add tuple type printing with Vararg, and port to static_show (JuliaLang#44970)

Author: JeffBezanson

base/show.jl

@@ -993,19 +993,31 @@ function show_datatype(io::IO, x::DataType, wheres::Vector{TypeVar}=TypeVar[])
     istuple = x.name === Tuple.name
     n = length(parameters)
 
-    # Print homogeneous tuples with more than 3 elements compactly as NTuple{N, T}
+    # Print tuple types with homogeneous tails longer than max_n compactly using `NTuple` or `Vararg`
+    max_n = 3
     if istuple
-        if n > 3 && all(@nospecialize(i) -> (parameters[1] === i), parameters)
+        taillen = 1
+        for i in (n-1):-1:1
+            if parameters[i] === parameters[n]
+                taillen += 1
+            else
+                break
+            end
+        end
+        if n == taillen > max_n
             print(io, "NTuple{", n, ", ")
             show(io, parameters[1])
             print(io, "}")
         else
             print(io, "Tuple{")
-            # join(io, params, ", ") params but `show` it
-            first = true
-            for param in parameters
-                first ? (first = false) : print(io, ", ")
-                show(io, param)
+            for i = 1:(taillen > max_n ? n-taillen : n)
+                i > 1 && print(io, ", ")
+                show(io, parameters[i])
+            end
+            if taillen > max_n
+                print(io, ", Vararg{")
+                show(io, parameters[n])
+                print(io, ", ", taillen, "}")
             end
             print(io, "}")
         end

src/rtutils.c

@@ -785,6 +785,37 @@ static size_t jl_static_show_x_(JL_STREAM *out, jl_value_t *v, jl_datatype_t *vt
         jl_sym_t *sym = globfunc ? globname : dv->name->name;
         char *sn = jl_symbol_name(sym);
         size_t quote = 0;
+        if (dv->name == jl_tuple_typename) {
+            if (dv == jl_tuple_type)
+                return jl_printf(out, "Tuple");
+            int taillen = 1, tlen = jl_nparams(dv), i;
+            for (i = tlen-2; i >= 0; i--) {
+                if (jl_tparam(dv, i) == jl_tparam(dv, tlen-1))
+                    taillen++;
+                else
+                    break;
+            }
+            if (taillen == tlen && taillen > 3) {
+                n += jl_printf(out, "NTuple{%d, ", tlen);
+                n += jl_static_show_x(out, jl_tparam0(dv), depth);
+                n += jl_printf(out, "}");
+            }
+            else {
+                n += jl_printf(out, "Tuple{");
+                for (i = 0; i < (taillen > 3 ? tlen-taillen : tlen); i++) {
+                    if (i > 0)
+                        n += jl_printf(out, ", ");
+                    n += jl_static_show_x(out, jl_tparam(dv, i), depth);
+                }
+                if (taillen > 3) {
+                    n += jl_printf(out, ", Vararg{");
+                    n += jl_static_show_x(out, jl_tparam(dv, tlen-1), depth);
+                    n += jl_printf(out, ", %d}", taillen);
+                }
+                n += jl_printf(out, "}");
+            }
+            return n;
+        }
         if (globfunc) {
             n += jl_printf(out, "typeof(");
         }
@@ -804,9 +835,7 @@ static size_t jl_static_show_x_(JL_STREAM *out, jl_value_t *v, jl_datatype_t *vt
                 n += jl_printf(out, ")");
             }
         }
-        if (dv->parameters && (jl_value_t*)dv != dv->name->wrapper &&
-            (jl_has_free_typevars(v) ||
-             (jl_value_t*)dv != (jl_value_t*)jl_tuple_type)) {
+        if (dv->parameters && (jl_value_t*)dv != dv->name->wrapper) {
             size_t j, tlen = jl_nparams(dv);
             if (tlen > 0) {
                 n += jl_printf(out, "{");
@@ -818,9 +847,6 @@ static size_t jl_static_show_x_(JL_STREAM *out, jl_value_t *v, jl_datatype_t *vt
                 }
                 n += jl_printf(out, "}");
             }
-            else if (dv->name == jl_tuple_typename) {
-                n += jl_printf(out, "{}");
-            }
         }
     }
     else if (vt == jl_intrinsic_type) {

test/show.jl

@@ -1338,6 +1338,8 @@ test_repr("(:).a")
 @test repr(NTuple{7,Int64}) == "NTuple{7, Int64}"
 @test repr(Tuple{Float64, Float64, Float64, Float64}) == "NTuple{4, Float64}"
 @test repr(Tuple{Float32, Float32, Float32}) == "Tuple{Float32, Float32, Float32}"
+@test repr(Tuple{String, Int64, Int64, Int64}) == "Tuple{String, Int64, Int64, Int64}"
+@test repr(Tuple{String, Int64, Int64, Int64, Int64}) == "Tuple{String, Vararg{Int64, 4}}"
 
 @testset "issue #42931" begin
     @test repr(NTuple{4, :A}) == "NTuple{4, :A}"