[Ada] Fix a freezing issue

2018-07-31  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* sem.ads (Inside_Preanalysis_Without_Freezing): New global
	counter.
	* sem.adb (Semantics): This subprogram has now the
	responsibility of resetting the counter before analyzing a unit,
	and restoring its previous value before returning.
	* freeze.adb (Freeze_Entity): Do not freeze if we are
	preanalyzing without freezing.
	* sem_res.adb (Preanalyze_And_Resolve): Set & restore
	In_Preanalysis_Without_Freezing.

From-SVN: r263091

gcc/ada/ChangeLog

@@ -1,3 +1,15 @@
+2018-07-31  Javier Miranda  <miranda@adacore.com>
+
+	* sem.ads (Inside_Preanalysis_Without_Freezing): New global
+	counter.
+	* sem.adb (Semantics): This subprogram has now the
+	responsibility of resetting the counter before analyzing a unit,
+	and restoring its previous value before returning.
+	* freeze.adb (Freeze_Entity): Do not freeze if we are
+	preanalyzing without freezing.
+	* sem_res.adb (Preanalyze_And_Resolve): Set & restore
+	In_Preanalysis_Without_Freezing.
+
 2018-07-31  Ed Schonberg  <schonberg@adacore.com>
 
 	* sem_ch4.adb (Traverse_Homonyms): Consider generic actuals that

gcc/ada/freeze.adb

@@ -5280,6 +5280,12 @@ package body Freeze is
          Result := No_List;
          goto Leave;
 
+      --  Do not freeze if we are preanalyzing without freezing
+
+      elsif Inside_Preanalysis_Without_Freezing > 0 then
+         Result := No_List;
+         goto Leave;
+
       elsif Ekind (E) = E_Generic_Package then
          Result := Freeze_Generic_Entities (E);
          goto Leave;

gcc/ada/sem.adb

@@ -1447,9 +1447,18 @@ package body Sem is
       --  unit. All with'ed units are analyzed with config restrictions reset
       --  and we need to restore these saved values at the end.
 
+      Save_Preanalysis_Counter : constant Nat :=
+                                   Inside_Preanalysis_Without_Freezing;
+      --  Saves the preanalysis nesting-level counter; required since we may
+      --  need to analyze a unit as a consequence of the preanalysis of an
+      --  expression without freezing (and the loaded unit must be fully
+      --  analyzed).
+
    --  Start of processing for Semantics
 
    begin
+      Inside_Preanalysis_Without_Freezing := 0;
+
       if Debug_Unit_Walk then
          if Already_Analyzed then
             Write_Str ("(done)");
@@ -1622,6 +1631,8 @@ package body Sem is
             Unit (Comp_Unit),
             Prefix => "<-- ");
       end if;
+
+      Inside_Preanalysis_Without_Freezing := Save_Preanalysis_Counter;
    end Semantics;
 
    --------

gcc/ada/sem.ads

@@ -286,6 +286,11 @@ package Sem is
    --  freezing nodes can modify the status of this flag, any other client
    --  should regard it as read-only.
 
+   Inside_Preanalysis_Without_Freezing : Nat := 0;
+   --  Flag indicating whether we are preanalyzing an expression performing no
+   --  freezing. Non-zero means we are inside (it is actually a level counter
+   --  to deal with nested calls).
+
    Unloaded_Subunits : Boolean := False;
    --  This flag is set True if we have subunits that are not loaded. This
    --  occurs when the main unit is a subunit, and contains lower level

gcc/ada/sem_res.adb

@@ -1671,14 +1671,17 @@ package body Sem_Res is
       T             : Entity_Id;
       With_Freezing : Boolean)
    is
-      Save_Full_Analysis   : constant Boolean := Full_Analysis;
-      Save_Must_Not_Freeze : constant Boolean := Must_Not_Freeze (N);
-
+      Save_Full_Analysis     : constant Boolean := Full_Analysis;
+      Save_Must_Not_Freeze   : constant Boolean := Must_Not_Freeze (N);
+      Save_Preanalysis_Count : constant Nat :=
+                                 Inside_Preanalysis_Without_Freezing;
    begin
       pragma Assert (Nkind (N) in N_Subexpr);
 
       if not With_Freezing then
          Set_Must_Not_Freeze (N);
+         Inside_Preanalysis_Without_Freezing :=
+           Inside_Preanalysis_Without_Freezing + 1;
       end if;
 
       Full_Analysis := False;
@@ -1708,6 +1711,14 @@ package body Sem_Res is
       Expander_Mode_Restore;
       Full_Analysis := Save_Full_Analysis;
       Set_Must_Not_Freeze (N, Save_Must_Not_Freeze);
+
+      if not With_Freezing then
+         Inside_Preanalysis_Without_Freezing :=
+           Inside_Preanalysis_Without_Freezing - 1;
+      end if;
+
+      pragma Assert
+        (Inside_Preanalysis_Without_Freezing = Save_Preanalysis_Count);
    end Preanalyze_And_Resolve;
 
    ----------------------------