5.1 General rules

Almost everything is an expression: a block { … } returns the value of its last expression (or ()), if and match are expressions.
Operands and arguments are evaluated left to right. Exception: &&, ||, ??, ?. evaluate the right operand only when necessary.
Assignments (=, +=, etc.) are statements and have no value. The left-hand side MUST be a mutable place: a var variable, a field or an index through &var.
An empty block is {}, an empty map is {:}. A { in expression position followed by expression : starts a Map literal.

Related diagnostics