Several ADT improvements (#687)

* fixed reordering issue, type of constructors, implicit conversion of argument, some incorrect handling of imported adts, conversion issues with ghost data types, name space conflicts with adt types. I changed the representation of adt types, which I still need to double check.

* fixed some issues

* adapted parser to parse adts without field names

* fixed some bugs, also fixed error message with duplicate fields and clauses for adts

* fixed intendation, added comment, removed todo

build.sbt

@@ -34,7 +34,7 @@ lazy val gobra = (project in file("."))
     libraryDependencies += "org.apache.commons" % "commons-lang3" % "3.9", // for SystemUtils
     libraryDependencies += "org.apache.commons" % "commons-text" % "1.9", // for escaping strings in parser preprocessor
     libraryDependencies += "commons-codec" % "commons-codec" % "1.15", // for obtaining the hex encoding of a string
-    libraryDependencies += "org.antlr" % "antlr4-runtime" % "4.12.0",
+    libraryDependencies += "org.antlr" % "antlr4-runtime" % "4.13.0",
     libraryDependencies += "org.scalaz" %% "scalaz-core" % "7.3.7", // used for EitherT
 
     scalacOptions ++= Seq(

src/main/antlr4/GobraParser.g4

@@ -150,7 +150,9 @@ domainClause: FUNC IDENTIFIER signature | AXIOM L_CURLY expression eos R_CURLY;
 
 adtType: ADT L_CURLY (adtClause eos)* R_CURLY;
 
-adtClause: IDENTIFIER L_CURLY (fieldDecl eos)* R_CURLY;
+adtClause: IDENTIFIER L_CURLY (adtFieldDecl eos)* R_CURLY;
+
+adtFieldDecl: identifierList? type_;
 
 ghostSliceType: GHOST L_BRACKET R_BRACKET elementType;