Spec: Syntax of control structures.

[Cherry-picked cbf9d42]

Author: sjrd

docs/_spec/06-expressions.md

@@ -10,9 +10,12 @@ chapter: 6
 Expr         ::=  (Bindings | id | ‘_’) ‘=>’ Expr
                |  Expr1
 Expr1        ::=  ‘if’ ‘(’ Expr ‘)’ {nl} Expr [[semi] ‘else’ Expr]
+               |  ‘if‘ Expr ‘then‘ Expr [[semi] ‘else‘ Expr]
                |  ‘while’ ‘(’ Expr ‘)’ {nl} Expr
-               |  ‘try’ Expr [‘catch’ Expr] [‘finally’ Expr]
-               |  ‘for’ (‘(’ Enumerators ‘)’ | ‘{’ Enumerators ‘}’) {nl} [‘yield’] Expr
+               |  ‘while’ Expr ‘do’ Expr
+               |  ‘try’ Expr [Catches] [‘finally’ Expr]
+               |  ‘for’ (‘(’ Enumerators ‘)’ | ‘{’ Enumerators ‘}’) {nl} [‘do‘ | ‘yield’] Expr
+               |  ‘for’ Enumerators (‘do‘ | ‘yield’) Expr
                |  ‘throw’ Expr
                |  ‘return’ [Expr]
                |  [SimpleExpr ‘.’] id ‘=’ Expr
@@ -46,6 +49,7 @@ ResultExpr   ::=  Expr1
 Ascription   ::=  ‘:’ InfixType
                |  ‘:’ Annotation {Annotation}
                |  ‘:’ ‘_’ ‘*’
+Catches      ::=  ‘catch‘ (Expr | ExprCaseClause)
 ```
 
 Expressions are composed of operators and operands.
@@ -681,6 +685,7 @@ def matmul(xss: Array[Array[Double]], yss: Array[Array[Double]]) = {
 
 ```ebnf
 Expr1          ::=  ‘if’ ‘(’ Expr ‘)’ {nl} Expr [[semi] ‘else’ Expr]
+                 |  ‘if‘ Expr ‘then‘ Expr [[semi] ‘else‘ Expr]
 ```
 
 The _conditional expression_ `if (´e_1´) ´e_2´ else ´e_3´` chooses one of the values of ´e_2´ and ´e_3´, depending on the value of ´e_1´.
@@ -700,6 +705,7 @@ The conditional expression `if (´e_1´) ´e_2´` is evaluated as if it was `if
 
 ```ebnf
 Expr1          ::=  ‘while’ ‘(’ Expr ‘)’ {nl} Expr
+                 |  ‘while’ Expr ‘do’ Expr
 ```
 
 The _while loop expression_ `while (´e_1´) ´e_2´` is typed and evaluated as if it was an application of `whileLoop (´e_1´) (´e_2´)` where the hypothetical method `whileLoop` is defined as follows.
@@ -874,15 +880,19 @@ The type of a throw expression is `scala.Nothing`.
 ## Try Expressions
 
 ```ebnf
-Expr1 ::=  ‘try’ Expr [‘catch’ Expr] [‘finally’ Expr]
+Expr1    ::=  ‘try’ Expr [Catches] [‘finally’ Expr]
+
+Catches  ::=  ‘catch‘ (Expr | ExprCaseClause)
 ```
 
-A _try expression_ is of the form `try { ´b´ } catch ´h´` where the handler ´h´ is usually a [pattern matching anonymous function](08-pattern-matching.html#pattern-matching-anonymous-functions)
+A _try expression_ is of the form `try ´b´ catch ´h´` where the handler ´h´ is usually a [pattern matching anonymous function](08-pattern-matching.html#pattern-matching-anonymous-functions)
 
 ```scala
 { case ´p_1´ => ´b_1´ ... case ´p_n´ => ´b_n´ }
 ```
 
+If the handler is a single `ExprCaseClause`, it is a shorthand for that `ExprCaseClause` wrapped in a pattern matching anonymous function.
+
 This expression is evaluated by evaluating the block ´b´.
 If evaluation of ´b´ does not cause an exception to be thrown, the result of ´b´ is returned.
 Otherwise the handler ´h´ is applied to the thrown exception.
@@ -891,22 +901,22 @@ If the handler contains no case matching the thrown exception, the exception is
 More generally, if the handler is a `PartialFunction`, it is applied only if it is defined at the given exception.
 
 Let ´\mathit{pt}´ be the expected type of the try expression.
-The block ´b´ is expected to conform to ´\mathit{pt}´.
+The expression ´b´ is expected to conform to ´\mathit{pt}´.
 The handler ´h´ is expected conform to type `scala.Function[scala.Throwable, ´\mathit{pt}\,´]`.
 The type of the try expression is the [least upper bound](03-types.html#least-upper-bounds-and-greatest-lower-bounds) of the type of ´b´ and the result type of ´h´.
 
-A try expression `try { ´b´ } finally ´e´` evaluates the block ´b´.
+A try expression `try ´b´ finally ´e´` evaluates the expression ´b´.
 If evaluation of ´b´ does not cause an exception to be thrown, the expression ´e´ is evaluated.
 If an exception is thrown during evaluation of ´e´, the evaluation of the try expression is aborted with the thrown exception.
 If no exception is thrown during evaluation of ´e´, the result of ´b´ is returned as the result of the try expression.
 
 If an exception is thrown during evaluation of ´b´, the finally block ´e´ is also evaluated.
 If another exception ´e´ is thrown during evaluation of ´e´, evaluation of the try expression is aborted with the thrown exception.
 If no exception is thrown during evaluation of ´e´, the original exception thrown in ´b´ is re-thrown once evaluation of ´e´ has completed.
-The block ´b´ is expected to conform to the expected type of the try expression.
+The expression ´b´ is expected to conform to the expected type of the try expression.
 The finally expression ´e´ is expected to conform to type `Unit`.
 
-A try expression `try { ´b´ } catch ´e_1´ finally ´e_2´` is a shorthand for  `try { try { ´b´ } catch ´e_1´ } finally ´e_2´`.
+A try expression `try ´b´ catch ´e_1´ finally ´e_2´` is a shorthand for  `try { try ´b´ catch ´e_1´ } finally ´e_2´`.
 
 ## Anonymous Functions
 

docs/_spec/08-pattern-matching.md

@@ -489,6 +489,7 @@ Therefore, the right hand side of the case clause, `y.n`, of type `Int`, is foun
   Expr            ::=  PostfixExpr ‘match’ ‘{’ CaseClauses ‘}’
   CaseClauses     ::=  CaseClause {CaseClause}
   CaseClause      ::=  ‘case’ Pattern [Guard] ‘=>’ Block
+  ExprCaseClause  ::=  ‘case’ Pattern [Guard] ‘=>’ Expr
 ```
 
 A _pattern matching expression_