improve correctness of fieldtype_tfunc

Vararg is only exact if in covariant position

also make getfield_tfunc monotonic for the case where the type has one
field, to avoid the same bug

fix #16530

(cherry picked from commit aeaff55)
ref #17953

base/inference.jl

@@ -408,7 +408,7 @@ function limit_type_depth(t::ANY, d::Int, cov::Bool, vars)
     else
         return t
     end
-    if inexact && !isvarargtype(R)
+    if inexact && (!cov || !isvarargtype(R))
         R = TypeVar(:_,R)
         push!(vars, R)
     end
@@ -467,12 +467,15 @@ function getfield_tfunc(s0::ANY, name)
             end
         end
         snames = s.name.names
-        for i=1:length(snames)
+        for i = 1:length(snames)
             if is(snames[i],fld)
                 R = s.types[i]
                 if isempty(s.parameters)
                     return R, true
                 else
+                    # conservatively limit the type depth here,
+                    # since the UnionAll type bound is otherwise incorrect
+                    # in the current type system
                     typ = limit_type_depth(R, 0, true,
                                            filter!(x->isa(x,TypeVar), Any[s.parameters...]))
                     return typ, isleaftype(s) && typeseq(typ, R)
@@ -493,8 +496,20 @@ function getfield_tfunc(s0::ANY, name)
             return Bottom, true
         end
         return s.types[i], false
+    elseif isempty(s.types)
+        return Bottom, true
+    elseif length(s.types) == 1 && isempty(s.parameters)
+        return s.types[1], true
     else
-        return reduce(tmerge, Bottom, map(unwrapva,s.types)) #=Union{s.types...}=#, false
+        R = reduce(tmerge, Bottom, map(unwrapva,s.types)) #=Union{s.types...}=#
+        # do the same limiting as the known-symbol case to preserve type-monotonicity
+        if isempty(s.parameters)
+            return R, typeseq(R, s.types[1])
+        else
+            typ = limit_type_depth(R, 0, true,
+                                   filter!(x->isa(x,TypeVar), Any[s.parameters...]))
+            return typ, isleaftype(s) && typeseq(typ, R)
+        end
     end
 end
 add_tfunc(getfield, 2, 2, (s,name)->getfield_tfunc(s,name)[1])

src/jltypes.c

@@ -83,7 +83,7 @@ static int jl_has_typevars__(jl_value_t *v, int incl_wildcard, jl_value_t **p, s
             jl_has_typevars__(((jl_tvar_t*)v)->lb, incl_wildcard, p, np))
             return 1;
         if (p != NULL) {
-            for(i=0; i < np; i++) {
+            for (i = 0; i < np; i++) {
                 if (v == p[i])
                     return 1;
             }
@@ -102,7 +102,7 @@ static int jl_has_typevars__(jl_value_t *v, int incl_wildcard, jl_value_t **p, s
     }
     else if (jl_is_datatype(v)) {
         if (is_unspec((jl_datatype_t*)v))
-            return 0;
+            return 0; // TODO: fix expect in this case
         if (p == NULL) {
             if (incl_wildcard)
                 expect = ((jl_datatype_t*)v)->haswildcard;
@@ -118,7 +118,7 @@ static int jl_has_typevars__(jl_value_t *v, int incl_wildcard, jl_value_t **p, s
         return 0;
     }
     size_t l = jl_svec_len(t);
-    for(i=0; i < l; i++) {
+    for (i = 0; i < l; i++) {
         jl_value_t *elt = jl_svecref(t, i);
         if (elt != v) {
             if (jl_has_typevars__(elt, incl_wildcard, p, np)) {

test/inference.jl

@@ -282,3 +282,27 @@ let I = Integer[]
     push!(I, 1)
     @test I == Any[1]
 end
+
+# issue #16530
+type Foo16530a{dim}
+    c::Vector{NTuple{dim, Float64}}
+    d::Vector
+end
+type Foo16530b{dim}
+    c::Vector{NTuple{dim, Float64}}
+end
+f16530a() = fieldtype(Foo16530a, :c)
+f16530a(c) = fieldtype(Foo16530a, c)
+f16530b() = fieldtype(Foo16530b, :c)
+f16530b(c) = fieldtype(Foo16530b, c)
+
+let T = Array{Tuple{Vararg{Float64,TypeVar(:dim)}},1},
+    TTlim = Type{TypeVar(:_,Array{TypeVar(:_,Tuple),1})}
+
+    @test f16530a() == T
+    @test f16530a(:c) == T
+    @test Base.return_types(f16530a, ()) == Any[TTlim]
+    @test Base.return_types(f16530b, ()) == Any[TTlim]
+    @test Base.return_types(f16530b, (Symbol,)) == Any[TTlim]
+end
+@test f16530a(:d) == Vector