Check repr attribute consistency at check time, not translation.

Note that raising an error during trans doesn't stop the compile or cause
rustc to exit with a failure status, currently, so this is of more than
cosmetic importance.

src/librustc/middle/trans/adt.rs

@@ -150,6 +150,8 @@ fn represent_type_uncached(cx: &mut CrateContext, t: ty::t) -> Repr {
 
             if cases.len() == 0 {
                 // Uninhabitable; represent as unit
+                // (Typechecking will reject discriminant-sizing attrs.)
+                assert_eq!(hint, attr::ReprAny);
                 return Univariant(mk_struct(cx, [], false), false);
             }
 
@@ -165,13 +167,6 @@ fn represent_type_uncached(cx: &mut CrateContext, t: ty::t) -> Repr {
                 return mk_cenum(cx, hint, &bounds);
             }
 
-            if cases.len() == 1 {
-                // Equivalent to a struct/tuple/newtype.
-                // FIXME: should this conflict with a discriminant size hint?
-                assert_eq!(cases[0].discr, 0);
-                return Univariant(mk_struct(cx, cases[0].tys, false), false)
-            }
-
             // Since there's at least one
             // non-empty body, explicit discriminants should have
             // been rejected by a checker before this point.
@@ -181,8 +176,15 @@ fn represent_type_uncached(cx: &mut CrateContext, t: ty::t) -> Repr {
                                  ty::item_path_str(cx.tcx, def_id)))
             }
 
-            if cases.len() == 2 {
-                // FIXME: disable if size hint present?
+            if cases.len() == 1 {
+                // Equivalent to a struct/tuple/newtype.
+                // (Typechecking will reject discriminant-sizing attrs.)
+                assert_eq!(hint, attr::ReprAny);
+                return Univariant(mk_struct(cx, cases[0].tys, false), false)
+            }
+
+            if cases.len() == 2 && hint == attr::ReprAny {
+                // Nullable pointer optimization
                 let mut discr = 0;
                 while discr < 2 {
                     if cases[1 - discr].is_zerolen(cx) {
@@ -205,7 +207,6 @@ fn represent_type_uncached(cx: &mut CrateContext, t: ty::t) -> Repr {
             }
 
             // The general case.
-            let hint = ty::lookup_repr_hint(cx.tcx, def_id);
             assert!((cases.len() - 1) as i64 >= 0);
             let bounds = IntBounds { ulo: 0, uhi: (cases.len() - 1) as u64,
                                      slo: 0, shi: (cases.len() - 1) as i64 };
@@ -307,7 +308,7 @@ fn range_to_inttype(cx: &mut CrateContext, hint: Hint, bounds: &IntBounds) -> In
     match hint {
         attr::ReprInt(span, ity) => {
             if !bounds_usable(cx, ity, bounds) {
-                cx.sess.span_err(span, "representation hint insufficient for discriminant range")
+                cx.sess.span_bug(span, "representation hint insufficient for discriminant range")
             }
             return ity;
         }
@@ -365,6 +366,7 @@ fn ty_of_inttype(ity: IntType) -> ty::t {
     }
 }
 
+
 /**
  * Returns the fields of a struct for the given representation.
  * All nominal types are LLVM structs, in order to be able to use

src/librustc/middle/typeck/check/mod.rs

@@ -121,6 +121,7 @@ use syntax::ast;
 use syntax::ast_map;
 use syntax::ast_util::local_def;
 use syntax::ast_util;
+use syntax::attr;
 use syntax::codemap::Span;
 use syntax::codemap;
 use syntax::opt_vec::OptVec;
@@ -3159,9 +3160,38 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
                            sp: Span,
                            vs: &[ast::variant],
                            id: ast::NodeId) {
+
+    fn disr_in_range(ccx: @mut CrateCtxt,
+                     ty: attr::IntType,
+                     disr: ty::Disr) -> bool {
+        fn uint_in_range(ccx: @mut CrateCtxt, ty: ast::uint_ty, disr: ty::Disr) -> bool {
+            match ty {
+                ast::ty_u8 => disr as u8 as Disr == disr,
+                ast::ty_u16 => disr as u16 as Disr == disr,
+                ast::ty_u32 => disr as u32 as Disr == disr,
+                ast::ty_u64 => disr as u64 as Disr == disr,
+                ast::ty_u => uint_in_range(ccx, ccx.tcx.sess.targ_cfg.uint_type, disr)
+            }
+        }
+        fn int_in_range(ccx: @mut CrateCtxt, ty: ast::int_ty, disr: ty::Disr) -> bool {
+            match ty {
+                ast::ty_i8 => disr as i8 as Disr == disr,
+                ast::ty_i16 => disr as i16 as Disr == disr,
+                ast::ty_i32 => disr as i32 as Disr == disr,
+                ast::ty_i64 => disr as i64 as Disr == disr,
+                ast::ty_i => int_in_range(ccx, ccx.tcx.sess.targ_cfg.int_type, disr)
+            }
+        }
+        match ty {
+            attr::UnsignedInt(ty) => uint_in_range(ccx, ty, disr),
+            attr::SignedInt(ty) => int_in_range(ccx, ty, disr)
+        }
+    }
+
     fn do_check(ccx: @mut CrateCtxt,
                 vs: &[ast::variant],
-                id: ast::NodeId)
+                id: ast::NodeId,
+                hint: attr::ReprAttr)
                 -> ~[@ty::VariantInfo] {
 
         let rty = ty::node_id_to_type(ccx.tcx, id);
@@ -3203,9 +3233,20 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
                 None => ()
             };
 
-            // Check for duplicate discriminator values
+            // Check for duplicate discriminant values
             if disr_vals.contains(&current_disr_val) {
-                ccx.tcx.sess.span_err(v.span, "discriminator value already exists");
+                ccx.tcx.sess.span_err(v.span, "discriminant value already exists");
+            }
+            // Check for unrepresentable discriminant values
+            match hint {
+                attr::ReprAny | attr::ReprExtern => (),
+                attr::ReprInt(sp, ity) => {
+                    if !disr_in_range(ccx, ity, current_disr_val) {
+                        ccx.tcx.sess.span_err(v.span,
+                                              "discriminant value outside specified type");
+                        ccx.tcx.sess.span_note(sp, "discriminant type specified here");
+                    }
+                }
             }
             disr_vals.push(current_disr_val);
 
@@ -3219,8 +3260,13 @@ pub fn check_enum_variants(ccx: @mut CrateCtxt,
     }
 
     let rty = ty::node_id_to_type(ccx.tcx, id);
+    let hint = ty::lookup_repr_hint(ccx.tcx, ast::DefId { crate: ast::LOCAL_CRATE, node: id });
+    if hint != attr::ReprAny && vs.len() <= 1 {
+        ccx.tcx.sess.span_err(sp, format!("unsupported representation for {}variant enum",
+                                          if vs.len() == 1 { "uni" } else { "zero-" }))
+    }
 
-    let variants = do_check(ccx, vs, id);
+    let variants = do_check(ccx, vs, id, hint);
 
     // cache so that ty::enum_variants won't repeat this work
     ccx.tcx.enum_var_cache.insert(local_def(id), @variants);

src/test/compile-fail/tag-variant-disr-dup.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//error-pattern:discriminator value already exists
+//error-pattern:discriminant value already exists
 
 // black and white have the same discriminator value ...