[antlr-interest] simple question regarding type propogation

[William Halliburton]

given an AST like such and the required transformation

(+ 1 2)  -> numericalAdd(1,2)
(+ "a" "b") -> stringConcat("a",b")

this is easy for simple additions but does not work for nested additions
because the type of results are not easily distinguishable from the AST

what is needed is

(+ (+ 1 2) (+ 3 4)) -> numericalAdd(numericalAdd(1,2),numericalAdd(3,4))

is there a way to have the tree parser run down the children and propagate
the types upwards?

thank you very much,
will


simplified grammar is below.

mathOperation
options {backtrack=true;}
    : ^('+' expression stringVal) ->
stringConcat(left={$expression.st},right={$stringVal.st})
    | ^('+' expression numberVal) ->
numericaAdd(right={$numberVal.st},left={$expression.st)})
    ;
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