sharpen the result of tmerge() for Tuple types

change a comprehension in Pkg.Reqs.Requirement that depended on type
inference. due to `call` constructors we simply cannot get its type
anymore, although the other change in this commit helps a lot.

base/inference.jl

@@ -1154,7 +1154,10 @@ function tmerge(typea::ANY, typeb::ANY)
  if typeb <: typea
  return typea
  end
- if typea <: Tuple && typeb <: Tuple
+ if isa(typea, Tuple) && isa(typeb, Tuple)
+ if length(typea) == length(typeb) && !isvatuple(typea) && !isvatuple(typeb)
+ return typejoin(typea, typeb)
+ end
  return Tuple
  end
  u = Union(typea, typeb)

base/pkg/reqs.jl

@@ -24,7 +24,7 @@ immutable Requirement <: Line
  package = shift!(fields)
  all(field->ismatch(Base.VERSION_REGEX, field), fields) ||
  error("invalid requires entry for $package: $content")
- versions = [VersionNumber(field) for field in fields]
+ versions = VersionNumber[fields...]
  issorted(versions) || error("invalid requires entry for $package: $content")
  new(content, package, VersionSet(versions), system)
  end