[PATCH] ada/29015: Do not ICE on incomplete type whose underlying type is known

[PATCH] ada/29015: Do not ICE on incomplete type whose underlying type is known

[Samuel Tardieu]

When an incomplete type is used in an instantiation, GNAT correctly
rejects it if its use is premature. However, if the Underlying_Type is
present, GNAT assumes that the use is not premature and tries to use
the type Full_View unconditionally.

In some cases, the Underlying_Type may be known even if the type is
incomplete. In the following example, compiling incomplete2.adb will
analyze incomplete1.ads. In incomplete2.ads, there is only a "limited
with" on Incomplete1. At G instantiation time, the type Incomplete1.T
has no Full_View but its Underlying_Type is known.

This patch checks the full view instead of the underlying type, giving
the following error message:

% gcc -c -gnatv incomplete2.adb
==============Error messages for source file: incomplete2.ads
     7.    package I1 is new G (Incomplete1.T);
                                           |
        >>> premature use of incomplete type
        >>> instantiation abandoned


instead of a bug box.

Regtested on i686-pc-linux-gnu.

Ok for trunk?

    gcc/ada/
	PR ada/29015
	* sem_ch12.adb (Instantiate_Type): Check whether the full view of
	the type is known instead of the underlying type.

    gcc/testsuite/
	PR ada/29015
	* gnat.dg/incomplete1.ads, gnat.dg/incomplete2.ads,
	gnat.dg/incomplete2.adb: New.
---
 gcc/ada/sem_ch12.adb                  |    2 +-
 gcc/testsuite/gnat.dg/incomplete1.ads |    3 +++
 gcc/testsuite/gnat.dg/incomplete2.adb |    4 ++++
 gcc/testsuite/gnat.dg/incomplete2.ads |    8 ++++++++
 4 files changed, 16 insertions(+), 1 deletions(-)
 create mode 100644 gcc/testsuite/gnat.dg/incomplete1.ads
 create mode 100644 gcc/testsuite/gnat.dg/incomplete2.adb
 create mode 100644 gcc/testsuite/gnat.dg/incomplete2.ads

diff --git a/gcc/ada/sem_ch12.adb b/gcc/ada/sem_ch12.adb
index 00c9f39..b22af91 100644
--- a/gcc/ada/sem_ch12.adb
+++ b/gcc/ada/sem_ch12.adb
@@ -9980,7 +9980,7 @@ package body Sem_Ch12 is
                          Ekind (Root_Type (Act_T)) = E_Incomplete_Type)
          then
             if Is_Class_Wide_Type (Act_T)
-              or else No (Underlying_Type (Act_T))
+              or else No (Full_View (Act_T))
             then
                Error_Msg_N ("premature use of incomplete type", Actual);
                Abandon_Instantiation (Actual);
diff --git a/gcc/testsuite/gnat.dg/incomplete1.ads b/gcc/testsuite/gnat.dg/incomplete1.ads
new file mode 100644
index 0000000..3490033
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/incomplete1.ads
@@ -0,0 +1,3 @@
+package Incomplete1 is
+   type T is null record;
+end Incomplete1;
diff --git a/gcc/testsuite/gnat.dg/incomplete2.adb b/gcc/testsuite/gnat.dg/incomplete2.adb
new file mode 100644
index 0000000..19c8360
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/incomplete2.adb
@@ -0,0 +1,4 @@
+-- { dg-do compile }
+-- { dg-excess-errors "instantiation abandoned" }
+with Incomplete1;
+package body Incomplete2 is end Incomplete2;
diff --git a/gcc/testsuite/gnat.dg/incomplete2.ads b/gcc/testsuite/gnat.dg/incomplete2.ads
new file mode 100644
index 0000000..21f2d2b
--- /dev/null
+++ b/gcc/testsuite/gnat.dg/incomplete2.ads
@@ -0,0 +1,8 @@
+limited with Incomplete1;
+package Incomplete2 is
+   pragma Elaborate_Body;
+   generic
+      type T is private;
+   package G is end G;
+   package I1 is new G (Incomplete1.T); -- { dg-error "premature use" }
+end Incomplete2;
-- 
1.5.4.5

Re: [PATCH] ada/29015: Do not ICE on incomplete type whose underlying type is known

[Arnaud Charlet]

> Ok for trunk?
> 
>     gcc/ada/
> 	PR ada/29015
> 	* sem_ch12.adb (Instantiate_Type): Check whether the full view of
> 	the type is known instead of the underlying type.
> 
>     gcc/testsuite/
> 	PR ada/29015
> 	* gnat.dg/incomplete1.ads, gnat.dg/incomplete2.ads,
> 	gnat.dg/incomplete2.adb: New.

This patch is OK.

Arno