add more support for vhdl2008: aliases, visibility and preliminary work for

generic packages.

14 files changed, 748 insertions, 235 deletions

diff --git a/disp_tree.adb b/disp_tree.adb
index 40a949c..a14030b 100644
--- a/disp_tree.adb
+++ b/disp_tree.adb
@@ -699,6 +699,11 @@ package body Disp_Tree is
             Disp_Tree_Flat (Get_Package (Tree), Ntab);
             Header ("declaration:");
             Disp_Tree_Chain (Get_Declaration_Chain (Tree), Ntab);
+         when Iir_Kind_Package_Header =>
+            Header ("generic chain:");
+            Disp_Tree_Chain (Get_Generic_Chain (Tree), Ntab);
+            Header ("generic map aspect chain:");
+            Disp_Tree_Chain (Get_Generic_Map_Aspect_Chain (Tree), Ntab);
          when Iir_Kind_Architecture_Declaration =>
             if Flat_Decl then
                return;
@@ -720,6 +725,15 @@ package body Disp_Tree is
             Header ("block_configuration:");
             Disp_Tree (Get_Block_Configuration (Tree), Ntab, True);
 
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            if Flat_Decl then
+               return;
+            end if;
+            Header ("uninstantiated_name:");
+            Disp_Tree_Flat (Get_Uninstantiated_Name (Tree), Ntab);
+            Header ("generic map aspect chain:");
+            Disp_Tree_Chain (Get_Generic_Map_Aspect_Chain (Tree), Ntab);
+
          when Iir_Kind_Entity_Aspect_Entity =>
             Header ("entity:");
             Disp_Tree_Flat (Get_Entity (Tree), Ntab);
diff --git a/disp_vhdl.adb b/disp_vhdl.adb
index fd75ea0..0b4627a 100644
--- a/disp_vhdl.adb
+++ b/disp_vhdl.adb
@@ -210,7 +210,9 @@ package body Disp_Vhdl is
             Put (".");
             Disp_Ident (Get_Suffix_Identifier (Name));
          when Iir_Kind_Type_Declaration
+           | Iir_Kind_Subtype_Declaration
            | Iir_Kind_Enumeration_Literal
+           | Iir_Kind_Unit_Declaration
            | Iir_Kind_Implicit_Function_Declaration
            | Iir_Kind_Implicit_Procedure_Declaration
            | Iir_Kind_Variable_Declaration
diff --git a/errorout.adb b/errorout.adb
index cd7f4f7..404c91f 100644
--- a/errorout.adb
+++ b/errorout.adb
@@ -605,6 +605,12 @@ package body Errorout is
                     & '(' & Iirs_Utils.Image_Identifier (Arch) & ')';
                end if;
             end;
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            return Disp_Identifier (Node, "instantiation package");
+
+         when Iir_Kind_Package_Header =>
+            return "package header";
+
          when Iir_Kind_Component_Declaration =>
             return Disp_Identifier (Node, "component");
 
diff --git a/iirs.adb b/iirs.adb
index 5f057ed..c628e40 100644
--- a/iirs.adb
+++ b/iirs.adb
@@ -381,6 +381,7 @@ package body Iirs is
            | Iir_Kind_Nature_Declaration
            | Iir_Kind_Subnature_Declaration
            | Iir_Kind_Configuration_Declaration
+           | Iir_Kind_Package_Declaration
            | Iir_Kind_Package_Body
            | Iir_Kind_Attribute_Declaration
            | Iir_Kind_Group_Template_Declaration
@@ -514,8 +515,9 @@ package body Iirs is
            | Iir_Kind_Subtype_Definition
            | Iir_Kind_Scalar_Nature_Definition
            | Iir_Kind_Entity_Declaration
-           | Iir_Kind_Package_Declaration
            | Iir_Kind_Architecture_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration
+           | Iir_Kind_Package_Header
            | Iir_Kind_Unit_Declaration
            | Iir_Kind_Library_Declaration
            | Iir_Kind_Component_Declaration
@@ -2247,7 +2249,7 @@ package body Iirs is
       case Get_Kind (Target) is
          when Iir_Kind_Block_Header
            | Iir_Kind_Entity_Declaration
-           | Iir_Kind_Package_Declaration
+           | Iir_Kind_Package_Header
            | Iir_Kind_Component_Declaration
            | Iir_Kind_Function_Declaration
            | Iir_Kind_Implicit_Function_Declaration
@@ -2971,7 +2973,8 @@ package body Iirs is
            | Iir_Kind_Entity_Declaration
            | Iir_Kind_Package_Declaration
            | Iir_Kind_Package_Body
-           | Iir_Kind_Architecture_Declaration =>
+           | Iir_Kind_Architecture_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration =>
             null;
          when others =>
             Failed ("Design_Unit", Target);
@@ -3434,6 +3437,7 @@ package body Iirs is
            | Iir_Kind_Package_Declaration
            | Iir_Kind_Package_Body
            | Iir_Kind_Architecture_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration
            | Iir_Kind_Unit_Declaration
            | Iir_Kind_Library_Declaration
            | Iir_Kind_Component_Declaration
@@ -3569,6 +3573,7 @@ package body Iirs is
            | Iir_Kind_Entity_Declaration
            | Iir_Kind_Package_Declaration
            | Iir_Kind_Architecture_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration
            | Iir_Kind_Unit_Declaration
            | Iir_Kind_Library_Declaration
            | Iir_Kind_Component_Declaration
@@ -4948,7 +4953,8 @@ package body Iirs is
       case Get_Kind (Target) is
          when Iir_Kind_Block_Header
            | Iir_Kind_Binding_Indication
-           | Iir_Kind_Package_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration
+           | Iir_Kind_Package_Header
            | Iir_Kind_Function_Declaration
            | Iir_Kind_Implicit_Function_Declaration
            | Iir_Kind_Implicit_Procedure_Declaration
@@ -5295,6 +5301,28 @@ package body Iirs is
       Set_Field6 (Block, Conf);
    end Set_Block_Block_Configuration;
 
+   procedure Check_Kind_For_Package_Header (Target : Iir) is
+   begin
+      case Get_Kind (Target) is
+         when Iir_Kind_Package_Declaration =>
+            null;
+         when others =>
+            Failed ("Package_Header", Target);
+      end case;
+   end Check_Kind_For_Package_Header;
+
+   function Get_Package_Header (Pkg : Iir) return Iir_Package_Body is
+   begin
+      Check_Kind_For_Package_Header (Pkg);
+      return Get_Field5 (Pkg);
+   end Get_Package_Header;
+
+   procedure Set_Package_Header (Pkg : Iir; Header : Iir_Package_Body) is
+   begin
+      Check_Kind_For_Package_Header (Pkg);
+      Set_Field5 (Pkg, Header);
+   end Set_Package_Header;
+
    procedure Check_Kind_For_Block_Header (Target : Iir) is
    begin
       case Get_Kind (Target) is
@@ -5317,6 +5345,28 @@ package body Iirs is
       Set_Field7 (Target, Header);
    end Set_Block_Header;
 
+   procedure Check_Kind_For_Uninstantiated_Name (Target : Iir) is
+   begin
+      case Get_Kind (Target) is
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            null;
+         when others =>
+            Failed ("Uninstantiated_Name", Target);
+      end case;
+   end Check_Kind_For_Uninstantiated_Name;
+
+   function Get_Uninstantiated_Name (Inst : Iir) return Iir is
+   begin
+      Check_Kind_For_Uninstantiated_Name (Inst);
+      return Get_Field1 (Inst);
+   end Get_Uninstantiated_Name;
+
+   procedure Set_Uninstantiated_Name (Inst : Iir; Name : Iir) is
+   begin
+      Check_Kind_For_Uninstantiated_Name (Inst);
+      Set_Field1 (Inst, Name);
+   end Set_Uninstantiated_Name;
+
    procedure Check_Kind_For_Generate_Block_Configuration (Target : Iir) is
    begin
       case Get_Kind (Target) is
@@ -5463,6 +5513,7 @@ package body Iirs is
            | Iir_Kind_Package_Declaration
            | Iir_Kind_Package_Body
            | Iir_Kind_Architecture_Declaration
+           | Iir_Kind_Package_Instantiation_Declaration
            | Iir_Kind_Component_Declaration
            | Iir_Kind_Attribute_Declaration
            | Iir_Kind_Group_Template_Declaration
diff --git a/iirs.ads b/iirs.ads
index 0d08929..e6541ac 100644
--- a/iirs.ads
+++ b/iirs.ads
@@ -664,7 +664,13 @@ package Iirs is
    --
    --   Get/Set_Visible_Flag (Flag4)
 
-   -- Iir_Kind_Package_Declaration (Medium)
+   -- Iir_Kind_Package_Header (Medium)
+   --
+   --   Get/Set_Generic_Chain (Field6)
+   --
+   --   Get/Set_Generic_Map_Aspect_Chain (Field8)
+
+   -- Iir_Kind_Package_Declaration (Short)
    --
    --   Get/Set_Parent (Field0)
    --   Get/Set_Design_Unit (Alias Field0)
@@ -675,11 +681,9 @@ package Iirs is
    --
    --   Get/Set_Identifier (Field3)
    --
-   --   Get/Set_Generic_Chain (Field6)
-   --
    --   Get/Set_Attribute_Value_Chain (Field4)
    --
-   --   Get/Set_Generic_Map_Aspect_Chain (Field8)
+   --   Get/Set_Package_Header (Field5)
    --
    --   Get/Set_Need_Body (Flag1)
    --
@@ -699,6 +703,19 @@ package Iirs is
    -- The corresponding package declaration.
    --   Get/Set_Package (Field4)
 
+   -- Iir_Kind_Package_Instantiation_Declaration (Medium)
+   --
+   --   Get/Set_Parent (Field0)
+   --   Get/Set_Design_Unit (Alias Field0)
+   --
+   --   Get/Set_Uninstantiated_Name (Field1)
+   --
+   --   Get/Set_Identifier (Field3)
+   --
+   --   Get/Set_Generic_Map_Aspect_Chain (Field8)
+   --
+   --   Get/Set_Visible_Flag (Flag4)
+
    -- Iir_Kind_Library_Declaration (Medium)
    --
    -- Design files in the library.
@@ -2826,11 +2843,13 @@ package Iirs is
        Iir_Kind_Subtype_Declaration,
        Iir_Kind_Nature_Declaration,
        Iir_Kind_Subnature_Declaration,
-       Iir_Kind_Configuration_Declaration,
-       Iir_Kind_Entity_Declaration,
-       Iir_Kind_Package_Declaration,
-       Iir_Kind_Package_Body,
-       Iir_Kind_Architecture_Declaration,
+       Iir_Kind_Configuration_Declaration,      -- Library_Unit
+       Iir_Kind_Entity_Declaration,             -- Library_Unit
+       Iir_Kind_Package_Declaration,            -- Library_Unit
+       Iir_Kind_Package_Body,                   -- Library_Unit
+       Iir_Kind_Architecture_Declaration,       -- Library_Unit
+       Iir_Kind_Package_Instantiation_Declaration,
+       Iir_Kind_Package_Header,
        Iir_Kind_Unit_Declaration,
        Iir_Kind_Library_Declaration,
        Iir_Kind_Component_Declaration,
@@ -2847,10 +2866,10 @@ package Iirs is
        Iir_Kind_Through_Quantity_Declaration,
 
        Iir_Kind_Function_Body,
-       Iir_Kind_Function_Declaration,
-       Iir_Kind_Implicit_Function_Declaration,
-       Iir_Kind_Implicit_Procedure_Declaration,
-       Iir_Kind_Procedure_Declaration,
+       Iir_Kind_Function_Declaration,            --  Subprg, Func
+       Iir_Kind_Implicit_Function_Declaration,   --  Subprg, Func, Imp_Subprg
+       Iir_Kind_Implicit_Procedure_Declaration,  --  Subprg, Proc, Imp_Subprg
+       Iir_Kind_Procedure_Declaration,           --  Subprg, Proc
        Iir_Kind_Procedure_Body,
        Iir_Kind_Enumeration_Literal,
 
@@ -3379,7 +3398,8 @@ package Iirs is
    --Iir_Kind_Entity_Declaration
    --Iir_Kind_Package_Declaration
    --Iir_Kind_Package_Body
-     Iir_Kind_Architecture_Declaration;
+   --Iir_Kind_Architecture_Declaration
+     Iir_Kind_Package_Instantiation_Declaration;
 
    --  Note: does not include iir_kind_enumeration_literal since it is
    --  considered as a declaration.
@@ -3529,6 +3549,10 @@ package Iirs is
    --Iir_Kind_Implicit_Procedure_Declaration
      Iir_Kind_Procedure_Declaration;
 
+   subtype Iir_Kinds_Implicit_Subprogram_Declaration is Iir_Kind range
+     Iir_Kind_Implicit_Function_Declaration ..
+     Iir_Kind_Implicit_Procedure_Declaration;
+
    subtype Iir_Kinds_Process_Statement is Iir_Kind range
      Iir_Kind_Sensitized_Process_Statement ..
      Iir_Kind_Process_Statement;
@@ -3743,6 +3767,8 @@ package Iirs is
    --Iir_Kind_Package_Declaration
    --Iir_Kind_Package_Body
    --Iir_Kind_Architecture_Declaration
+   --Iir_Kind_Package_Instantiation_Declaration
+   --Iir_Kind_Package_Header
    --Iir_Kind_Unit_Declaration
    --Iir_Kind_Library_Declaration
    --Iir_Kind_Component_Declaration
@@ -5120,10 +5146,18 @@ package Iirs is
    function Get_Block_Block_Configuration (Block : Iir) return Iir;
    procedure Set_Block_Block_Configuration (Block : Iir; Conf : Iir);
 
+   --  Field: Field5
+   function Get_Package_Header (Pkg : Iir) return Iir_Package_Body;
+   procedure Set_Package_Header (Pkg : Iir; Header : Iir_Package_Body);
+
    --  Field: Field7
    function Get_Block_Header (Target : Iir) return Iir;
    procedure Set_Block_Header (Target : Iir; Header : Iir);
 
+   --  Field: Field1
+   function Get_Uninstantiated_Name (Inst : Iir) return Iir;
+   procedure Set_Uninstantiated_Name (Inst : Iir; Name : Iir);
+
    --  Get/Set the block_configuration (there may be several
    --  block_configuration through the use of prev_configuration singly linked
    --  list) that apply to this generate statement.
diff --git a/iirs_utils.adb b/iirs_utils.adb
index fa69e8e..060c3f7 100644
--- a/iirs_utils.adb
+++ b/iirs_utils.adb
@@ -860,6 +860,37 @@ package body Iirs_Utils is
       end loop;
    end Is_Signal_Object;
 
+   --  LRM08 4.7 Package declarations
+   --  If the package header is empty, the package declared by a package
+   --  declaration is called a simple package.
+   function Is_Simple_Package (Pkg : Iir) return Boolean is
+   begin
+      return Get_Package_Header (Pkg) = Null_Iir;
+   end Is_Simple_Package;
+
+   --  LRM08 4.7 Package declarations
+   --  If the package header contains a generic clause and no generic map
+   --  aspect, the package is called an uninstantiated package.
+   function Is_Uninstantiated_Package (Pkg : Iir) return Boolean
+   is
+      Header : constant Iir := Get_Package_Header (Pkg);
+   begin
+      return Header /= Null_Iir
+        and then Get_Generic_Map_Aspect_Chain (Header) = Null_Iir;
+   end Is_Uninstantiated_Package;
+
+   --  LRM08 4.7 Package declarations
+   --  If the package header contains both a generic clause and a generic
+   --  map aspect, the package is declared a generic-mapped package.
+   function Is_Generic_Mapped_Package (Pkg : Iir) return Boolean
+   is
+      Header : constant Iir := Get_Package_Header (Pkg);
+   begin
+      return Header /= Null_Iir
+        and then Get_Generic_Map_Aspect_Chain (Header) /= Null_Iir;
+   end Is_Generic_Mapped_Package;
+
+
    function Get_HDL_Node (N : PSL_Node) return Iir is
    begin
       return Iir (PSL.Nodes.Get_HDL_Node (N));
diff --git a/iirs_utils.ads b/iirs_utils.ads
index 8061cba..1477d8e 100644
--- a/iirs_utils.ads
+++ b/iirs_utils.ads
@@ -150,6 +150,12 @@ package Iirs_Utils is
    --  See also Evaluation.Get_Physical_Value.
    function Get_Physical_Literal_Value (Lit : Iir) return Iir_Int64;
 
+   --  Definitions from LRM08 4.7 Package declarations.
+   --  PKG must denote a package declaration.
+   function Is_Simple_Package (Pkg : Iir) return Boolean;
+   function Is_Uninstantiated_Package (Pkg : Iir) return Boolean;
+   function Is_Generic_Mapped_Package (Pkg : Iir) return Boolean;
+
    --  Return TRUE if the base name of NAME is a signal object.
    function Is_Signal_Object (Name: Iir) return Boolean;
 
diff --git a/libraries.adb b/libraries.adb
index e48707d..a9efb0a 100644
--- a/libraries.adb
+++ b/libraries.adb
@@ -142,7 +142,8 @@ package body Libraries is
          when Iir_Kind_Entity_Declaration
            | Iir_Kind_Configuration_Declaration
            | Iir_Kind_Package_Declaration
-           | Iir_Kind_Package_Body =>
+           | Iir_Kind_Package_Body
+           | Iir_Kind_Package_Instantiation_Declaration =>
             Id := Get_Identifier (Lib_Unit);
          when Iir_Kind_Architecture_Declaration =>
             --  Architectures are put with the entity identifier.
@@ -1225,7 +1226,8 @@ package body Libraries is
                   WR (Image_Identifier (Library_Unit));
                   WR (" of ");
                   WR (Image_Identifier (Get_Entity (Library_Unit)));
-               when Iir_Kind_Package_Declaration =>
+               when Iir_Kind_Package_Declaration
+                 | Iir_Kind_Package_Instantiation_Declaration =>
                   WR ("package ");
                   WR (Image_Identifier (Library_Unit));
                when Iir_Kind_Package_Body =>
@@ -1576,12 +1578,16 @@ package body Libraries is
          then
             case Get_Kind (Get_Library_Unit (Unit)) is
                when Iir_Kind_Package_Declaration
+                 | Iir_Kind_Package_Instantiation_Declaration
                  | Iir_Kind_Entity_Declaration
                  | Iir_Kind_Configuration_Declaration =>
                   --  Only return a primary unit.
                   return Unit;
-               when others =>
+               when Iir_Kind_Package_Body
+                 | Iir_Kind_Architecture_Declaration =>
                   null;
+               when others =>
+                  raise Internal_Error;
             end case;
          end if;
          Unit := Get_Hash_Chain (Unit);
diff --git a/libraries/Makefile.inc b/libraries/Makefile.inc
index 5d48c40..fed7457 100644
--- a/libraries/Makefile.inc
+++ b/libraries/Makefile.inc
@@ -55,12 +55,15 @@ ieee2008/numeric_bit.vhdl \
 ieee2008/numeric_bit_unsigned.vhdl ieee2008/numeric_bit_unsigned-body.vhdl \
 ieee2008/numeric_std.vhdl \
 ieee2008/numeric_std-body.vhdl \
-ieee2008/numeric_std_unsigned.vhdl ieee2008/numeric_std_unsigned-body.vhdl
+ieee2008/numeric_std_unsigned.vhdl ieee2008/numeric_std_unsigned-body.vhdl \
+ieee2008/fixed_float_types.vhdl \
+ieee2008/fixed_generic_pkg.vhdl \
+ieee2008/fixed_pkg.vhdl
 # ieee2008/numeric_bit-body.vhdl \
-#ieee2008/fixed_float_types.vhdl
+#
 #ieee2008/fixed_generic_pkg-body.vhdl
-#ieee2008/fixed_generic_pkg.vhdl
-#ieee2008/fixed_pkg.vhdl
+
+#
 #ieee2008/float_generic_pkg-body.vhdl
 #ieee2008/float_generic_pkg.vhdl
 #ieee2008/float_pkg.vhdl
diff --git a/parse.adb b/parse.adb
index df8ce38..9e16404 100644
--- a/parse.adb
+++ b/parse.adb
@@ -190,6 +190,16 @@ package body Parse is
       end loop;
    end Eat_Tokens_Until_Semi_Colon;
 
+   --  Expect and scan ';' emit an error message using MSG if not present.
+   procedure Scan_Semi_Colon (Msg : String) is
+   begin
+      if Current_Token /= Tok_Semi_Colon then
+         Error_Msg_Parse ("missing "";"" at end of " & Msg);
+      else
+         Scan;
+      end if;
+   end Scan_Semi_Colon;
+
    --  precond : next token
    --  postcond: next token.
    --
@@ -1175,21 +1185,17 @@ package body Parse is
          El := Get_Chain (El);
       end loop;
 
-      if Current_Token /= Tok_Semi_Colon then
-         Error_Msg_Parse ("missing "";"" at end of port clause");
-      else
-         Scan;
-      end if;
+      Scan_Semi_Colon ("port clause");
       Set_Port_Chain (Parent, Res);
    end Parse_Port_Clause;
 
    --  precond : GENERIC
    --  postcond: next token
    --
-   --  [ §1.1.1 ]
+   --  [ LRM93 1.1.1, LRM08 6.5.6.2 ]
    --  generic_clause ::= GENERIC ( generic_list ) ;
    --
-   --  [ §1.1.1.1]
+   --  [ LRM93 1.1.1.1, LRM08 6.5.6.2]
    --  generic_list ::= GENERIC_interface_list
    procedure Parse_Generic_Clause (Parent : Iir)
    is
@@ -1203,12 +1209,9 @@ package body Parse is
       Scan;
       Res := Parse_Interface_Chain
         (Iir_Kind_Constant_Interface_Declaration, Parent);
-      if Current_Token /= Tok_Semi_Colon then
-         Error_Msg_Parse ("missing "";"" at end of generic clause");
-      else
-         Scan;
-      end if;
       Set_Generic_Chain (Parent, Res);
+
+      Scan_Semi_Colon ("generic clause");
    end Parse_Generic_Clause;
 
    --  precond : a token.
@@ -1462,17 +1465,25 @@ package body Parse is
    begin
       Res := Create_Iir (Iir_Kind_Physical_Type_Definition);
       Set_Location (Res);
+
+      --  Eat 'units'
       Expect (Tok_Units);
       Scan;
+
       --  Parse primary unit.
       Expect (Tok_Identifier);
       Unit := Create_Iir (Iir_Kind_Unit_Declaration);
       Set_Location (Unit);
       Set_Identifier (Unit, Current_Identifier);
+
+      --  Skip identifier
+      Scan;
+
+      Scan_Semi_Colon ("primary unit");
+
       Build_Init (Last);
       Append (Last, Res, Unit);
-      Scan_Expect (Tok_Semi_Colon);
-      Scan;
+
       --  Parse secondary units.
       while Current_Token /= Tok_End loop
          Unit := Create_Iir (Iir_Kind_Unit_Declaration);
@@ -1490,8 +1501,7 @@ package body Parse is
                Error_Msg_Parse ("a physical literal is expected here");
          end case;
          Append (Last, Res, Unit);
-         Expect (Tok_Semi_Colon);
-         Scan;
+         Scan_Semi_Colon ("secondary unit");
       end loop;
       Scan;
       Expect (Tok_Units);
@@ -1555,8 +1565,7 @@ package body Parse is
          Subtype_Indication := Parse_Subtype_Indication;
          Set_Type (First, Subtype_Indication);
          First := Null_Iir;
-         Expect (Tok_Semi_Colon);
-         Scan;
+         Scan_Semi_Colon ("element declaration");
          exit when Current_Token = Tok_End;
       end loop;
       Scan_Expect (Tok_Record);
@@ -4810,21 +4819,31 @@ package body Parse is
                   end if;
                   Build_Init (Last_Assoc);
                   while Current_Token /= Tok_End loop
+                     --  Eat 'when'
                      Expect (Tok_When);
                      Scan;
+
                      if Current_Token = Tok_Double_Arrow then
                         Error_Msg_Parse ("missing expression in alternative");
+                        Assoc := Create_Iir (Iir_Kind_Choice_By_Expression);
+                        Set_Location (Assoc);
                      else
                         Assoc := Parse_Choices (Null_Iir);
                      end if;
+
+                     --  Eat '=>'
                      Expect (Tok_Double_Arrow);
                      Scan;
+
                      Set_Associated
                        (Assoc, Parse_Sequential_Statements (Stmt));
                      Append_Subchain (Last_Assoc, Stmt, Assoc);
                   end loop;
+
+                  --  Eat 'end', 'case'
                   Scan_Expect (Tok_Case);
                   Scan;
+
                   if Flags.Vhdl_Std >= Vhdl_93c then
                      Check_End_Name (Stmt);
                   end if;
@@ -4845,8 +4864,7 @@ package body Parse is
                Set_Label (Stmt, Label);
             end if;
          end if;
-         Expect (Tok_Semi_Colon);
-         Scan;
+         Scan_Semi_Colon ("statement");
 
          --  Append it to the chain.
          if First_Stmt = Null_Iir then
@@ -5247,7 +5265,7 @@ package body Parse is
    --  precond : GENERIC
    --  postcond: next token
    --
-   --  [ §5.2.1.2 ]
+   --  [ LRM93 5.2.1.2, LRM08 6.5.7.2 ]
    --  generic_map_aspect ::= GENERIC MAP ( GENERIC_association_list )
    function Parse_Generic_Map_Aspect return Iir is
    begin
@@ -5354,16 +5372,14 @@ package body Parse is
          Parse_Generic_Clause (Res);
          if Current_Token = Tok_Generic then
             Set_Generic_Map_Aspect_Chain (Res, Parse_Generic_Map_Aspect);
-            Expect (Tok_Semi_Colon);
-            Scan;
+            Scan_Semi_Colon ("generic map aspect");
          end if;
       end if;
       if Current_Token = Tok_Port then
          Parse_Port_Clause (Res);
          if Current_Token = Tok_Port then
             Set_Port_Map_Aspect_Chain (Res, Parse_Port_Map_Aspect);
-            Expect (Tok_Semi_Colon);
-            Scan;
+            Scan_Semi_Colon ("port map aspect");
          end if;
       end if;
       return Res;
@@ -6106,8 +6122,7 @@ package body Parse is
            | Tok_Generic
            | Tok_Port =>
             Set_Binding_Indication (Res, Parse_Binding_Indication);
-            Expect (Tok_Semi_Colon);
-            Scan;
+            Scan_Semi_Colon ("binding indication");
          when others =>
             null;
       end case;
@@ -6361,26 +6376,50 @@ package body Parse is
       Set_Library_Unit (Unit, Res);
    end Parse_Configuration_Declaration;
 
-   --  precond : identifier
+   --  precond : generic
+   --  postcond: next token
+   --
+   --  LRM08 4.7
+   --  package_header ::=
+   --      [ generic_clause               -- LRM08 6.5.6.2
+   --      [ generic_map aspect ; ] ]
+   function Parse_Package_Header return Iir
+   is
+      Res : Iir;
+   begin
+      Res := Create_Iir (Iir_Kind_Package_Header);
+      Parse_Generic_Clause (Res);
+
+      if Current_Token = Tok_Generic then
+         Set_Generic_Map_Aspect_Chain (Res, Parse_Generic_Map_Aspect);
+         Scan_Semi_Colon ("generic map aspect");
+      end if;
+      return Res;
+   end Parse_Package_Header;
+
+   --  precond : token (after 'IS')
    --  postcond: ';'
    --
-   --  [ §2.5 ]
+   --  [ LRM93 2.5, LRM08 4.7 ]
    --  package_declaration ::=
    --      PACKAGE identifier IS
+   --          package_header           -- LRM08
    --          package_declarative_part
    --      END [ PACKAGE ] [ PACKAGE_simple_name ] ;
-   procedure Parse_Package_Declaration (Unit : Iir_Design_Unit)
+   procedure Parse_Package_Declaration (Unit : Iir_Design_Unit; Id : Name_Id)
    is
       Res: Iir_Package_Declaration;
    begin
       Res := Create_Iir (Iir_Kind_Package_Declaration);
       Set_Location (Res);
+      Set_Identifier (Res, Id);
 
-      -- Get identifier.
-      Expect (Tok_Identifier);
-      Set_Identifier (Res, Current_Identifier);
-      Scan_Expect (Tok_Is);
-      Scan;
+      if Current_Token = Tok_Generic then
+         if Vhdl_Std < Vhdl_08 then
+            Error_Msg_Parse ("generic packages not allowed before vhdl 2008");
+         end if;
+         Set_Package_Header (Res, Parse_Package_Header);
+      end if;
 
       Parse_Declarative_Part (Res);
 
@@ -6401,7 +6440,7 @@ package body Parse is
    --  precond : BODY
    --  postcond: ';'
    --
-   --  [ §2.6 ]
+   --  [ LRM93 2.6, LRM08 4.8 ]
    --  package_body ::=
    --      PACKAGE BODY PACKAGE_simple_name IS
    --          package_body_declarative_part
@@ -6436,6 +6475,76 @@ package body Parse is
       Set_Library_Unit (Unit, Res);
    end Parse_Package_Body;
 
+   --  precond : NEW
+   --  postcond: ';'
+   --
+   --  [ LRM08 4.9 ]
+   --  package_instantiation_declaration ::=
+   --      PACKAGE identifier IS NEW uninstantiated_package_name
+   --         [ generic_map_aspect ] ;
+   function Parse_Package_Instantiation_Declaration
+     (Id : Name_Id; Loc : Location_Type)
+     return Iir
+   is
+      Res: Iir;
+   begin
+      Res := Create_Iir (Iir_Kind_Package_Instantiation_Declaration);
+      Set_Location (Res, Loc);
+      Set_Identifier (Res, Id);
+
+      --  Skip 'new'
+      Scan;
+
+      Set_Uninstantiated_Name (Res, Parse_Name (False));
+
+      if Current_Token = Tok_Generic then
+         Set_Generic_Map_Aspect_Chain (Res, Parse_Generic_Map_Aspect);
+      end if;
+
+      Expect (Tok_Semi_Colon);
+
+      return Res;
+   end Parse_Package_Instantiation_Declaration;
+
+   --  precond : PACKAGE
+   --  postcond: ';'
+   --
+   --    package_declaration
+   --  | package_body
+   --  | package_instantiation_declaration
+   procedure Parse_Package (Unit : Iir_Design_Unit)
+   is
+      Loc : constant Location_Type := Get_Token_Location;
+      Id : Name_Id;
+   begin
+      --  Skip 'package'
+      Scan;
+
+      if Current_Token = Tok_Body then
+         --  Skip 'body'
+         Scan;
+
+         Parse_Package_Body (Unit);
+      else
+         Expect (Tok_Identifier);
+         Id := Current_Identifier;
+         Scan;
+
+         Expect (Tok_Is);
+         Scan;
+
+         if Current_Token = Tok_New then
+            Set_Library_Unit
+              (Unit,
+               Parse_Package_Instantiation_Declaration (Id, Loc));
+            --  Note: there is no 'end' in instantiation.
+            Set_End_Location (Unit, Get_Token_Location);
+         else
+            Parse_Package_Declaration (Unit, Id);
+         end if;
+      end if;
+   end Parse_Package;
+
    -- Parse a design_unit.
    -- The lexical scanner must have been initialized, but without a
    -- current_token.
@@ -6502,13 +6611,7 @@ package body Parse is
          when Tok_Architecture =>
             Parse_Architecture (Res);
          when Tok_Package =>
-            Scan;
-            if Current_Token = Tok_Body then
-               Scan;
-               Parse_Package_Body (Res);
-            else
-               Parse_Package_Declaration (Res);
-            end if;
+            Parse_Package (Res);
          when Tok_Configuration =>
             Parse_Configuration_Declaration (Res);
          when others =>
diff --git a/sem.adb b/sem.adb
index a785137..2aef995 100644
--- a/sem.adb
+++ b/sem.adb
@@ -334,22 +334,25 @@ package body Sem is
       return True;
    end Can_Collapse_Signals;
 
-   --  INTER_PARENT contains generics and ports interfaces;
-   --  ASSOC_PARENT constains generics and ports map aspects.
-   procedure Sem_Generic_Port_Association_Chain
+   --  INTER_PARENT contains generics interfaces;
+   --  ASSOC_PARENT constains generic aspects.
+   procedure Sem_Generic_Association_Chain
      (Inter_Parent : Iir; Assoc_Parent : Iir)
    is
       El : Iir;
-      Actual : Iir;
-      Prefix : Iir;
-      Object : Iir;
       Match : Boolean;
       Assoc_Chain : Iir;
-      Miss_Generic : Missing_Type;
-      Miss_Port : Missing_Type;
-      Inter : Iir;
-      Formal : Iir;
+      Miss : Missing_Type;
    begin
+      --  LRM08 6.5.6.2 Generic clauses
+      --  If no such actual is specified for a given formal generic constant
+      --  (either because the formal generic is unassociated or because the
+      --  actual is open), and if a default expression is specified for that
+      --  generic, the value of this expression is the value of the generic.
+      --  It is an error if no actual is specified for a given formal generic
+      --  constant and no default expression is present in the corresponding
+      --  interface element.
+
       --  Note: CHECK_MATCH argument of sem_subprogram_arguments must be
       --   true if parent is a component instantiation.
       case Get_Kind (Assoc_Parent) is
@@ -366,22 +369,22 @@ package body Sem is
             if Flags.Vhdl_Std = Vhdl_87
               or else Get_Kind (Inter_Parent) = Iir_Kind_Entity_Declaration
             then
-               Miss_Generic := Missing_Generic;
-               Miss_Port := Missing_Port;
+               Miss := Missing_Generic;
             else
-               Miss_Generic := Missing_Allowed;
-               Miss_Port := Missing_Allowed;
+               Miss := Missing_Allowed;
             end if;
          when Iir_Kind_Binding_Indication =>
             --  LRM 5.2.1.2  Generic map and port map aspects
-            Miss_Generic := Missing_Allowed;
-            Miss_Port := Missing_Allowed;
+            Miss := Missing_Allowed;
          when Iir_Kind_Block_Header =>
-            --  FIXME: it is possible to have port unassociated ?
-            Miss_Generic := Missing_Generic;
-            Miss_Port := Missing_Port;
+            Miss := Missing_Generic;
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            --  LRM08 4.9
+            --  Each formal generic (or member thereof) shall be associated
+            --  at most once.
+            Miss := Missing_Generic;
          when others =>
-            Error_Kind ("sem_generic_port_association_list", Assoc_Parent);
+            Error_Kind ("sem_generic_association_list", Assoc_Parent);
       end case;
 
       --  The generics
@@ -389,7 +392,7 @@ package body Sem is
       if Sem_Actual_Of_Association_Chain (Assoc_Chain) then
          Sem_Association_Chain
            (Get_Generic_Chain (Inter_Parent), Assoc_Chain,
-            True, Miss_Generic, Assoc_Parent, Match);
+            True, Miss, Assoc_Parent, Match);
          Set_Generic_Map_Aspect_Chain (Assoc_Parent, Assoc_Chain);
 
          --  LRM 5.2.1.2   Generic map and port map aspects
@@ -406,13 +409,58 @@ package body Sem is
                   when Iir_Kind_Association_Element_By_Individual =>
                      null;
                   when others =>
-                     Error_Kind
-                       ("sem_generic_port_map_association_chain(1)", El);
+                     Error_Kind ("sem_generic_map_association_chain(1)", El);
                end case;
                El := Get_Chain (El);
             end loop;
          end if;
       end if;
+   end Sem_Generic_Association_Chain;
+
+   --  INTER_PARENT contains ports interfaces;
+   --  ASSOC_PARENT constains ports map aspects.
+   procedure Sem_Port_Association_Chain
+     (Inter_Parent : Iir; Assoc_Parent : Iir)
+   is
+      El : Iir;
+      Actual : Iir;
+      Prefix : Iir;
+      Object : Iir;
+      Match : Boolean;
+      Assoc_Chain : Iir;
+      Miss : Missing_Type;
+      Inter : Iir;
+      Formal : Iir;
+   begin
+      --  Note: CHECK_MATCH argument of sem_subprogram_arguments must be
+      --   true if parent is a component instantiation.
+      case Get_Kind (Assoc_Parent) is
+         when Iir_Kind_Component_Instantiation_Statement =>
+            --  LRM 9.6 Component Instantiation Statement
+            --  Each local generic (or subelement or slice thereof) must be
+            --  associated {VHDL87: exactly}{VHDL93: at most} once.
+            --  ...
+            --  Each local port (or subelement or slice therof) must be
+            --  associated {VHDL87: exactly}{VHDL93: at most} once.
+
+            --  GHDL: for a direct instantiation, follow rules of
+            --  LRM 1.1.1.1 Generic and LRM 1.1.1.2 Ports.
+            if Flags.Vhdl_Std = Vhdl_87
+              or else Get_Kind (Inter_Parent) = Iir_Kind_Entity_Declaration
+            then
+               Miss := Missing_Port;
+            else
+               Miss := Missing_Allowed;
+            end if;
+         when Iir_Kind_Binding_Indication =>
+            --  LRM 5.2.1.2  Generic map and port map aspects
+            Miss := Missing_Allowed;
+         when Iir_Kind_Block_Header =>
+            --  FIXME: it is possible to have port unassociated ?
+            Miss := Missing_Port;
+         when others =>
+            Error_Kind ("sem_port_association_list", Assoc_Parent);
+      end case;
 
       --  The ports
       Assoc_Chain := Get_Port_Map_Aspect_Chain (Assoc_Parent);
@@ -420,7 +468,7 @@ package body Sem is
          return;
       end if;
       Sem_Association_Chain (Get_Port_Chain (Inter_Parent), Assoc_Chain,
-                             True, Miss_Port, Assoc_Parent, Match);
+                             True, Miss, Assoc_Parent, Match);
       Set_Port_Map_Aspect_Chain (Assoc_Parent, Assoc_Chain);
       if not Match then
          return;
@@ -528,6 +576,16 @@ package body Sem is
          end if;
          El := Get_Chain (El);
       end loop;
+   end Sem_Port_Association_Chain;
+
+   --  INTER_PARENT contains generics and ports interfaces;
+   --  ASSOC_PARENT constains generics and ports map aspects.
+   procedure Sem_Generic_Port_Association_Chain
+     (Inter_Parent : Iir; Assoc_Parent : Iir)
+   is
+   begin
+      Sem_Generic_Association_Chain (Inter_Parent, Assoc_Parent);
+      Sem_Port_Association_Chain (Inter_Parent, Assoc_Parent);
    end Sem_Generic_Port_Association_Chain;
 
    --  LRM 1.3  Configuration Declarations.
@@ -2172,6 +2230,7 @@ package body Sem is
    is
       Unit : Iir_Design_Unit;
       Implicit : Implicit_Signal_Declaration_Type;
+      Header : constant Iir := Get_Package_Header (Decl);
    begin
       Unit := Get_Design_Unit (Decl);
       Sem_Scopes.Add_Name (Decl);
@@ -2193,6 +2252,14 @@ package body Sem is
 
       Push_Signals_Declarative_Part (Implicit, Decl);
 
+      if Header /= Null_Iir then
+         Sem_Interface_Chain (Get_Generic_Chain (Header), Interface_Generic);
+         if Get_Generic_Map_Aspect_Chain (Header) /= Null_Iir then
+            --  FIXME: todo
+            raise Internal_Error;
+         end if;
+      end if;
+
       Sem_Declaration_Chain (Decl);
       --  GHDL: subprogram bodies appear in package body.
 
@@ -2257,6 +2324,49 @@ package body Sem is
       Close_Declarative_Region;
    end Sem_Package_Body;
 
+   --  LRM08 4.9  Package Instantiation Declaration
+   procedure Sem_Package_Instantiation_Declaration (Decl : Iir)
+   is
+      Name : Iir;
+      Pkg : Iir;
+   begin
+      Sem_Scopes.Add_Name (Decl);
+      Set_Visible_Flag (Decl, True);
+      Xref_Decl (Decl);
+
+      --  LRM08 4.9
+      --  The uninstantiated package name shall denote an uninstantiated
+      --  package declared in a package declaration.
+      Name := Get_Uninstantiated_Name (Decl);
+      Sem_Name (Name, False);
+      Pkg := Get_Named_Entity (Name);
+      if Get_Kind (Pkg) = Iir_Kind_Design_Unit then
+         Pkg := Get_Library_Unit (Pkg);
+         Set_Named_Entity (Name, Pkg);
+      end if;
+      if Get_Kind (Pkg) /= Iir_Kind_Package_Declaration then
+         Error_Msg_Sem ("name must denote a package declaration", Name);
+
+         --  What could be done ?
+         return;
+      elsif not Is_Uninstantiated_Package (Pkg) then
+         Error_Msg_Sem
+           (Disp_Node (Pkg) & " is not an uninstantiated package", Name);
+
+         --  What could be done ?
+         return;
+      end if;
+
+      Xref_Name (Name);
+
+      --  LRM08 4.9
+      --  The generic map aspect, if present, optionally associates a single
+      --  actual with each formal generic (or member thereof) in the
+      --  corresponding package declaration.  Each formal generic (or member
+      --  thereof) shall be associated at most once.
+      Sem_Generic_Association_Chain (Get_Package_Header (Pkg), Decl);
+   end Sem_Package_Instantiation_Declaration;
+
    --  LRM 10.4  Use Clauses.
    procedure Sem_Use_Clause (Clauses: Iir_Use_Clause)
    is
@@ -2305,11 +2415,20 @@ package body Sem is
          case Get_Kind (Prefix_Name) is
             when Iir_Kind_Library_Declaration =>
                null;
-            when Iir_Kind_Package_Declaration =>
+            when Iir_Kind_Package_Instantiation_Declaration =>
                null;
+            when Iir_Kind_Package_Declaration =>
+               --  LRM08 12.4 Use clauses
+               --  It is an error if the prefix of a selected name in a use
+               --  clause denotes an uninstantiated package.
+               if Is_Uninstantiated_Package (Prefix_Name) then
+                  Error_Msg_Sem
+                    ("use of uninstantiated package is not allowed", Prefix);
+                  return;
+               end if;
             when others =>
-               Error_Msg_Sem ("prefix must designate a package or a library",
-                              Prefix);
+               Error_Msg_Sem
+                 ("prefix must designate a package or a library", Prefix);
                return;
          end case;
 
@@ -2460,6 +2579,8 @@ package body Sem is
             Sem_Package_Body (El);
          when Iir_Kind_Configuration_Declaration =>
             Sem_Configuration_Declaration (El);
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            Sem_Package_Instantiation_Declaration (El);
          when others =>
             Error_Kind ("semantic", El);
       end case;
diff --git a/sem_decls.adb b/sem_decls.adb
index 09042c4..4ad015c 100644
--- a/sem_decls.adb
+++ b/sem_decls.adb
@@ -1900,6 +1900,136 @@ package body Sem_Decls is
       return Res;
    end Sem_Signature;
 
+   --  Create implicit aliases for an alias ALIAS of a type or of a subtype.
+   procedure Add_Aliases_For_Type_Alias (Alias : Iir)
+   is
+      N_Entity : constant Iir := Get_Name (Alias);
+      Def : constant Iir := Get_Base_Type (Get_Type (N_Entity));
+      Type_Decl : constant Iir := Get_Type_Declarator (Def);
+      Last : Iir;
+      El : Iir;
+      Enum_List : Iir_Enumeration_Literal_List;
+
+      --  Append an implicit alias
+      procedure Add_Implicit_Alias (Decl : Iir)
+      is
+         N_Alias : constant Iir_Non_Object_Alias_Declaration :=
+           Create_Iir (Iir_Kind_Non_Object_Alias_Declaration);
+      begin
+         Location_Copy (N_Alias, Alias);
+         Set_Identifier (N_Alias, Get_Identifier (Decl));
+         Set_Name (N_Alias, Decl);
+         Set_Parent (N_Alias, Get_Parent (Alias));
+
+         Sem_Scopes.Add_Name (N_Alias);
+         Set_Visible_Flag (N_Alias, True);
+
+         --  Append in the declaration chain.
+         Set_Chain (N_Alias, Get_Chain (Last));
+         Set_Chain (Last, N_Alias);
+         Last := N_Alias;
+      end Add_Implicit_Alias;
+   begin
+      Last := Alias;
+
+      if Get_Kind (Def) = Iir_Kind_Enumeration_Type_Definition then
+         --  LRM93 4.3.3.2  Non-Object Aliases
+         --  3.  If the name denotes an enumeration type, then one
+         --      implicit alias declaration for each of the
+         --      literals of the type immediatly follows the alias
+         --      declaration for the enumeration type; [...]
+         --
+         --  LRM08 6.6.3 Nonobject aliases
+         --  c)  If the name denotes an enumeration type of a subtype of an
+         --      enumeration type, then one implicit alias declaration for each
+         --      of the litereals of the base type immediately follows the
+         --      alias declaration for the enumeration type; [...]
+         Enum_List := Get_Enumeration_Literal_List (Def);
+         for I in Natural loop
+            El := Get_Nth_Element (Enum_List, I);
+            exit when El = Null_Iir;
+            --  LRM93 4.3.3.2  Non-Object Aliases
+            --      [...] each such implicit declaration has, as its alias
+            --      designator, the simple name or character literal of the
+            --      literal, and has, as its name, a name constructed by taking
+            --      the name of the alias for the enumeration type and
+            --      substituting the simple name or character literal being
+            --      aliased for the simple name of the type.  Each implicit
+            --      alias has a signature that matches the parameter and result
+            --      type profile of the literal being aliased.
+            --
+            --  LRM08 6.6.3 Nonobject aliases
+            --      [...] each such implicit declaration has, as its alias
+            --      designator, the simple name or character literal of the
+            --      literal and has, as its name, a name constructed by taking
+            --      the name of the alias for the enumeration type or subtype
+            --      and substituing the simple name or character literal being
+            --      aliased for the simple name of the type or subtype.  Each
+            --      implicit alias has a signature that matches the parameter
+            --      and result type profile of the literal being aliased.
+            Add_Implicit_Alias (El);
+         end loop;
+      end if;
+
+      --  LRM93 4.3.3.2  Non-Object Aliases
+      --  4.  Alternatively, if the name denotes a physical type
+      --      [...]
+      --  GHDL: this is not possible, since a physical type is
+      --  anonymous (LRM93 is buggy on this point).
+      --
+      --  LRM08 6.6.3 Nonobject aliases
+      --  d)  Alternatively, if the name denotes a subtype of a physical type,
+      --      [...]
+      if Get_Kind (Def) = Iir_Kind_Physical_Type_Definition then
+         --  LRM08 6.3.3 Nonobject aliases
+         --      [...] then one implicit alias declaration for each of the
+         --      units of the base type immediately follows the alias
+         --      declaration for the physical type; each such implicit
+         --      declaration has, as its alias designator, the simple name of
+         --      the unit and has, as its name, a name constructed by taking
+         --      the name of the alias for the subtype of the physical type
+         --      and substituting the simple name of the unit being aliased for
+         --      the simple name of the subtype.
+         El := Get_Unit_Chain (Def);
+         while El /= Null_Iir loop
+            Add_Implicit_Alias (El);
+            El := Get_Chain (El);
+         end loop;
+      end if;
+
+      --  LRM93 4.3.3.2  Non-Object Aliases
+      --  5.  Finally, if the name denotes a type, then implicit
+      --      alias declarations for each predefined operator
+      --      for the type immediatly follow the explicit alias
+      --      declaration for the type, and if present, any
+      --      implicit alias declarations for literals or units
+      --      of the type.
+      --      Each implicit alias has a signature that matches the
+      --      parameter and result type profule of the implicit
+      --      operator being aliased.
+      --
+      --  LRM08 6.6.3 Nonobject aliases
+      --  e)  Finally, if the name denotes a type of a subtype, then implicit
+      --      alias declarations for each predefined operation for the type
+      --      immediately follow the explicit alias declaration for the type or
+      --      subtype and, if present, any implicit alias declarations for
+      --      literals or units of the type.  Each implicit alias has a
+      --      signature that matches the parameter and result type profile of
+      --      the implicit operation being aliased.
+      El := Get_Chain (Type_Decl);
+      while El /= Null_Iir loop
+         case Get_Kind (El) is
+            when Iir_Kind_Implicit_Function_Declaration
+              | Iir_Kind_Implicit_Procedure_Declaration =>
+               exit when Get_Type_Reference (El) /= Type_Decl;
+            when others =>
+               exit;
+         end case;
+         Add_Implicit_Alias (El);
+         El := Get_Chain (El);
+      end loop;
+   end Add_Aliases_For_Type_Alias;
+
    procedure Sem_Non_Object_Alias_Declaration
      (Alias : Iir_Non_Object_Alias_Declaration)
    is
@@ -1924,94 +2054,16 @@ package body Sem_Decls is
                               Alias);
             end if;
          when Iir_Kind_Type_Declaration =>
-            declare
-               Def : Iir;
-               Last : Iir;
-               El : Iir;
-               Enum_List : Iir_Enumeration_Literal_List;
-
-               procedure Add_Implicit_Alias (Decl : Iir)
-               is
-                  N_Alias : constant Iir_Non_Object_Alias_Declaration :=
-                    Create_Iir (Iir_Kind_Non_Object_Alias_Declaration);
-               begin
-                  Location_Copy (N_Alias, Alias);
-                  Set_Identifier (N_Alias, Get_Identifier (Decl));
-                  Set_Name (N_Alias, Decl);
-
-                  Add_Name (El, Get_Identifier (El), False);
-                  Set_Visible_Flag (N_Alias, True);
-
-                  --  Append in the declaration chain.
-                  Set_Chain (N_Alias, Get_Chain (Last));
-                  Set_Chain (Last, N_Alias);
-                  Last := N_Alias;
-               end Add_Implicit_Alias;
-            begin
-               Def := Get_Type (N_Entity);
-               Last := Alias;
-               if Get_Kind (Def) = Iir_Kind_Enumeration_Type_Definition then
-                  --  LRM93 4.3.3.2  Non-Object Aliases
-                  --  3.  If the name denotes an enumeration type, then one
-                  --      implicit alias declaration for each of the
-                  --      literals of the type immediatly follows the alias
-                  --      declaration for the enumeration type; [...]
-                  Enum_List := Get_Enumeration_Literal_List (Def);
-                  for I in Natural loop
-                     El := Get_Nth_Element (Enum_List, I);
-                     exit when El = Null_Iir;
-                     --  LRM93 4.3.3.2  Non-Object Aliases
-                     --      [...] each such implicit declaration has, as
-                     --      its alias designator, the simple name or
-                     --      character literal of the literal, and has,
-                     --      as its name, a name constructed
-                     --      by taking the name of the alias for the
-                     --      enumeration type and substituting the simple
-                     --      name or character literal being aliased for
-                     --      the simple name of the type.
-                     --      Each implicit alias has a signature that
-                     --      matches the parameter and result type profile
-                     --      of the literal being aliased.
-                     Add_Implicit_Alias (El);
-                  end loop;
-               end if;
-
-               --  LRM93 4.3.3.2  Non-Object Aliases
-               --  4.  Alternatively, if the name denotes a physical type
-               --      [...]
-               -- GHDL: this is not possible, since a physical type is
-               -- anonymous (LRM93 is buggy on this point).
-               if Get_Kind (Def) = Iir_Kind_Physical_Type_Definition then
-                  raise Internal_Error;
-               end if;
-
-               --  LRM93 4.3.3.2  Non-Object Aliases
-               --  5.  Finally, if the name denotes a type, then implicit
-               --      alias declarations for each predefined operator
-               --      for the type immediatly follow the explicit alias
-               --      declaration for the type, and if present, any
-               --      implicit alias declarations for literals or units
-               --      of the type.
-               --      Each implicit alias has a signature that matches the
-               --      parameter and result type profule of the implicit
-               --      operator being aliased.
-               El := Get_Chain (N_Entity);
-               while El /= Null_Iir loop
-                  case Get_Kind (El) is
-                     when Iir_Kind_Implicit_Function_Declaration
-                       | Iir_Kind_Implicit_Procedure_Declaration =>
-                        exit when Get_Type_Reference (El) /= N_Entity;
-                     when others =>
-                        exit;
-                  end case;
-                  Add_Implicit_Alias (El);
-                  El := Get_Chain (El);
-               end loop;
-            end;
+            Add_Aliases_For_Type_Alias (Alias);
+         when Iir_Kind_Subtype_Declaration =>
+            --  LRM08 6.6.3 Nonobject aliases
+            --  ... or a subtype ...
+            if Flags.Vhdl_Std >= Vhdl_08 then
+               Add_Aliases_For_Type_Alias (Alias);
+            end if;
          when Iir_Kinds_Object_Declaration =>
             raise Internal_Error;
-         when Iir_Kind_Subtype_Declaration
-           | Iir_Kind_Attribute_Declaration
+         when Iir_Kind_Attribute_Declaration
            | Iir_Kind_Component_Declaration =>
             null;
          when Iir_Kind_Terminal_Declaration =>
diff --git a/sem_expr.adb b/sem_expr.adb
index 0814355..33addfd 100644
--- a/sem_expr.adb
+++ b/sem_expr.adb
@@ -1696,7 +1696,10 @@ package body Sem_Expr is
                raise Internal_Error;
             end if;
 
-            --  If DECL has already been seen, then skip it.
+            --  LRM08 12.3 Visibility
+            --  [...] or all visible declarations denote the same named entity.
+            --
+            --  GHDL: If DECL has already been seen, then skip it.
             if Get_Seen_Flag (Decl) then
                goto Next;
             end if;
diff --git a/sem_scopes.adb b/sem_scopes.adb
index 810c70d..e00ffb8 100644
--- a/sem_scopes.adb
+++ b/sem_scopes.adb
@@ -17,6 +17,7 @@
 --  02111-1307, USA.
 with Ada.Text_IO;
 with GNAT.Table;
+with Flags; use Flags;
 with Name_Table; -- use Name_Table;
 with Errorout; use Errorout;
 with Iirs_Utils;
@@ -446,7 +447,10 @@ package body Sem_Scopes is
       if Current_Inter = No_Name_Interpretation
         or else (Current_Inter = Conflict_Interpretation and not Potentially)
       then
-         -- Very simple: no hide, no overloading.
+         --  Very simple: no hidding, no overloading.
+         --  (current interpretation is Conflict_Interpretation if there is
+         --   only potentially visible declarations that are not made directly
+         --   visible).
          Save_Current_Interpretation;
          Add_New_Interpretation;
          return;
@@ -457,6 +461,7 @@ package body Sem_Scopes is
             --  Yet another conflicting interpretation.
             return;
          end if;
+
          -- Do not re-add a potential decl
          declare
             Inter: Name_Interpretation_Type := Current_Inter;
@@ -470,7 +475,7 @@ package body Sem_Scopes is
          end;
       end if;
 
-      --  LRM §10.3:
+      --  LRM 10.3 Visibility
       --  Each of two declarations is said to be a homograph of the other if
       --  both declarations have the same identifier, operator symbol, or
       --  character literal, and overloading is allowed for at most one
@@ -483,9 +488,10 @@ package body Sem_Scopes is
       Current_Decl := Get_Declaration (Current_Inter);
 
       if Is_Overloadable (Current_Decl) and then Is_Overloadable (Decl) then
-         --  Current_Inter and Decl overloads.
+         --  Current_Inter and Decl overloads (well, they have the same
+         --  designator).
 
-         --  LRM 10.3
+         --  LRM 10.3 Visibility
          --  If overloading is allowed for both declarations, then each of the
          --  two is a homograph of the other if they have the same identifier,
          --  operator symbol or character literal, as well as the same
@@ -494,6 +500,7 @@ package body Sem_Scopes is
          declare
             Homograph : Name_Interpretation_Type;
             Prev_Homograph : Name_Interpretation_Type;
+            Current_Decl_Non_Alias : Iir;
 
             procedure Maybe_Save_And_Add_New_Interpretation is
             begin
@@ -536,6 +543,15 @@ package body Sem_Scopes is
                end if;
             end Get_Hash_Non_Alias;
 
+            --  Return TRUE iff D is an implicit alias of an implicit
+            --  subprogram.
+            function Is_Implicit_Alias (D : Iir) return Boolean is
+            begin
+               return Get_Kind (D) = Iir_Kind_Non_Object_Alias_Declaration
+                 and then Get_Kind (Get_Name (D))
+                 in Iir_Kinds_Implicit_Subprogram_Declaration;
+            end Is_Implicit_Alias;
+
             Decl_Hash : Iir_Int32;
             Hash : Iir_Int32;
          begin
@@ -559,74 +575,126 @@ package body Sem_Scopes is
             if Homograph = No_Name_Interpretation then
                --  Simple case: no homograph.
                Maybe_Save_And_Add_New_Interpretation;
-            else
-               --  There is an homograph.
-               if Potentially then
-                  --  LRM 10.4 Use Clauses
-                  --  1. A potentially visible declaration is not made
-                  --  directly visible if the place considered is within the
-                  --  immediate scope of a homograph of the declaration.
-                  if Is_In_Current_Declarative_Region (Homograph) then
-                     if not Is_Potentially_Visible (Homograph) then
-                        return;
-                     end if;
+               return;
+            end if;
 
-                     --  GHDL: if the homograph is in the same declarative
-                     --  region than DECL, it must be an implicit declaration
-                     --  to be hidden.
-                     --  FIXME: this rule is not in the LRM.
-                     if Get_Parent (Decl) = Get_Parent (Current_Decl) then
-                        --  Note: no need to save previous interpretation!
-                        Add_New_Interpretation;
-                        Hide_Homograph;
+            --  There is an homograph.
+            if Potentially then
+               --  LRM 10.4 Use Clauses
+               --  1. A potentially visible declaration is not made
+               --  directly visible if the place considered is within the
+               --  immediate scope of a homograph of the declaration.
+               if Is_In_Current_Declarative_Region (Homograph) then
+                  if not Is_Potentially_Visible (Homograph) then
+                     return;
+                  end if;
+
+                  --  GHDL: if the homograph is in the same declarative
+                  --  region than DECL, it must be an implicit declaration
+                  --  to be hidden.
+                  --  FIXME: this rule is not in the LRM.
+                  if Get_Parent (Decl) = Get_Parent (Current_Decl) then
+                     if Flags.Vhdl_Std >= Vhdl_08
+                       and then Is_Implicit_Alias (Decl)
+                     then
+                        --  Re-declaration of an implicit subprogram via
+                        --  an implicit alias is simply discarded.
                         return;
                      end if;
 
-                     --  The homograph is potentially visible and was declared
-                     --  in a scope different from the DECL scope.
-                     --  (ie, it was certainly made visible by another use
-                     --   clause).
+                     --  Note: no need to save previous interpretation, as it
+                     --  is in the same declarative region.
                      Add_New_Interpretation;
+                     Hide_Homograph;
                      return;
-                  else
-                     --  The homograph was made visible in an outer declarative
-                     --  region.  Therefore, it must not be hidden.
-                     Maybe_Save_And_Add_New_Interpretation;
                   end if;
+
+                  --  The homograph is potentially visible and was declared
+                  --  in a scope different from the DECL scope.
+                  --  (ie, it was certainly made visible by another use
+                  --   clause).
+                  Add_New_Interpretation;
+                  return;
                else
-                  if not Is_Potentially_Visible (Homograph) then
-                     if Is_In_Current_Declarative_Region (Homograph) then
-                        if Get_Kind (Current_Decl)
-                          /= Iir_Kind_Implicit_Function_Declaration
-                          and then
-                          Get_Kind (Current_Decl)
-                          /= Iir_Kind_Implicit_Procedure_Declaration
-                        then
-                           Error_Msg_Sem
-                             ("redeclaration of " & Disp_Node (Current_Decl)
-                              & " defined at " & Disp_Location (Current_Decl),
-                              Decl);
+                  --  The homograph was made visible in an outer declarative
+                  --  region.  Therefore, it must not be hidden.
+                  Maybe_Save_And_Add_New_Interpretation;
+               end if;
+
+               return;
+
+            else
+               --  Added declaration DECL is made directly visible.
+
+               if not Is_Potentially_Visible (Homograph) then
+                  --  The homograph was also directly visible
+                  if Is_In_Current_Declarative_Region (Homograph) then
+                     --  ... and was declared in the same region
+
+                     --  LRM08 12.3 Visibility
+                     --  Two declarations that occur immediately within
+                     --  the same declarative regions [...] shall not be
+                     --  homograph, unless exactely one of them is the
+                     --  implicit declaration of a predefined operation, or
+                     --  is an implicit alias of such implicit declaration.
+                     --
+                     --  GHDL: FIXME: 'implicit alias'
+
+                     --  LRM08 12.3 Visibility
+                     --  LRM93 10.3 Visibility
+                     --  Each of two declarations is said to be a
+                     --  homograph of the other if and only if both
+                     --  declarations have the same designator, [...]
+                     --
+                     --  LRM08 12.3 Visibility
+                     --  [...] and they denote differrent named entities,
+                     --  and [...]
+                     if Flags.Vhdl_Std >= Vhdl_08 then
+                        if Is_Implicit_Alias (Decl) then
+                           --  Re-declaration of an implicit subprogram via
+                           --  an implicit alias is simply discarded.
+                           --  FIXME: implicit alias.
                            return;
                         end if;
+
+                        Current_Decl_Non_Alias :=
+                          Get_Non_Alias_Declaration (Homograph);
                      else
-                        --  Overload.
-                        null;
+                        Current_Decl_Non_Alias := Current_Decl;
                      end if;
+
+                     if Get_Kind (Current_Decl_Non_Alias)
+                       not in Iir_Kinds_Implicit_Subprogram_Declaration
+                     then
+                        Error_Msg_Sem
+                          ("redeclaration of " & Disp_Node (Current_Decl)
+                             & " defined at " & Disp_Location (Current_Decl),
+                           Decl);
+                        return;
+                     end if;
+
+                     --  FIXME: simply discard DECL if an *implicit* alias
+                     --  of the current declaration?
                   else
-                     --  LRM 10.4 Use Clauses
-                     --  1. A potentially visible declaration is not made
-                     --  directly visible if the place considered is within the
-                     --  immediate scope of a homograph of the declaration.
+                     --  GHDL: hide directly visible declaration declared in
+                     --  an outer region.
                      null;
                   end if;
-                  Maybe_Save_And_Add_New_Interpretation;
+               else
+                  --  LRM 10.4 Use Clauses
+                  --  1. A potentially visible declaration is not made
+                  --  directly visible if the place considered is within the
+                  --  immediate scope of a homograph of the declaration.
 
-                  Hide_Homograph;
-                  return;
+                  --  GHDL: hide the potentially visible declaration.
+                  null;
                end if;
+               Maybe_Save_And_Add_New_Interpretation;
+
+               Hide_Homograph;
+               return;
             end if;
          end;
-         return;
       end if;
 
       -- The current interpretation and the new one are homograph.
@@ -964,7 +1032,11 @@ package body Sem_Scopes is
    procedure Add_Package_Declarations
      (Decl: Iir_Package_Declaration; Potentially : Boolean)
    is
+      Header : constant Iir := Get_Package_Header (Decl);
    begin
+      if Header /= Null_Iir then
+         Add_Declarations (Get_Generic_Chain (Header), Potentially);
+      end if;
       Add_Declarations (Get_Declaration_Chain (Decl), Potentially);
    end Add_Package_Declarations;
 
@@ -1040,6 +1112,15 @@ package body Sem_Scopes is
             Use_Library_All (Name);
          when Iir_Kind_Package_Declaration =>
             Add_Package_Declarations (Name, True);
+         when Iir_Kind_Package_Instantiation_Declaration =>
+            declare
+               Pkg : constant Iir :=
+                 Get_Named_Entity (Get_Uninstantiated_Name (Name));
+            begin
+               if Pkg /= Null_Iir then
+                  Add_Package_Declarations (Pkg, True);
+               end if;
+            end;
          when others =>
             raise Internal_Error;
       end case;