diff -r e3c851a14f16 -r 18f3010a358c src/compiler/SemanticAnalysis.cpp
--- a/src/compiler/SemanticAnalysis.cpp	Tue Dec 25 18:13:02 2012 -0800
+++ b/src/compiler/SemanticAnalysis.cpp	Wed Dec 26 17:14:12 2012 -0800
@@ -731,6 +731,11 @@
     if (!lval)
         return;
 
+    if (lval->type()->quals() & TypeQual_Const) {
+        cc_.reportError(node->pos(), Message_CannotModifyConst);
+        return;
+    }
+
     HIR *hir = eval(node->expression());
     if ((hir = coerce(hir, lval->type(), Coerce_Assign)) == NULL)
         return;
@@ -838,7 +843,7 @@
 HIR *
 SemanticAnalysis::typeCheckArray(const SourcePosition &pos,
                                  HIR *from,
-                                 Handle<Type> argActual,
+                                 Handle<ArrayType> argActual,
                                  CoercionKind kind)
 {
     Local<Type> argGiven(zone_, from->type());
@@ -888,7 +893,7 @@
         // We treat declaration separately from assignment, since for
         // declaration we can just immediately use the cloned version.
         bool shouldDuplicate = true;
-        if (0 /*actual->isConst() :TODO */ ||
+        if ((actual->quals() & TypeQual_Const) ||
             (actual->isFixedLength() && kind == Coerce_Assign))
         {
             shouldDuplicate = false;
@@ -959,11 +964,18 @@
         actual = ArrayType::cast(actual->contained());
     }
 
+    bool givenConst = !!(given->contained()->quals() & TypeQual_Const);
+    bool actualConst = !!(actual->contained()->quals() & TypeQual_Const);
+
     // These arrays must contain the same innermost type.
-    if (given->contained() != actual->contained()) {
+    if (given->contained()->unqualified() != actual->contained()->unqualified() ||
+        (givenConst && !actualConst))
+    {
+        char aname[255];
+        char gname[255];
         cc_.reportError(pos, Message_TypeMismatch,
-                        GetTypeName(actual->contained()),
-                        GetTypeName(given->contained()));
+                        GetTypeName(argActual, aname, sizeof(aname)),
+                        GetTypeName(argGiven, gname, sizeof(gname)));
         return false;
     }
 
@@ -973,9 +985,11 @@
 HIR *
 SemanticAnalysis::typeFailure(const SourcePosition &pos, Handle<Type> from, Handle<Type> to)
 {
+    char fname[255];
+    char tname[255];
     cc_.reportError(pos, Message_InvalidCoercion,
-                    GetTypeName(from),
-                    GetTypeName(to));
+                    GetTypeName(from, fname, sizeof(fname)),
+                    GetTypeName(to, tname, sizeof(tname)));
     return NULL;
 }
 
@@ -992,8 +1006,10 @@
     if (to->isEnum() && *from != to)
         return typeFailure(hir->node()->pos(), from, to);
     
-    if (to->isArray())
-        return typeCheckArray(SourcePosition(), hir, to, kind);
+    if (to->isArray()) {
+        Local<ArrayType> atype(zone_, ArrayType::cast(to));
+        return typeCheckArray(hir->node()->pos(), hir, atype, kind);
+    }
     
     return hir;
 }