From f789b9ee2b93ef0cdf80d9ef281a6ed13767fa4e Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Wed, 28 Apr 2021 00:11:24 -0400
Subject: [PATCH 01/28] Add global to store and re-display errors in the REPL

---
 base/client.jl          | 7 +++++++
 stdlib/REPL/src/REPL.jl | 1 +
 2 files changed, 8 insertions(+)

diff --git a/base/client.jl b/base/client.jl
index 375e41d3ee38f..e15cad1b64465 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -82,6 +82,12 @@ function ip_matches_func(ip, func::Symbol)
     return false
 end
 
+struct ExceptionInfo
+    errors::Vector{Tuple{Any, Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}}}
+end
+
+show(io::IO, exs::ExceptionInfo) = display_error(io, exs.errors)
+
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types
         bt = stacktrace(bt)
@@ -117,6 +123,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionInfo(lasterr))
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 9e67ad9c2d8ab..03cb6457b1e41 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,6 +284,7 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionInfo(val))
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value

From 1a6ebe7a30cb2cfefebc76828ba8ba16f8f609eb Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Wed, 28 Apr 2021 00:34:43 -0400
Subject: [PATCH 02/28] Add test

---
 stdlib/REPL/test/repl.jl | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index 3fbf6d8825bba..5599e2386f922 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1366,3 +1366,19 @@ end
         @test isempty(mods)
     end
 end
+
+# errs should reprint error
+fake_repl() do stdin_write, stdout_read, repl
+    repltask = @async begin
+        REPL.run_repl(repl)
+    end
+    write(stdin_write, "foobar\n")
+    readline(stdout_read)
+    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
+    @test readline(stdout_read) == ""
+    readuntil(stdout_read, "julia> ", keep=true)
+    write(stdin_write, "errs\n")
+    readline(stdout_read)
+    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
+    @test readline(stdout_read) == ""
+end

From e1e0beb4bcd9e166624672a7e8065f3d1493c0a6 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Wed, 28 Apr 2021 08:19:25 -0400
Subject: [PATCH 03/28] Add MIME type

---
 base/client.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/base/client.jl b/base/client.jl
index e15cad1b64465..b8c75e78cd694 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -86,7 +86,7 @@ struct ExceptionInfo
     errors::Vector{Tuple{Any, Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}}}
 end
 
-show(io::IO, exs::ExceptionInfo) = display_error(io, exs.errors)
+show(io::IO, ::MIME"text/plain", exs::ExceptionInfo) = display_error(io, exs.errors)
 
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types

From d2768a0183b545308f3874ed85a0c6600002c6f4 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 2 May 2021 21:52:24 -0400
Subject: [PATCH 04/28] Changed to ExceptionStack

---
 base/client.jl          | 8 ++------
 base/error.jl           | 4 ++++
 stdlib/REPL/src/REPL.jl | 2 +-
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index b8c75e78cd694..28278e6b1e7d4 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -82,11 +82,7 @@ function ip_matches_func(ip, func::Symbol)
     return false
 end
 
-struct ExceptionInfo
-    errors::Vector{Tuple{Any, Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}}}
-end
-
-show(io::IO, ::MIME"text/plain", exs::ExceptionInfo) = display_error(io, exs.errors)
+show(io::IO, ::MIME"text/plain", exs::ExceptionStack) = display_error(io, exs.errors)
 
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types
@@ -123,7 +119,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionInfo(lasterr))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionStack(lasterr))
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing
diff --git a/base/error.jl b/base/error.jl
index a1a7d1817d4c6..ad72975049e73 100644
--- a/base/error.jl
+++ b/base/error.jl
@@ -65,6 +65,10 @@ struct InterpreterIP
     mod::Union{Module,Nothing}
 end
 
+struct ExceptionStack
+    stack::Array{Tuple{Any, Array{Union{Ptr{Nothing}, InterpreterIP}, 1}}, 1}
+end
+
 # convert dual arrays (raw bt buffer, array of GC managed values) to a single
 # array of locations
 function _reformat_bt(bt::Array{Ptr{Cvoid},1}, bt2::Array{Any,1})
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 03cb6457b1e41..44e7352ea51a2 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,7 +284,7 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionInfo(val))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionStack(val))
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value

From a5ccf7d55f982ff2dbf9e70b329482761c1d62a6 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 2 May 2021 22:02:21 -0400
Subject: [PATCH 05/28] Fix

---
 base/client.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/base/client.jl b/base/client.jl
index 28278e6b1e7d4..e7bcb1f8c6d00 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -82,7 +82,7 @@ function ip_matches_func(ip, func::Symbol)
     return false
 end
 
-show(io::IO, ::MIME"text/plain", exs::ExceptionStack) = display_error(io, exs.errors)
+show(io::IO, ::MIME"text/plain", exs::ExceptionStack) = display_error(io, exs.stack)
 
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types

From 06122027cccec83c0c3e9d49b778eb0f4c54664b Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 2 May 2021 22:02:53 -0400
Subject: [PATCH 06/28] errs => err

---
 base/client.jl          | 2 +-
 stdlib/REPL/src/REPL.jl | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index e7bcb1f8c6d00..b82549295914c 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -119,7 +119,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionStack(lasterr))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, ExceptionStack(lasterr))
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 44e7352ea51a2..522ad79facb83 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,7 +284,7 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :errs, ExceptionStack(val))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, ExceptionStack(val))
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value

From dbb106009940aa28e622315188df5920ebafb665 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 2 May 2021 22:03:31 -0400
Subject: [PATCH 07/28] update test

---
 stdlib/REPL/test/repl.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index 5599e2386f922..cc2abc81e3268 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1367,7 +1367,7 @@ end
     end
 end
 
-# errs should reprint error
+# err should reprint error
 fake_repl() do stdin_write, stdout_read, repl
     repltask = @async begin
         REPL.run_repl(repl)
@@ -1377,7 +1377,7 @@ fake_repl() do stdin_write, stdout_read, repl
     @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
     @test readline(stdout_read) == ""
     readuntil(stdout_read, "julia> ", keep=true)
-    write(stdin_write, "errs\n")
+    write(stdin_write, "err\n")
     readline(stdout_read)
     @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
     @test readline(stdout_read) == ""

From dcd610b64b4944106472be52046afdec61198525 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 3 May 2021 00:11:21 -0400
Subject: [PATCH 08/28] Added NEWS

---
 NEWS.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 9fca99a785f3a..2fd9d73214bcf 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -103,6 +103,8 @@ Standard library changes
   argument have a type more specific than `Any`; use SHIFT-TAB instead of TAB
   to allow any compatible methods.
 
+* New `err` global variable in `Main` that is set when an expression throws an exception, akin to `ans`. Typing `err` reprints the exception information.
+
 #### SparseArrays
 
 #### Dates

From 5eb85818cc65d628ae20b78930027c25924bdda2 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 3 May 2021 14:16:18 -0400
Subject: [PATCH 09/28] bump

---
 NEWS.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index 2fd9d73214bcf..8e69c8ce3f878 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -103,7 +103,7 @@ Standard library changes
   argument have a type more specific than `Any`; use SHIFT-TAB instead of TAB
   to allow any compatible methods.
 
-* New `err` global variable in `Main` that is set when an expression throws an exception, akin to `ans`. Typing `err` reprints the exception information.
+* New `err` global variable in `Main` set when an expression throws an exception, akin to `ans`. Typing `err` reprints the exception information.
 
 #### SparseArrays
 

From 6a3e5f49726a745c076dfe666b6de9dc6cc01e3c Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Thu, 20 May 2021 15:40:14 -0400
Subject: [PATCH 10/28] Removed unnecessary extra ExceptionStack

---
 base/error.jl | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/base/error.jl b/base/error.jl
index ad72975049e73..a1a7d1817d4c6 100644
--- a/base/error.jl
+++ b/base/error.jl
@@ -65,10 +65,6 @@ struct InterpreterIP
     mod::Union{Module,Nothing}
 end
 
-struct ExceptionStack
-    stack::Array{Tuple{Any, Array{Union{Ptr{Nothing}, InterpreterIP}, 1}}, 1}
-end
-
 # convert dual arrays (raw bt buffer, array of GC managed values) to a single
 # array of locations
 function _reformat_bt(bt::Array{Ptr{Cvoid},1}, bt2::Array{Any,1})

From 370ad13289d3ffbf92b64e38a56d363eb58b80b0 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 6 Jun 2021 00:30:59 -0400
Subject: [PATCH 11/28] Fix client, which was wrapping an ExceptionStack in
 itself.

---
 base/client.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/base/client.jl b/base/client.jl
index b82549295914c..3ac23f911e564 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -119,7 +119,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, ExceptionStack(lasterr))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, lasterr)
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing

From dbf0bcc17f17ddc8781cafb00a4c4f6dd43e09bf Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 6 Jun 2021 03:57:11 -0400
Subject: [PATCH 12/28] Fix REPL to remove unnecessary Exception Stack wrapping

---
 stdlib/REPL/src/REPL.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 522ad79facb83..f38ae9bd39ade 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,7 +284,7 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, ExceptionStack(val))
+                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, val)
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value

From c83f65a8998f0b6536d3d28d1a9dc9f4641f1834 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Sun, 6 Jun 2021 04:00:41 -0400
Subject: [PATCH 13/28] Remove unnecessary unwrapping of ExceptionStack

---
 base/client.jl | 2 --
 1 file changed, 2 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index 3ac23f911e564..def745ce697cf 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -82,8 +82,6 @@ function ip_matches_func(ip, func::Symbol)
     return false
 end
 
-show(io::IO, ::MIME"text/plain", exs::ExceptionStack) = display_error(io, exs.stack)
-
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types
         bt = stacktrace(bt)

From 33299b35f5b2df57907c01a4c6b7ea4f2f72414d Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 7 Jun 2021 11:43:55 -0400
Subject: [PATCH 14/28] Corrected test

---
 stdlib/REPL/test/repl.jl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index cc2abc81e3268..ebd8890374cf7 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1379,6 +1379,7 @@ fake_repl() do stdin_write, stdout_read, repl
     readuntil(stdout_read, "julia> ", keep=true)
     write(stdin_write, "err\n")
     readline(stdout_read)
-    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
+    @test readline(stdout_read) == "\e[0m1-element ExceptionStack:"
+    @test readline(stdout_read) == "ERROR: UndefVarError: foobar not defined"
     @test readline(stdout_read) == ""
 end

From 47ce6e0a8be47bdffea32394f04568a1d9ba5715 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 7 Jun 2021 17:00:01 -0400
Subject: [PATCH 15/28] test fix

---
 stdlib/REPL/test/repl.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index ebd8890374cf7..f5d62ef83bcbf 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1381,5 +1381,5 @@ fake_repl() do stdin_write, stdout_read, repl
     readline(stdout_read)
     @test readline(stdout_read) == "\e[0m1-element ExceptionStack:"
     @test readline(stdout_read) == "ERROR: UndefVarError: foobar not defined"
-    @test readline(stdout_read) == ""
+    @test readline(stdout_read) == "Stacktrace:"
 end

From 6000b8dae5cfded96aac4801427608b8fb75edb2 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 7 Jun 2021 20:00:34 -0400
Subject: [PATCH 16/28] Testing out limiting storage of an error

---
 base/client.jl | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/base/client.jl b/base/client.jl
index def745ce697cf..c4c3e9488643a 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -95,12 +95,16 @@ end
 function display_error(io::IO, er, bt)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
     bt = scrub_repl_backtrace(bt)
+    istrivial = length(stack) == 1 && length(bt) ≤ 1 # frame 1 = top level
+    !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
     showerror(IOContext(io, :limit => true), er, bt, backtrace = bt!==nothing)
     println(io)
 end
 function display_error(io::IO, stack::ExceptionStack)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
     bt = Any[ (x[1], scrub_repl_backtrace(x[2])) for x in stack ]
+    istrivial = length(stack) == 1 && length(stack[1].backtrace) ≤ 1 # frame 1 = top level
+    !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
     show_exception_stack(IOContext(io, :limit => true), bt)
     println(io)
 end
@@ -117,7 +121,6 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, lasterr)
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing

From cfab0ef944b55330fc1a9118cf3838e3162b15ac Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 7 Jun 2021 20:01:42 -0400
Subject: [PATCH 17/28] Moved global-setting to `display_error`

---
 stdlib/REPL/src/REPL.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index f38ae9bd39ade..9e67ad9c2d8ab 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,7 +284,6 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
-                ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, val)
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value

From b33665740cdc1b1a89112dde6d2b6c4276b3ec02 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Mon, 7 Jun 2021 20:39:55 -0400
Subject: [PATCH 18/28] Test to conform with limit to storing err

---
 stdlib/REPL/test/repl.jl | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index f5d62ef83bcbf..5b6771ebe218f 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1367,7 +1367,7 @@ end
     end
 end
 
-# err should reprint error
+# err should reprint error if deeper than top-level
 fake_repl() do stdin_write, stdout_read, repl
     repltask = @async begin
         REPL.run_repl(repl)
@@ -1379,6 +1379,11 @@ fake_repl() do stdin_write, stdout_read, repl
     readuntil(stdout_read, "julia> ", keep=true)
     write(stdin_write, "err\n")
     readline(stdout_read)
+    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: err not defined"
+    readuntil(stdout_read, "julia> ", keep=true)
+    write(stdin_write, "foo() = foobar\n")
+    write(stdin_write, "foo()\n")
+    readline(stdout_read)
     @test readline(stdout_read) == "\e[0m1-element ExceptionStack:"
     @test readline(stdout_read) == "ERROR: UndefVarError: foobar not defined"
     @test readline(stdout_read) == "Stacktrace:"

From 292bc37259bc745141126886a45c379537c21de5 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Thu, 10 Jun 2021 13:22:48 -0400
Subject: [PATCH 19/28] Fix error

---
 base/client.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/base/client.jl b/base/client.jl
index c4c3e9488643a..cc332746b4482 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -95,6 +95,7 @@ end
 function display_error(io::IO, er, bt)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
     bt = scrub_repl_backtrace(bt)
+    stack = ExceptionStack([(exception = er, backtrace = bt)])
     istrivial = length(stack) == 1 && length(bt) ≤ 1 # frame 1 = top level
     !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
     showerror(IOContext(io, :limit => true), er, bt, backtrace = bt!==nothing)

From 00d5f517f3473653a965a91736d198f7622bf47c Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Thu, 10 Jun 2021 15:44:39 -0400
Subject: [PATCH 20/28] Fix for saving logic and test

---
 base/client.jl           | 6 +++---
 stdlib/REPL/test/repl.jl | 2 ++
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index cc332746b4482..b3aac21b2ef7a 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -96,17 +96,17 @@ function display_error(io::IO, er, bt)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
     bt = scrub_repl_backtrace(bt)
     stack = ExceptionStack([(exception = er, backtrace = bt)])
-    istrivial = length(stack) == 1 && length(bt) ≤ 1 # frame 1 = top level
+    istrivial = length(bt) ≤ 1 # frame 1 = top level
     !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
     showerror(IOContext(io, :limit => true), er, bt, backtrace = bt!==nothing)
     println(io)
 end
 function display_error(io::IO, stack::ExceptionStack)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
-    bt = Any[ (x[1], scrub_repl_backtrace(x[2])) for x in stack ]
+    stack = ExceptionStack([(exception = x[1], backtrace = scrub_repl_backtrace(x[2])) for x in stack ])
     istrivial = length(stack) == 1 && length(stack[1].backtrace) ≤ 1 # frame 1 = top level
     !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
-    show_exception_stack(IOContext(io, :limit => true), bt)
+    show_exception_stack(IOContext(io, :limit => true), stack)
     println(io)
 end
 display_error(stack::ExceptionStack) = display_error(stderr, stack)
diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index 5b6771ebe218f..bcc6f928b0394 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1382,6 +1382,8 @@ fake_repl() do stdin_write, stdout_read, repl
     @test readline(stdout_read) == "\e[0mERROR: UndefVarError: err not defined"
     readuntil(stdout_read, "julia> ", keep=true)
     write(stdin_write, "foo() = foobar\n")
+    readline(stdout_read)
+    readuntil(stdout_read, "julia> ", keep=true)
     write(stdin_write, "foo()\n")
     readline(stdout_read)
     @test readline(stdout_read) == "\e[0m1-element ExceptionStack:"

From 3cae5ee816df771caaf63dce956b8bbaba94c208 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Thu, 10 Jun 2021 17:04:36 -0400
Subject: [PATCH 21/28] test fixed

---
 stdlib/REPL/test/repl.jl | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index bcc6f928b0394..db138e55cbb4b 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -1372,21 +1372,34 @@ fake_repl() do stdin_write, stdout_read, repl
     repltask = @async begin
         REPL.run_repl(repl)
     end
+    # initialize `err` to `nothing`
+    write(stdin_write, "global err = nothing\n")
+    readline(stdout_read)
+    readline(stdout_read) == "\e[0m"
+    readuntil(stdout_read, "julia> ", keep=true)
+    # generate top-level error
     write(stdin_write, "foobar\n")
     readline(stdout_read)
     @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
     @test readline(stdout_read) == ""
     readuntil(stdout_read, "julia> ", keep=true)
+    # check that top-level error did not change `err`
     write(stdin_write, "err\n")
     readline(stdout_read)
-    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: err not defined"
+    @test readline(stdout_read) == "\e[0m"
     readuntil(stdout_read, "julia> ", keep=true)
+    # generate deeper error
     write(stdin_write, "foo() = foobar\n")
     readline(stdout_read)
     readuntil(stdout_read, "julia> ", keep=true)
     write(stdin_write, "foo()\n")
     readline(stdout_read)
+    @test readline(stdout_read) == "\e[0mERROR: UndefVarError: foobar not defined"
+    readuntil(stdout_read, "julia> ", keep=true)
+    # check that deeper error did set `err`
+    write(stdin_write, "err\n")
+    readline(stdout_read)
     @test readline(stdout_read) == "\e[0m1-element ExceptionStack:"
-    @test readline(stdout_read) == "ERROR: UndefVarError: foobar not defined"
+    @test readline(stdout_read) == "UndefVarError: foobar not defined"
     @test readline(stdout_read) == "Stacktrace:"
 end

From a46df33663726206149344846a198c87b1ea8487 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Tue, 12 Oct 2021 20:18:22 -0400
Subject: [PATCH 22/28] bump

---
 NEWS.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/NEWS.md b/NEWS.md
index 8e69c8ce3f878..e097d86d3289d 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -103,7 +103,8 @@ Standard library changes
   argument have a type more specific than `Any`; use SHIFT-TAB instead of TAB
   to allow any compatible methods.
 
-* New `err` global variable in `Main` set when an expression throws an exception, akin to `ans`. Typing `err` reprints the exception information.
+* New `err` global variable in `Main` set when an expression throws an exception, akin to `ans`. Typing `err` reprints
+  the exception information.
 
 #### SparseArrays
 

From 31d4bf46aa527df81eb62332004968477e824ac8 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 29 Oct 2021 01:18:30 -0400
Subject: [PATCH 23/28] Refinements

---
 base/client.jl                 | 24 ++++++++++--------------
 contrib/generate_precompile.jl |  4 +---
 stdlib/REPL/src/REPL.jl        |  6 +++++-
 stdlib/REPL/test/repl.jl       |  6 +++---
 4 files changed, 19 insertions(+), 21 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index b3aac21b2ef7a..166a748bffce7 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -84,33 +84,26 @@ end
 
 function scrub_repl_backtrace(bt)
     if bt !== nothing && !(bt isa Vector{Any}) # ignore our sentinel value types
-        bt = stacktrace(bt)
+        bt = bt isa Vector{StackFrame} ? copy(bt) : stacktrace(bt)
         # remove REPL-related frames from interactive printing
         eval_ind = findlast(frame -> !frame.from_c && frame.func === :eval, bt)
         eval_ind === nothing || deleteat!(bt, eval_ind:length(bt))
     end
     return bt
 end
+scrub_repl_backtrace(stack::ExceptionStack) =
+    ExceptionStack([(exception = x[1], backtrace = scrub_repl_backtrace(x[2])) for x in stack])
+
+istrivialerror(stack::ExceptionStack) =
+    length(stack) == 1 && length(stack[1].backtrace) ≤ 1
+    # frame 1 = top level; assumes already went through scrub_repl_backtrace
 
-function display_error(io::IO, er, bt)
-    printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
-    bt = scrub_repl_backtrace(bt)
-    stack = ExceptionStack([(exception = er, backtrace = bt)])
-    istrivial = length(bt) ≤ 1 # frame 1 = top level
-    !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
-    showerror(IOContext(io, :limit => true), er, bt, backtrace = bt!==nothing)
-    println(io)
-end
 function display_error(io::IO, stack::ExceptionStack)
     printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
-    stack = ExceptionStack([(exception = x[1], backtrace = scrub_repl_backtrace(x[2])) for x in stack ])
-    istrivial = length(stack) == 1 && length(stack[1].backtrace) ≤ 1 # frame 1 = top level
-    !istrivial && ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, stack)
     show_exception_stack(IOContext(io, :limit => true), stack)
     println(io)
 end
 display_error(stack::ExceptionStack) = display_error(stderr, stack)
-display_error(er, bt=nothing) = display_error(stderr, er, bt)
 
 function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
     errcount = 0
@@ -122,6 +115,8 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 print(color_normal)
             end
             if lasterr !== nothing
+                lasterr = scrub_repl_backtrace(lasterr)
+                istrivialerror(lasterr) || ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, lasterr)
                 invokelatest(display_error, errio, lasterr)
                 errcount = 0
                 lasterr = nothing
@@ -149,6 +144,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
             end
             errcount += 1
             lasterr = current_exceptions()
+            ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, lasterr)
             if errcount > 2
                 @error "It is likely that something important is broken, and Julia will not be able to continue normally" errcount
                 break
diff --git a/contrib/generate_precompile.jl b/contrib/generate_precompile.jl
index fbc4f837ccae4..262bf564d84e2 100644
--- a/contrib/generate_precompile.jl
+++ b/contrib/generate_precompile.jl
@@ -32,9 +32,7 @@ precompile(Tuple{typeof(Base.recursive_prefs_merge), Base.Dict{String, Any}})
 precompile(Tuple{typeof(isassigned), Core.SimpleVector, Int})
 precompile(Tuple{typeof(getindex), Core.SimpleVector, Int})
 precompile(Tuple{typeof(Base.Experimental.register_error_hint), Any, Type})
-precompile(Tuple{typeof(Base.display_error), MethodError, Vector{Union{Ptr{Nothing}, Base.InterpreterIP}}})
-precompile(Tuple{typeof(Base.display_error), ErrorException})
-precompile(Tuple{typeof(Base.display_error), BoundsError})
+precompile(Tuple{typeof(Base.display_error), ExceptionStack})
 precompile(Tuple{Core.kwftype(typeof(Type)), NamedTuple{(:sizehint,), Tuple{Int}}, Type{IOBuffer}})
 precompile(Base.CoreLogging.current_logger_for_env, (Base.CoreLogging.LogLevel, String, Module))
 precompile(Base.CoreLogging.current_logger_for_env, (Base.CoreLogging.LogLevel, Symbol, Module))
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 9e67ad9c2d8ab..7818104a35f74 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -284,6 +284,8 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
         try
             Base.sigatomic_end()
             if iserr
+                val = Base.scrub_repl_backtrace(val)
+                Base.istrivialerror(val) || ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, val)
                 Base.invokelatest(Base.display_error, errio, val)
             else
                 if val !== nothing && show_value
@@ -305,7 +307,9 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
                 println(errio) # an error during printing is likely to leave us mid-line
                 println(errio, "SYSTEM (REPL): showing an error caused an error")
                 try
-                    Base.invokelatest(Base.display_error, errio, current_exceptions())
+                    excs = current_exceptions()
+                    ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, excs)
+                    Base.invokelatest(Base.display_error, errio, excs)
                 catch e
                     # at this point, only print the name of the type as a Symbol to
                     # minimize the possibility of further errors.
diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index db138e55cbb4b..9014aad40a215 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -885,13 +885,13 @@ end
 
 # Test containers in error messages are limited #18726
 let io = IOBuffer()
-    Base.display_error(io,
-        try
+    Base.display_error(io, Base.ExceptionStack([(exception =
+        (try
             [][trues(6000)]
             @assert false
         catch e
             e
-        end, [])
+        end), backtrace = [])]))
     @test length(String(take!(io))) < 1500
 end
 

From 4fcab0ec706649548a794dd0deb123266fd972a6 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 29 Oct 2021 01:21:59 -0400
Subject: [PATCH 24/28] restore error-error scrubbing

---
 base/client.jl          | 2 +-
 stdlib/REPL/src/REPL.jl | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index 166a748bffce7..3c628675339b2 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -143,7 +143,7 @@ function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
                 @error "SYSTEM: display_error(errio, lasterr) caused an error"
             end
             errcount += 1
-            lasterr = current_exceptions()
+            lasterr = scrub_repl_backtrace(current_exceptions())
             ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, lasterr)
             if errcount > 2
                 @error "It is likely that something important is broken, and Julia will not be able to continue normally" errcount
diff --git a/stdlib/REPL/src/REPL.jl b/stdlib/REPL/src/REPL.jl
index 7818104a35f74..a450e2eb7c1bd 100644
--- a/stdlib/REPL/src/REPL.jl
+++ b/stdlib/REPL/src/REPL.jl
@@ -307,7 +307,7 @@ function print_response(errio::IO, response, show_value::Bool, have_color::Bool,
                 println(errio) # an error during printing is likely to leave us mid-line
                 println(errio, "SYSTEM (REPL): showing an error caused an error")
                 try
-                    excs = current_exceptions()
+                    excs = Base.scrub_repl_backtrace(current_exceptions())
                     ccall(:jl_set_global, Cvoid, (Any, Any, Any), Main, :err, excs)
                     Base.invokelatest(Base.display_error, errio, excs)
                 catch e

From fb8474c29841b059389906f0ec521777b96d4891 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 29 Oct 2021 14:26:17 -0400
Subject: [PATCH 25/28] More scrubbing, fixed precompile

---
 base/client.jl                 | 6 +++---
 base/task.jl                   | 4 ++--
 contrib/generate_precompile.jl | 2 +-
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index 3c628675339b2..0174ef1a23ca0 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -261,7 +261,7 @@ function exec_options(opts)
         try
             load_julia_startup()
         catch
-            invokelatest(display_error, current_exceptions())
+            invokelatest(display_error, scrub_repl_backtrace(current_exceptions()))
             !(repl || is_interactive::Bool) && exit(1)
         end
     end
@@ -295,7 +295,7 @@ function exec_options(opts)
         try
             include(Main, PROGRAM_FILE)
         catch
-            invokelatest(display_error, current_exceptions())
+            invokelatest(display_error, scrub_repl_backtrace(current_exceptions()))
             if !is_interactive::Bool
                 exit(1)
             end
@@ -497,7 +497,7 @@ function _start()
     try
         exec_options(JLOptions())
     catch
-        invokelatest(display_error, current_exceptions())
+        invokelatest(display_error, scrub_repl_backtrace(current_exceptions()))
         exit(1)
     end
     if is_interactive && get(stdout, :color, false)
diff --git a/base/task.jl b/base/task.jl
index b25197e0aadcc..74643fb916902 100644
--- a/base/task.jl
+++ b/base/task.jl
@@ -446,13 +446,13 @@ function errormonitor(t::Task)
             try # try to display the failure atomically
                 errio = IOContext(PipeBuffer(), errs::IO)
                 emphasize(errio, "Unhandled Task ")
-                display_error(errio, current_exceptions(t))
+                display_error(errio, scrub_repl_backtrace(current_exceptions(t)))
                 write(errs, errio)
             catch
                 try # try to display the secondary error atomically
                     errio = IOContext(PipeBuffer(), errs::IO)
                     print(errio, "\nSYSTEM: caught exception while trying to print a failed Task notice: ")
-                    display_error(errio, current_exceptions())
+                    display_error(errio, scrub_repl_backtrace(current_exceptions()))
                     write(errs, errio)
                     flush(errs)
                     # and then the actual error, as best we can
diff --git a/contrib/generate_precompile.jl b/contrib/generate_precompile.jl
index 262bf564d84e2..3c31c4c118c00 100644
--- a/contrib/generate_precompile.jl
+++ b/contrib/generate_precompile.jl
@@ -32,7 +32,7 @@ precompile(Tuple{typeof(Base.recursive_prefs_merge), Base.Dict{String, Any}})
 precompile(Tuple{typeof(isassigned), Core.SimpleVector, Int})
 precompile(Tuple{typeof(getindex), Core.SimpleVector, Int})
 precompile(Tuple{typeof(Base.Experimental.register_error_hint), Any, Type})
-precompile(Tuple{typeof(Base.display_error), ExceptionStack})
+precompile(Tuple{typeof(Base.display_error), Base.ExceptionStack})
 precompile(Tuple{Core.kwftype(typeof(Type)), NamedTuple{(:sizehint,), Tuple{Int}}, Type{IOBuffer}})
 precompile(Base.CoreLogging.current_logger_for_env, (Base.CoreLogging.LogLevel, String, Module))
 precompile(Base.CoreLogging.current_logger_for_env, (Base.CoreLogging.LogLevel, Symbol, Module))

From bac0089cca68c0c1c43d5bd4ef1f42bd1b288cde Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 5 Nov 2021 16:45:40 -0400
Subject: [PATCH 26/28] Restore `display_error` with note

---
 base/client.jl | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/base/client.jl b/base/client.jl
index 0174ef1a23ca0..4a5379f507fb7 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -105,6 +105,14 @@ function display_error(io::IO, stack::ExceptionStack)
 end
 display_error(stack::ExceptionStack) = display_error(stderr, stack)
 
+# these forms are depended on by packages outside Julia
+function display_error(io::IO, exception, backtrace)
+    printstyled(io, "ERROR: "; bold=true, color=Base.error_color())
+    showerror(IOContext(io, :limit => true), er, bt, backtrace = bt!==nothing)
+    println(io)
+end
+display_error(er, bt=nothing) = display_error(stderr, er, bt)
+
 function eval_user_input(errio, @nospecialize(ast), show_value::Bool)
     errcount = 0
     lasterr = nothing

From f54c85ce99b7fa31ab8d100b2d3e7068e0cc5dc8 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 5 Nov 2021 16:47:29 -0400
Subject: [PATCH 27/28] it's a named tuple

---
 base/client.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/base/client.jl b/base/client.jl
index 4a5379f507fb7..226f3fa00a61b 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -92,7 +92,7 @@ function scrub_repl_backtrace(bt)
     return bt
 end
 scrub_repl_backtrace(stack::ExceptionStack) =
-    ExceptionStack([(exception = x[1], backtrace = scrub_repl_backtrace(x[2])) for x in stack])
+    ExceptionStack([(;x.exception, backtrace = scrub_repl_backtrace(x.backtrace)) for x in stack])
 
 istrivialerror(stack::ExceptionStack) =
     length(stack) == 1 && length(stack[1].backtrace) ≤ 1

From 1e47f958be1e25bad03134664f985c0d4dc86229 Mon Sep 17 00:00:00 2001
From: Nicholas Bauer <nicholasbauer@outlook.com>
Date: Fri, 5 Nov 2021 16:57:36 -0400
Subject: [PATCH 28/28] Ensure uses Vector{Any}

Co-authored-by: Jameson Nash <vtjnash@gmail.com>
---
 base/client.jl           | 2 +-
 stdlib/REPL/test/repl.jl | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/base/client.jl b/base/client.jl
index 226f3fa00a61b..67264f96fae0e 100644
--- a/base/client.jl
+++ b/base/client.jl
@@ -92,7 +92,7 @@ function scrub_repl_backtrace(bt)
     return bt
 end
 scrub_repl_backtrace(stack::ExceptionStack) =
-    ExceptionStack([(;x.exception, backtrace = scrub_repl_backtrace(x.backtrace)) for x in stack])
+    ExceptionStack(Any[(;x.exception, backtrace = scrub_repl_backtrace(x.backtrace)) for x in stack])
 
 istrivialerror(stack::ExceptionStack) =
     length(stack) == 1 && length(stack[1].backtrace) ≤ 1
diff --git a/stdlib/REPL/test/repl.jl b/stdlib/REPL/test/repl.jl
index 9014aad40a215..e81b48f69f705 100644
--- a/stdlib/REPL/test/repl.jl
+++ b/stdlib/REPL/test/repl.jl
@@ -885,7 +885,7 @@ end
 
 # Test containers in error messages are limited #18726
 let io = IOBuffer()
-    Base.display_error(io, Base.ExceptionStack([(exception =
+    Base.display_error(io, Base.ExceptionStack(Any[(exception =
         (try
             [][trues(6000)]
             @assert false