WIP: Initial prototype of how to exclude code from Base

base/Makefile

@@ -67,6 +67,11 @@ endif
 	@echo "const DOCDIR = \"$(docdir_rel)\"" >> $@
 	@echo "const LIBDIR = \"$(libdir_rel)\"" >> $@
 	@echo "const INCLUDEDIR = \"$(includedir_rel)\"" >> $@
+ifeq ($(NODATES), 1)
+	@echo "const NODATES = true" >> $@
+else
+	@echo "const NODATES = false" >> $@
+endif
 
 	@# This to ensure that we always rebuild this file, but only when it is modified do we touch build_h.jl,
 	@# ensuring we rebuild the system image as infrequently as possible

base/excluded.jl

@@ -0,0 +1,22 @@
+# This file is a part of Julia. License is MIT: http://julialang.org/license
+
+module Excluded
+
+macro exclude(typexpr)
+    f = typexpr.args[2]
+    if typexpr.head == :type
+        return quote
+            export $f
+            type $f
+                $(f)() = throw(ArgumentError("`$($f)` has been excluded in this build"))
+            end
+        end
+    end
+end
+
+export Dates
+module Dates end
+@exclude type Date end
+@exclude type DateTime end
+
+end # module

base/sysimg.jl

@@ -78,6 +78,9 @@ Array{T}(::Type{T}, m::Integer)                       = Array{T,1}(Int(m))
 Array{T}(::Type{T}, m::Integer,n::Integer)            = Array{T,2}(Int(m),Int(n))
 Array{T}(::Type{T}, m::Integer,n::Integer,o::Integer) = Array{T,3}(Int(m),Int(n),Int(o))
 
+include("excluded.jl")
+using .Excluded
+
 # numeric operations
 include("hashing.jl")
 include("rounding.jl")
@@ -323,8 +326,10 @@ include("profile.jl")
 importall .Profile
 
 # dates
-include("Dates.jl")
-import .Dates: Date, DateTime, now
+if !NODATES
+    include("Dates.jl")
+    import .Dates: Date, DateTime, now
+end
 
 # sparse matrices, vectors, and sparse linear algebra
 include("sparse.jl")