allow "else if (...) then" in expressions #3609

typechecker/Ceylon.g

@@ -1163,10 +1163,7 @@ unambiguousType
  ;
 
 statement returns [Statement statement]
- : /*(IF_CLAUSE conditions THEN_CLAUSE) => 
- expressionOrSpecificationStatement
- { $statement = $expressionOrSpecificationStatement.statement; }
- |*/ directiveStatement
+ : directiveStatement
  { $statement = $directiveStatement.directive; }
  | controlStatement
  { $statement = $controlStatement.controlStatement; }
@@ -2092,10 +2089,17 @@ thenElseClauses returns [IfClause ifClause, ElseClause elseClause, ConditionList
  (
  ELSE_CLAUSE
  { $elseClause = new ElseClause($ELSE_CLAUSE); }
- de2=disjunctionExpression
- { Expression e = new Expression(null);
- e.setTerm($de2.term);
- $elseClause.setExpression(e); }
+ (
+ de2=disjunctionExpression
+ { Expression e = new Expression(null);
+ e.setTerm($de2.term);
+ $elseClause.setExpression(e); }
+ | 
+ ifExpression
+ { Expression e = new Expression(null);
+ e.setTerm($ifExpression.term);
+ $elseClause.setExpression(e); }
+ )
  )?
  ;
 
@@ -2211,15 +2215,6 @@ thenElseExpression returns [Term term]
  de2=disjunctionExpression
  { $thenElseOperator.operator.setRightTerm($de2.term); }
  )*
- //TODO: enable this to add support for if (...) and 
- // given (...) expressions
- //TODO: when enabling this, we'll need something
- // to distinguish between "if (...) then" and 
- // the control structure "if (...) { ... }"
- /*| 
- IF_CLAUSE conditions
- THEN_CLAUSE disjunctionExpression
- (ELSE_CLAUSE disjunctionExpression)?*/
  ;
 
 thenElseOperator returns [BinaryOperatorExpression operator]

typechecker/en/modules/expressions.xml

@@ -1443,12 +1443,13 @@ Digit{1,2} ":" Digit{2} ( ":" Digit{2} ( ":" Digit{3} )? )?
  <literal>then</literal> expression, and an <literal>else</literal> 
  expression. The <literal>else</literal> expression is not optional.</para>
 
- <synopsis>IfElseExpression: "if" ConditionList ThenExpression ElseExpression</synopsis>
+ <synopsis>IfElseExpression: "if" ConditionList ThenExpression (ElseExpression | ElseIfExpression)</synopsis>
+ <synopsis>ElseIfExpression: "else" IfExpression</synopsis>
 
  <para>The type of an <literal>if/then/else</literal> expression with
  <literal>then</literal> expression of type <literal>X</literal> and
- <literal>else</literal> expression of type <literal>Y</literal> is
- <literal>X|Y</literal>.</para>
+ <literal>else</literal> or <literal>else if</literal> expression of 
+ type <literal>Y</literal> is <literal>X|Y</literal>.</para>
 
  <para>A <literal>switch/case/else</literal> expression has a 
  <literal>switch</literal> expression or inline variable, a list of 

typechecker/test/main/inline/inlineExpressions.ceylon

@@ -1,5 +1,10 @@
 void inlineExpressions(Integer? arg, Boolean bool, Integer|Float num) {
 
+ @type:"String" value numStr = 
+ if (num==0) then "zero" 
+ else if (num==1) then "unit" 
+ else num.string;
+
  @type:"Integer|Float" value someStuff 
  = if (exists arg) 
  then arg else 0.0;