Please tell me this is a bug?

[Almighty Bob via Digitalmars-d]

On Sunday, 22 February 2015 at 01:32:16 UTC, Adam D. Ruppe wrote:
> On Sunday, 22 February 2015 at 01:24:09 UTC, Almighty Bob wrote:
>> Please tell me that's a bug?
>
> Nope, a is clearly an int in the last case so no conversion is 
> needed.

a is an int in all three cases, b is a float in all three cases.

In one case the compiler automatically converts b to an int 
before adding it to a. In the other two cases it gives an error. 
So..

a=a+b;
a+=b;

Are not the same, OK, it seems odd that a "shorthand" version of 
an expression would have slightly different semantics than the 
longhand version but fundamentally what bothers me is any 
automatic conversion from float to int. It should never be 
automatic.

Ok I looked up the docs, and they say...

http://dlang.org/expression.html

"Assign Expressions:
The right operand is implicitly converted to the type of the left 
operand"

which quite clearly is not the case since...

a=b; // causes an error. but..
a+=b; // does not.