[SR-6207] Misleading error for unqualified use of static variable in method

Previous ID	SR-6207
Radar	rdar://problem/24291352
Original Reporter	@huonw
Type	Bug
Status	In Progress
Resolution

Swift 4

Votes	0
Component/s	Compiler
Labels	Bug, DiagnosticsQoI, StarterBug
Assignee	None
Priority	Medium

md5: 47c00d1618aecdca414e977e2fbf19c9

Issue Description:

struct HasStatic {
    func foo() {
        print(cvar)
    }
    static let cvar = 123
}

hasstatic.swift:3:11: error: static member 'cvar' cannot be used on instance of type 'HasStatic'
    print(cvar)
          ^~~~
          HasStatic.

The fixit helps, but it still isn't obvious what's going wrong. The compiler is acting like the use of cvar was written self.cvar, and hints at this with "an instance of", but it's easy to gloss over the subtlety. The text could be tweaked, maybe like

static member 'cvar' can only be used on the type 'HasStatic', not the instance 'X'

where the X is the relevant parent value. (e.g. self for this case, or foo.bar for foo.bar.cvar).