Error Lab

Every diagnostic below is the real output of ptc, not a mock-up. Pick a mistake, read how the compiler teaches the canonical form, then flip to the fix.

let greeting = "Hello, " + "world"

error: there is no '+' on Text — concatenate with interpolation: "{a}{b}" (line 1, column 16)

let who = "world"
let greeting = "Hello, {who}"
print(greeting)

Hello, world