Ambiguity parsing operators with suffixes ending in subscript/superscript letter

[moble]

Per this discussion, there's an ambiguity in an expression like 1 +ᵃx — which could mean either 1 +ᵃ x or 1 + ᵃx. As of this writing, the manual says (emphasis mine)

A space is required between an operator that ends with a subscript/superscript letter and a subsequent variable name. For example, if +ᵃ is an operator, then +ᵃx must be written as +ᵃ x to distinguish it from + ᵃx where ᵃx is the variable name.

Those emphasized words would suggest that a missing space would raise an error, just as 1.+x does — but that is not the case. The current behavior in both the native Julia parser and in JuliaSyntax is to parse +ᵃx as +ᵃ x. @stevengj suggests it should be an error.

[stevengj]

In particular, this loop

JuliaSyntax.jl/src/julia/tokenize.jl

Lines 433 to 436 in 4a983f6

	while isopsuffix(peekchar(l))
	readchar(l)
	suffix = true
	end

should generate an error if is_identifier_start_char returns true for both the last suffix char and the first char after that.