improve minor inferrabilities (#42141)

base/shell.jl

@@ -49,22 +49,24 @@ function shell_parse(str::AbstractString, interpolate::Bool=true;
  empty!(innerlist)
  end
 
+ C = eltype(str)
+ P = Pair{Int,C}
  for (j, c) in st
- j, c = j::Int, c::eltype(str)
+ j, c = j::Int, c::C
  if !in_single_quotes && !in_double_quotes && isspace(c)
  i = consume_upto!(arg, s, i, j)
  append_2to1!(args, arg)
  while !isempty(st)
  # We've made sure above that we don't end in whitespace,
  # so updating `i` here is ok
- (i, c) = peek(st)::Pair{Int,eltype(str)}
+ (i, c) = peek(st)::P
  isspace(c) || break
  popfirst!(st)
  end
  elseif interpolate && !in_single_quotes && c == '$'
  i = consume_upto!(arg, s, i, j)
  isempty(st) && error("\$ right before end of command")
- stpos, c = popfirst!(st)::Pair{Int,eltype(str)}
+ stpos, c = popfirst!(st)::P
  isspace(c) && error("space not allowed right after \$")
  if startswith(SubString(s, stpos), "var\"")
  # Disallow var"#" syntax in cmd interpolations.
@@ -88,19 +90,19 @@ function shell_parse(str::AbstractString, interpolate::Bool=true;
  in_double_quotes = !in_double_quotes
  i = consume_upto!(arg, s, i, j)
  elseif !in_single_quotes && c == '\\'
- if !isempty(st) && peek(st)[2] in ('\n', '\r')
+ if !isempty(st) && (peek(st)::P)[2] in ('\n', '\r')
  i = consume_upto!(arg, s, i, j) + 1
- if popfirst!(st)[2] == '\r' && peek(st)[2] == '\n'
+ if popfirst!(st)[2] == '\r' && (peek(st)::P)[2] == '\n'
  i += 1
  popfirst!(st)
  end
- while !isempty(st) && peek(st)[2] in (' ', '\t')
+ while !isempty(st) && (peek(st)::P)[2] in (' ', '\t')
  i = nextind(str, i)
  _ = popfirst!(st)
  end
  elseif in_double_quotes
  isempty(st) && error("unterminated double quote")
- k, c′ = peek(st)
+ k, c′ = peek(st)::P
  if c′ == '"' || c′ == '$' || c′ == '\\'
  i = consume_upto!(arg, s, i, j)
  _ = popfirst!(st)

base/strings/unicode.jl

@@ -681,7 +681,7 @@ function iterate(g::GraphemeIterator, i_=(Int32(0),firstindex(g.s)))
  y === nothing && return nothing
  c0, k = y
  while k <= ncodeunits(s) # loop until next grapheme is s[i:j]
- c, ℓ = iterate(s, k)
+ c, ℓ = iterate(s, k)::NTuple{2,Any}
  isgraphemebreak!(state, c0, c) && break
  j = k
  k = ℓ