Test this change out locally with the following install scripts (Action run 29834720488)

Can we add a test case for this? I just tested it with your fix, but seems it's failing:

shared.bicepparam:

using none
param external = externalInput('foo', 'bar')
param B = {
  parent: 'parent'
}

main.bicepparam:

using 'main.bicep'

extends 'shared.bicepparam'
param B = {
  ...base.external
  something: 'something'
}

Can we add a test case for this? I just tested it with your fix, but seems it's failing:

@levimatheri I've added the regression test and fixed dependency tracking for selected base parameters containing externalInput.

I moved ProcessInlinableSymbol from a local function inside VisitVariableAccessSyntax to a private method so the same dependency propagation logic can also be reused by VisitPropertyAccessSyntax.

This allows base.external to mark the dependent assignment for inlining and emit the expected externalInputs(...) expression.