add test cases and fixup completion code

stdlib/REPL/src/REPLCompletions.jl

@@ -135,9 +135,8 @@ function appendmacro!(syms, macros, needle, endchar)
     end
 end
 
-function filtered_mod_names(ffunc::Function, mod::Module, name::AbstractString;
-                            all::Bool=false, imported::Bool=false, usings::Bool=false)
-    ssyms = names(mod, all = all, imported = imported, usings = usings)
+function filtered_mod_names(ffunc::Function, mod::Module, name::AbstractString; kwargs...)
+    ssyms = names(mod; kwargs...)
     all || filter!(Base.Fix1(Base.isexported, mod), ssyms) # TODO revisit
     filter!(ffunc, ssyms)
     macros = filter(x -> startswith(String(x), "@" * name), ssyms)
@@ -182,14 +181,14 @@ function complete_symbol(@nospecialize(ex), name::String, @nospecialize(ffunc),
         end
         # Looking for a binding in a module
         if mod == context_module
-            # Also look in modules we got through `using`
-            mods = ccall(:jl_module_usings, Any, (Any,), context_module)::Vector
-            for m in mods
-                append!(suggestions, filtered_mod_names(p, m::Module, name)
-            end
-            append!(suggestions, filtered_mod_names(p, mod, name, all=true, imported=true, usings=true))
-        else
-            append!(suggestions, filtered_mod_names(p, mod, name, all=true, usings=true))
+            # special case `Core` and `Base` bindings
+            # - `Core` bindings should be added to every modules
+            # - `Base` bindings should be added to non-bare modules
+            append!(suggestions, filtered_mod_names(p, Core, name))
+            isdefined(mod, :Base) && append!(suggestions, filtered_mod_names(p, Base, name))
+            append!(suggestions, filtered_mod_names(p, mod, name; all=true, imported=true, usings=true))
+        else # dot-accessed module context
+            append!(suggestions, filtered_mod_names(p, mod, name; all=true, usings=true))
         end
     elseif val !== nothing # looking for a property of an instance
         try

stdlib/REPL/test/replcompletions.jl

@@ -2260,3 +2260,40 @@ let s = "Issue53126()."
     @test res
     @test isempty(c)
 end
+
+@testset "complete names from `using`" begin
+    test_complete_context1(args...; kwargs...) = first(test_complete_context(args...; kwargs...))
+
+    let # should work for arbitrary module
+        M = Module()
+
+        use = @eval M module use end
+        @eval use module def; foo = 42; end
+
+        @assert count(==("foo"), test_complete_context1("f", use)) ≠ 1
+        @assert count(==("foo"), test_complete_context1("use.f", M)) ≠ 1
+        @eval use using .def: foo
+        @test count(==("foo"), test_complete_context1("f", use)) == 1
+        @test count(==("foo"), test_complete_context1("use.f", M)) == 1 # should work for even dot-accessed module context
+    end
+
+    let # should work for packages
+        M = Module()
+
+        @assert count(==("fuzzyscore"), test_complete_context1("fuzzy", M)) ≠ 1
+        @eval M using REPL: fuzzyscore
+        @test count(==("fuzzyscore"), test_complete_context1("fuzzy", M)) == 1
+
+        @assert count(==("completions"), test_complete_context1("comp", M)) ≠ 1
+        @eval M using REPL.REPLCompletions: completions
+        @test count(==("completions"), test_complete_context1("comp", M)) == 1
+    end
+
+    let # should for `Base` binding
+        M = Module()
+
+        @assert count(==("@aggressive_constprop"), test_complete_context1("@aggressive_", M)) ≠ 1
+        @eval M using Base: @aggressive_constprop
+        @test count(==("@aggressive_constprop"), test_complete_context1("@aggressive_", M)) == 1
+    end
+end