AssignmentsAreExpressions is probably defined somewhere else on this wiki, please tell me where.
Anyway, they are the property of the assignment (x = y) or (x := y) returning a value.

CeeLanguage has AssignmentsAreExpressions; z = (x = y) * 2 is OK in C.

AssignmentsAreExpressions are sometimes ConsideredHarmful, because of the common noob mistake made with them:
 if (x = 1) {
	/* always do this */
 } else {
	/* never do this */
 }
... even though they ''intended''
  if (x ''=='' 1)
''Experienced C* developers often learn to favor:''
  if(1 == x)
''based on the notion that the compiler will catch it for them if they make a typographical error:''
  if(1 = x)
[Just by the way, "experienced" C* developers don't create this problem for themselves in the first place.]
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GoLanguage splits the difference admirably.
 x := 1  #  initialize new var x
 x = 2  #  stick 2 into preexisting var x
 3 == x  #  returns false
Question - is ''if x := 1'' valid in Go?
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Java also has this to an extent, though the entire expression within a conditional needs to ultimately return a boolean.  The expression
 while((c = System.in.read()) != -1)
     /* Do something if not at end of input. */
will work.
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CategoryCodingIssues