Pathological import symbol shadowing

[Paul Backus]

On Wednesday, 18 November 2020 at 01:11:35 UTC, Walter Bright 
wrote:
>> It's not just rejects-valid either, this issue has 
>> accepts-invalid cases:
>> 
>> ---
>> import std.stdio;
>> 
>> string readAndLog(string filename){
>>      import std.file;
>>      auto text=readText(filename);
>>      write(filename," read successfully!\n");
>>      return text;
>> }
>> 
>> void main(){
>>      writeln(readAndLog("important_data.txt"));
>> }
>> ---
>
> Please elaborate on what is invalid about it? Don't make me 
> guess!

Because std.file is imported locally, the call to write calls 
std.file.write instead of std.stdio.write, and overwrites 
important_data.txt.

If `import std.file` is moved to module scope, the compiler 
correctly diagnoses that the call is ambiguous.