Add new AssertionError Exception type

 * assert() and @Assert throw a more specific AssertionError type

 * the assertion error type has a field for the assertion expr and optional
   message

 * rework the assert macro to special case passing in booleans as the
   asserted expression

base/base.jl

@@ -118,6 +118,15 @@ type DimensionMismatch <: Exception
 end
 DimensionMismatch() = DimensionMismatch("")
 
+type AssertionError <: Exception
+    expr::Any
+    msg::AbstractString
+
+    AssertionError() = new()
+    AssertionError(ex) = new(ex)
+    AssertionError(ex, msg::AbstractString) = new(ex, msg)
+end
+
 # For passing constants through type inference
 immutable Val{T}
 end

base/error.jl

@@ -38,17 +38,25 @@ systemerror(p, b::Bool) = b ? throw(SystemError(string(p))) : nothing
 
 ## assertion functions and macros ##
 
-assert(x) = x ? nothing : error("assertion failed")
-macro assert(ex,msgs...)
-    msg = isempty(msgs) ? ex : msgs[1]
-    if !isempty(msgs) && isa(msg, Expr)
-        # message is an expression needing evaluating
-        msg = :(string("assertion failed: ", $(esc(msg))))
-    elseif isdefined(Base,:string)
-        msg = string("assertion failed: ", msg)
+assert(x) = x ? nothing : throw(AssertionError())
+macro assert(ex, msgs...)
+    if ex === true
+        :(nothing)
+    elseif isempty(msgs)
+        if isa(ex, Expr)
+            :($(esc(ex)) ? nothing : throw(AssertionError($(Expr(:quote,ex)))))
+        elseif ex === false
+            :(throw(AssertionError(false)))
+        else
+            :(throw(TypeError(:toplevel, "", Bool, $(esc(ex)))))
+        end
     else
-        # string() might not be defined during bootstrap
-        msg = :(string("assertion failed: ", $(Expr(:quote,msg))))
+        if isa(ex, Expr)
+            :($(esc(ex)) ? nothing : throw(AssertionError($(Expr(:quote,ex)), $(esc(msgs[1])))))
+        elseif ex === false
+            :(throw(AssertionError(false, $(esc(msgs[1])))))
+        else
+            :(throw(TypeError(:toplevel, "", Bool, $(esc(ex)))))
+        end
     end
-    :($(esc(ex)) ? $(nothing) : error($msg))
 end

base/exports.jl

@@ -158,6 +158,7 @@ export
     ProcessExitedException,
     SystemError,
     TypeError,
+    AssertionError,
 
 # Global constants and variables
     ARGS,

base/replutil.jl

@@ -123,6 +123,16 @@ showerror(io::IO, e::ErrorException) = print(io, e.msg)
 showerror(io::IO, e::KeyError) = (print(io, "key not found: "); show(io, e.key))
 showerror(io::IO, e::InterruptException) = print(io, "interrupt")
 
+function showerror(io::IO, ex::AssertionError)
+    if !isdefined(ex, :expr)
+        print(io, "AssertionError: ")
+    elseif !isdefined(ex, :msg)
+        print(io, "AssertionError: $(ex.expr)")
+    else
+        print(io, "AssertionError: $(ex.expr), $(ex.msg)")
+    end
+end
+
 function showerror(io::IO, e::MethodError)
     name = isgeneric(e.f) ? e.f.env.name : :anonymous
     if isa(e.f, DataType)

test/socket.jl

@@ -68,7 +68,8 @@ close(server)
 server = listen(port)
 @async connect("localhost",port)
 s1 = accept(server)
-@test_throws ErrorException accept(server,s1)
+#TODO: should not rely on assertions for error messages
+@test_throws AssertionError accept(server,s1)
 close(server)
 
 @test_throws Base.UVError connect(".invalid",80)