"wanna" and "gotta" can contrast with &q
"wanna" and "gotta" actually contrast with "want to" and "got to".
"Who do you want to visit"
"I want Jane to visit"
vs.
"Who do you wanna visit"
"I want to visit Jane"
And
"I gotta go" = "I have to go right now"
"I got to go" = "I had the opportunity to go."
That's true.
In more formal English, you could have "Who do you want to visit?" doing double duty, with some possible ambiguity. (The other way to clarify would be to use "Who do you wish to visit?" as a formal alternative to "Who do you wanna visit?")
The reason for this is that "wanna" and "gotta" are lexicalized irregular forms of the quasimodal forms "want to" and "got to", and are not associated with non-quasimodal uses of "want" and "got" followed by "to"; they are not due to regular phonological reduction of "want to" or "got to", which could occur if such were not actually lexicalized in nature.
<(The other way to clarify would be to use "Who do you wish to visit?" as a formal alternative to "Who do you wanna visit?") >
Only useful if one wishes to speak formally, right?
<<And
"I gotta go" = "I have to go right now"
"I got to go" = "I had the opportunity to go." >>
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"I got to go" meaning, "I had the opp. to go/I was allowed [/able] to go" (with a stress on 'got') can also mean "I must go/I have [got] to go" (with a stress on 'go'). It depends on where you emphasize the word.