Use type wrapper directly rather than typename in FieldError

Author: MasonProtter

base/errorshow.jl

@@ -382,7 +382,7 @@ end
 
 function showerror(io::IO, exc::FieldError)
     @nospecialize
-    print(io, "FieldError: type $(exc.type |> nameof) has no field `$(exc.field)`")
+    print(io, "FieldError: type $(exc.type.name.wrapper) has no field `$(exc.field)`")
     Base.Experimental.show_error_hints(io, exc)
 end
 
@@ -1127,7 +1127,7 @@ Experimental.register_error_hint(fielderror_dict_hint_handler, FieldError)
 function fielderror_listfields_hint_handler(io, exc)
     fields = fieldnames(exc.type)
     if isempty(fields)
-        print(io, "; $(nameof(exc.type)) has no fields at all.")
+        print(io, "; $(exc.type.name.wrapper) has no fields at all.")
     else
         print(io, ", available fields: $(join(map(k -> "`$k`", fields), ", "))")
     end

test/errorshow.jl

@@ -1332,3 +1332,22 @@ let err_str
     err_str = @except_str f56325(1,2) MethodError
     @test occursin("The anonymous function", err_str)
 end
+
+@testset "FieldError with changing fields" begin
+    # https://discourse.julialang.org/t/better-error-message-for-modified-structs-in-julia-1-12/129265
+    module FieldErrorTest
+    struct Point end
+    p = Point()
+    end
+
+    err_str1 = @except_str FieldErrorTest.p.x FieldError
+    @test occursin("FieldErrorTest.Point", err_str1)
+
+    @eval FieldErrorTest struct Point{T}
+        x::T
+        y::T
+    end
+    err_str2 = @except_str FieldErrorTest.p.x FieldError
+    @test occursin("@world", err_str2)
+    @test occursin("FieldErrorTest.Point", err_str2)
+end