This issue was originally filed by [email protected]

It is a de facto standard, introduced with the shell and taken for granted in other languages that use dollar for expansion (PHP as the main example), that single quotes prevent all expansion.

The example:
  print('fib(20) = ${fib(20)}');
therefore exhibits an unconventional behavior in that it will expand the expression inside dollar-preceeded-brackets.

I would expect Dart to behave more conventionally by requiring double-quotes for inner string expansion, or single-quotes with concatenation.