_expr(sess: Session, def_map: resolve::DefMap,
           expr_call(callee, _, false) => {
             match def_map.find(callee.id) {
                 Some(def_struct(*)) => {}    // OK.
+                Some(def_variant(*)) => {}    // OK.
                 _ => {
                     sess.span_err(
                         e.span,
                         ~"function calls in constants are limited to \
-                          structure constructors");
+                          struct and enum constructors");
                 }
             }
           }

src/librustc/middle/trans/base.rs

@@ -779,6 +779,30 @@ fn trans_external_path(ccx: @crate_ctxt, did: ast::def_id, t: ty::t)
     };
 }
 
+fn get_discrim_val(cx: @crate_ctxt, span: span, enum_did: ast::def_id,
+                   variant_did: ast::def_id) -> ValueRef {
+    // Can't use `discrims` from the crate context here because
+    // those discriminants have an extra level of indirection,
+    // and there's no LLVM constant load instruction.
+    let mut lldiscrim_opt = None;
+    for ty::enum_variants(cx.tcx, enum_did).each |variant_info| {
+        if variant_info.id == variant_did {
+            lldiscrim_opt = Some(C_int(cx,
+                                       variant_info.disr_val));
+            break;
+        }
+    }
+
+    match lldiscrim_opt {
+        None => {
+            cx.tcx.sess.span_bug(span, ~"didn't find discriminant?!");
+        }
+        Some(found_lldiscrim) => {
+            found_lldiscrim
+        }
+    }
+}
+
 fn lookup_discriminant(ccx: @crate_ctxt, vid: ast::def_id) -> ValueRef {
     unsafe {
         let _icx = ccx.insn_ctxt("lookup_discriminant");
@@ -2284,16 +2308,21 @@ fn get_item_val(ccx: @crate_ctxt, id: ast::node_id) -> ValueRef {
             let my_path = vec::append(/*bad*/copy *pth,
                                       ~[path_name(i.ident)]);
             match i.node {
-              ast::item_const(_, _) => {
+              ast::item_const(_, expr) => {
                 let typ = ty::node_id_to_type(ccx.tcx, i.id);
                 let s = mangle_exported_name(ccx, my_path, typ);
-                let g = str::as_c_str(s, |buf| {
-                    unsafe {
-                        llvm::LLVMAddGlobal(ccx.llmod, type_of(ccx, typ), buf)
-                    }
-                });
-                ccx.item_symbols.insert(i.id, s);
-                g
+                // We need the translated value here, because for enums the
+                // LLVM type is not fully determined by the Rust type.
+                let v = consts::const_expr(ccx, expr);
+                ccx.const_values.insert(id, v);
+                unsafe {
+                    let llty = llvm::LLVMTypeOf(v);
+                    let g = str::as_c_str(s, |buf| {
+                        llvm::LLVMAddGlobal(ccx.llmod, llty, buf)
+                    });
+                    ccx.item_symbols.insert(i.id, s);
+                    g
+                }
               }
               ast::item_fn(_, purity, _, _) => {
                 let llfn = if purity != ast::extern_fn {

src/librustc/middle/trans/consts.rs

@@ -414,42 +414,10 @@ fn const_expr(cx: @crate_ctxt, e: @ast::expr) -> ValueRef {
                     // variant or we wouldn't have gotten here -- the constant
                     // checker forbids paths that don't map to C-like enum
                     // variants.
-                    let ety = ty::expr_ty(cx.tcx, e);
-                    let llty = type_of::type_of(cx, ety);
-
-                    // Can't use `discrims` from the crate context here
-                    // because those discriminants have an extra level of
-                    // indirection, and there's no LLVM constant load
-                    // instruction.
-                    let mut lldiscrim_opt = None;
-                    for ty::enum_variants(cx.tcx, enum_did).each
-                            |variant_info| {
-                        if variant_info.id == variant_did {
-                            lldiscrim_opt = Some(C_int(cx,
-                                variant_info.disr_val));
-                            break;
-                        }
-                    }
-
-                    let lldiscrim;
-                    match lldiscrim_opt {
-                        None => {
-                            cx.tcx.sess.span_bug(e.span,
-                                ~"didn't find discriminant?!");
-                        }
-                        Some(found_lldiscrim) => {
-                            lldiscrim = found_lldiscrim;
-                        }
-                    }
-                    let fields = if ty::enum_is_univariant(cx.tcx, enum_did) {
-                        ~[lldiscrim]
-                    } else {
-                        let llstructtys =
-                            lib::llvm::struct_element_types(llty);
-                        ~[lldiscrim, C_null(llstructtys[1])]
-                    };
-
-                    C_named_struct(llty, fields)
+                    let lldiscrim = base::get_discrim_val(cx, e.span,
+                                                          enum_did,
+                                                          variant_did);
+                    C_struct(~[lldiscrim])
                 }
                 Some(ast::def_struct(_)) => {
                     let ety = ty::expr_ty(cx.tcx, e);
@@ -475,6 +443,24 @@ fn const_expr(cx: @crate_ctxt, e: @ast::expr) -> ValueRef {
                         C_named_struct(llty, ~[ llstructbody ])
                     }
                 }
+            Some(ast::def_variant(tid, vid)) => {
+                let ety = ty::expr_ty(cx.tcx, e);
+                let degen = ty::enum_is_univariant(cx.tcx, tid);
+                let size = shape::static_size_of_enum(cx, ety);
+
+                let discrim = base::get_discrim_val(cx, e.span, tid, vid);
+                let c_args = C_struct(args.map(|a| const_expr(cx, *a)));
+
+                let fields = if !degen {
+                    ~[discrim, c_args]
+                } else if size == 0 {
+                    ~[discrim]
+                } else {
+                    ~[c_args]
+                };
+
+                C_struct(fields)
+            }
                 _ => cx.sess.span_bug(e.span, ~"expected a struct def")
             }
           }
@@ -485,12 +471,13 @@ fn const_expr(cx: @crate_ctxt, e: @ast::expr) -> ValueRef {
     }
 }
 
-fn trans_const(ccx: @crate_ctxt, e: @ast::expr, id: ast::node_id) {
+fn trans_const(ccx: @crate_ctxt, _e: @ast::expr, id: ast::node_id) {
     unsafe {
         let _icx = ccx.insn_ctxt("trans_const");
         let g = base::get_item_val(ccx, id);
-        let v = const_expr(ccx, e);
-        ccx.const_values.insert(id, v);
+        // At this point, get_item_val has already translated the
+        // constant's initializer to determine its LLVM type.
+        let v = ccx.const_values.get(id);
         llvm::LLVMSetInitializer(g, v);
         llvm::LLVMSetGlobalConstant(g, True);
     }

src/librustc/middle/trans/expr.rs

@@ -801,7 +801,11 @@ fn trans_def_lvalue(bcx: block,
         ast::def_const(did) => {
             let const_ty = expr_ty(bcx, ref_expr);
             let val = if did.crate == ast::local_crate {
-                base::get_item_val(ccx, did.node)
+                // The LLVM global has the type of its initializer,
+                // which may not be equal to the enum's type for
+                // non-C-like enums.
+                PointerCast(bcx, base::get_item_val(ccx, did.node),
+                            T_ptr(type_of(bcx.ccx(), const_ty)))
             } else {
                 base::trans_external_path(ccx, did, const_ty)
             };

src/test/run-pass/const-big-enum.rs

@@ -0,0 +1,38 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum Foo {
+    Bar(u32),
+    Baz,
+    Quux(u64, u16)
+}
+
+const X: Foo = Baz;
+
+fn main() {
+    match X {
+        Baz => {}
+        _ => fail
+    }
+    match Y {
+        Bar(s) => assert(s == 2654435769),
+        _ => fail
+    }
+    match Z {
+        Quux(d,h) => {
+            assert(d == 0x123456789abcdef0);
+            assert(h == 0x1234);
+        }
+        _ => fail
+    }
+}
+
+const Y: Foo = Bar(2654435769);
+const Z: Foo = Quux(0x123456789abcdef0, 0x1234);

src/test/run-pass/const-enum-byref-self.rs

@@ -0,0 +1,25 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum E { V, VV(int) }
+const C: E = V;
+
+impl E {
+    fn method(&self) {
+        match *self {
+            V => {}
+            VV(*) => fail
+        }
+    }
+}
+
+fn main() {
+    C.method()
+}

src/test/run-pass/const-enum-byref.rs

@@ -0,0 +1,23 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum E { V, VV(int) }
+const C: E = V;
+
+fn f(a: &E) {
+    match *a {
+        V => {}
+        VV(*) => fail
+    }
+}
+
+fn main() {
+    f(&C)
+}

src/test/run-pass/const-newtype-enum.rs

@@ -0,0 +1,20 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+enum Foo = u32;
+
+const X: Foo = Foo(17);
+
+fn main() {
+    assert(*X == 17);
+    assert(*Y == 23);
+}
+
+const Y: Foo = Foo(23);

src/test/run-pass/const-nullary-enum.rs

@@ -1,4 +1,4 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -21,5 +21,10 @@ fn main() {
         Bar => {}
         Baz | Boo => fail
     }
+    match Y {
+        Baz => {}
+        Bar | Boo => fail
+    }
 }
 
+const Y: Foo = Baz;

src/test/run-pass/const-nullary-univariant-enum.rs

@@ -16,4 +16,7 @@ const X: Foo = Bar;
 
 fn main() {
     assert((X as uint) == 0xDEADBEE);
+    assert((Y as uint) == 0xDEADBEE);
 }
+
+const Y: Foo = Bar;