dmd.sideeffect

bool isTrivialExp(Expression e);

Front-end expression rewriting should create temporary variables for non trivial sub-expressions in order to:

1. save evaluation order
2. prevent sharing of sub-expression in AST

bool hasSideEffect(Expression e, bool assumeImpureCalls = false);

Determine if Expression has any side effects.

Parameters:

Expression e	the expression
bool assumeImpureCalls	whether function calls should always be assumed to be impure (e.g. debug is allowed to violate purity)

int callSideEffectLevel(FuncDeclaration f);

Determine if the call of f, or function type or delegate type t1, has any side effects.

Returns:

0 has any side effects 1 nothrow + strongly pure 2 nothrow + strongly pure + only immutable indirections in the return type

bool discardValue(Expression e);

The result of this expression will be discarded. Print error messages if the operation has no side effects (and hence is meaningless).

Returns:

true if expression has no side effects

VarDeclaration copyToTemp(StorageClass stc, const char[] name, Expression e);

Build a temporary variable to copy the value of e into.

Parameters:

StorageClass stc	storage classes will be added to the made temporary variable
char[] name	name for temporary variable
Expression e	original expression

Returns:

Newly created temporary variable.

Expression extractSideEffect(Scope* sc, const char[] name, ref Expression e0, Expression e, bool alwaysCopy = false);

Build a temporary variable to extract e's evaluation, if e is not trivial.

Parameters:

Scope* sc	scope
char[] name	name for temporary variable
Expression e0	a new side effect part will be appended to it.
Expression e	original expression
bool alwaysCopy	if true, build new temporary variable even if e is trivial.

Returns:

When e is trivial and alwaysCopy == false, e itself is returned. Otherwise, a new VarExp is returned.

Note e's lvalue-ness will be handled well by STC.ref_ or STC.rvalue.