Aliases aren’t available on the same line or in the same function where they are defined.
From the Bash man page:
The rules concerning the definition and use of aliases are somewhat
confusing. Bash always reads at least one complete line of input
before executing any of the commands on that line. Aliases are
expanded when a command is read, not when it is executed. Therefore,
an alias definition appearing on the same line as another command does
not take effect until the next line of input is read. The commands
following the alias definition on that line are not affected by the new
alias. This behavior is also an issue when functions are executed.
Aliases are expanded when a function definition is read, not when the
function is executed, because a function definition is itself a com‐
pound command. As a consequence, aliases defined in a function are not
available until after that function is executed. To be safe, always
put alias definitions on a separate line, and do not use alias in com‐
pound commands.
For almost every purpose, aliases are superseded by shell functions.
The Bash Reference Manual says
For almost every purpose, shell functions are preferred over aliases.
instead of the last sentence above [emphasis mine]. I consider aliases to be a command-line convenience rather than something that should be used in scripts (including those which consist solely of bash -c one-liners).