implement parsing, AST, and basic Sema support for 'defer'.

SILGen support and diagnosing jumps out of a defer aren't done
yet.



Swift SVN r27759

include/swift/AST/DiagnosticsParse.def

@@ -728,6 +728,10 @@ ERROR(expected_close_after_else,stmt_parsing,none,
 ERROR(expected_expr_return,stmt_parsing,PointsToFirstBadToken,
       "expected expression in 'return' statement", ())
 
+// Defer Statement
+ERROR(expected_lbrace_after_defer,stmt_parsing,PointsToFirstBadToken,
+      "expected '{' after 'defer'", ())
+
 // If/While Conditions
 ERROR(expected_expr_conditional_letbinding,stmt_parsing,none,
       "expected 'let' or 'var' in conditional", ())

include/swift/AST/Stmt.h

@@ -175,6 +175,32 @@ public:
   
   static bool classof(const Stmt *S) { return S->getKind() == StmtKind::Return;}
 };
+  
+/// DeferStmt - A 'defer' statement.  This runs the substatement it contains
+/// when the enclosing scope is exited.
+///
+///    defer { cleanUp() }
+///
+class DeferStmt : public Stmt {
+  SourceLoc DeferLoc;
+  BraceStmt *Body;
+  
+public:
+  DeferStmt(SourceLoc DeferLoc, BraceStmt *Body)
+    : Stmt(StmtKind::Defer, /*implicit*/false),
+  DeferLoc(DeferLoc), Body(Body) {}
+  
+  SourceLoc getDeferLoc() const { return DeferLoc; }
+  
+  SourceLoc getStartLoc() const { return DeferLoc; }
+  SourceLoc getEndLoc() const;
+  
+  BraceStmt *getBody() const { return Body; }
+  void setBody(BraceStmt *body) { Body = body; }
+  
+  static bool classof(const Stmt *S) { return S->getKind() == StmtKind::Defer; }
+};
+ 
 
   
 /// This represents an entry in an "if" or "while" condition.  Pattern bindings

include/swift/AST/StmtNodes.def

@@ -42,6 +42,7 @@
 
 STMT(Brace, Stmt)
 STMT(Return, Stmt)
+STMT(Defer, Stmt)
 ABSTRACT_STMT(Labeled, Stmt)
   ABSTRACT_STMT(LabeledConditional, LabeledStmt)
     LABELED_STMT(If, LabeledConditionalStmt)

include/swift/Parse/Parser.h

@@ -1153,6 +1153,7 @@ public:
   ParserResult<Stmt> parseStmtBreak();
   ParserResult<Stmt> parseStmtContinue();
   ParserResult<Stmt> parseStmtReturn();
+  ParserResult<Stmt> parseStmtDefer();
   ParserStatus parseStmtCondition(StmtCondition &Result, Diag<> ID);
   ParserResult<Stmt> parseStmtIf(LabeledStmtInfo LabelInfo);
   ParserResult<Stmt> parseStmtIfConfig(BraceItemListKind Kind

include/swift/Parse/Tokens.def

@@ -73,6 +73,7 @@ KEYWORD(sil_witness_table) // This is only enabled when parsing .sil files.
 KEYWORD(sil_coverage_map)  // This is only enabled when parsing .sil files.
 
 // Statement keywords.
+STMT_KEYWORD(defer)
 STMT_KEYWORD(if)
 STMT_KEYWORD(do)
 STMT_KEYWORD(repeat)