Support !!foo as a double-negation

compiler/frontend/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java

@@ -64,7 +64,9 @@ public class JetExpressionParsing extends AbstractJetParsing {
 
     /*package*/ static final TokenSet EXPRESSION_FIRST = TokenSet.create(
             // Prefix
-            MINUS, PLUS, MINUSMINUS, PLUSPLUS, EXCL, LBRACKET, LABEL_IDENTIFIER, AT, ATAT,
+            MINUS, PLUS, MINUSMINUS, PLUSPLUS,
+            EXCL, EXCLEXCL, // Joining complex tokens makes it necessary to put EXCLEXCL here
+            LBRACKET, LABEL_IDENTIFIER, AT, ATAT,
             // Atomic
 
             LPAR, // parenthesized
@@ -325,24 +327,34 @@ public class JetExpressionParsing extends AbstractJetParsing {
      */
     private void parsePrefixExpression() {
 //        System.out.println("pre at "  + myBuilder.getTokenText());
+
         if (at(LBRACKET)) {
             if (!parseLocalDeclaration()) {
                 PsiBuilder.Marker expression = mark();
                 myJetParsing.parseAnnotations(false);
                 parsePrefixExpression();
                 expression.done(ANNOTATED_EXPRESSION);
-            } else {
+            }
+            else {
                 return;
             }
-        } else if (atSet(Precedence.PREFIX.getOperations())) {
-            PsiBuilder.Marker expression = mark();
+        }
+        else {
+            myBuilder.disableJoiningComplexTokens();
+            if (atSet(Precedence.PREFIX.getOperations())) {
+                PsiBuilder.Marker expression = mark();
 
-            parseOperationReference();
+                parseOperationReference();
 
-            parsePrefixExpression();
-            expression.done(PREFIX_EXPRESSION);
-        } else {
-            parsePostfixExpression();
+                myBuilder.restoreJoiningComplexTokensState();
+
+                parsePrefixExpression();
+                expression.done(PREFIX_EXPRESSION);
+            }
+            else {
+                myBuilder.restoreJoiningComplexTokensState();
+                parsePostfixExpression();
+            }
         }
     }
 

compiler/frontend/src/org/jetbrains/jet/lang/parsing/SemanticWhitespaceAwarePsiBuilderImpl.java

@@ -32,7 +32,7 @@ import static org.jetbrains.jet.lexer.JetTokens.*;
  * @author abreslav
  */
 public class SemanticWhitespaceAwarePsiBuilderImpl extends PsiBuilderAdapter implements SemanticWhitespaceAwarePsiBuilder {
-    private final TokenSet complexTokens = TokenSet.create(SAFE_ACCESS, ELVIS);
+    private final TokenSet complexTokens = TokenSet.create(SAFE_ACCESS, ELVIS, EXCLEXCL);
     private final Stack<Boolean> joinComplexTokens = new Stack<Boolean>();
 
     private final Stack<Boolean> newlinesEnabled = new Stack<Boolean>();
@@ -126,6 +126,10 @@ public class SemanticWhitespaceAwarePsiBuilderImpl extends PsiBuilderAdapter imp
             if (nextRawToken == DOT) return SAFE_ACCESS;
             if (nextRawToken == COLON) return ELVIS;
         }
+        else if (rawTokenType == EXCL) {
+            IElementType nextRawToken = rawLookup(rawLookupSteps);
+            if (nextRawToken == EXCL) return EXCLEXCL;
+        }
         return rawTokenType;
     }
 

compiler/frontend/src/org/jetbrains/jet/lexer/Jet.flex

@@ -270,7 +270,7 @@ LONG_TEMPLATE_ENTRY_END=\}
 ">="         { return JetTokens.GTEQ      ; }
 "=="         { return JetTokens.EQEQ      ; }
 "!="         { return JetTokens.EXCLEQ    ; }
-"!!"         { return JetTokens.EXCLEXCL  ; }
+//"!!"         { return JetTokens.EXCLEXCL  ; }
 "&&"         { return JetTokens.ANDAND    ; }
 "||"         { return JetTokens.OROR      ; }
 //"?."         { return JetTokens.SAFE_ACCESS;}