From cf5327b89ab610649c5faab78ea7907bb74b103c Mon Sep 17 00:00:00 2001
From: Harald Anlauf <anlauf@gmx.de>
Date: Sun, 11 Dec 2022 23:24:03 +0100
Subject: [PATCH] Fortran: improve checking of assumed-size array spec
 [PR102180]

gcc/fortran/ChangeLog:

	PR fortran/102180
	* array.cc (match_array_element_spec): Add check for bad
	assumed-implied-spec.
	(gfc_match_array_spec): Reorder logic so that the first bad array
	element spec may trigger an error.

gcc/testsuite/ChangeLog:

	PR fortran/102180
	* gfortran.dg/pr102180.f90: New test.
---
 gcc/fortran/array.cc                   | 19 ++++++++++++++++---
 gcc/testsuite/gfortran.dg/pr102180.f90 | 19 +++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/pr102180.f90

diff --git a/gcc/fortran/array.cc b/gcc/fortran/array.cc
index bbdb5b392fc..10d9e0c5354 100644
--- a/gcc/fortran/array.cc
+++ b/gcc/fortran/array.cc
@@ -489,7 +489,20 @@ match_array_element_spec (gfc_array_spec *as)
     }
 
   if (gfc_match_char (':') == MATCH_YES)
-    return AS_DEFERRED;
+    {
+      locus old_loc = gfc_current_locus;
+      if (gfc_match_char ('*') == MATCH_YES)
+	{
+	  /* F2018:R821: "assumed-implied-spec  is  [ lower-bound : ] *".  */
+	  gfc_error ("A lower bound must precede colon in "
+		     "assumed-size array specification at %L", &old_loc);
+	  return AS_UNKNOWN;
+	}
+      else
+	{
+	  return AS_DEFERRED;
+	}
+    }
 
   m = gfc_match_expr (upper);
   if (m == MATCH_NO)
@@ -591,6 +604,8 @@ gfc_match_array_spec (gfc_array_spec **asp, bool match_dim, bool match_codim)
     {
       as->rank++;
       current_type = match_array_element_spec (as);
+      if (current_type == AS_UNKNOWN)
+	goto cleanup;
 
       /* Note that current_type == AS_ASSUMED_SIZE for both assumed-size
 	 and implied-shape specifications.  If the rank is at least 2, we can
@@ -600,8 +615,6 @@ gfc_match_array_spec (gfc_array_spec **asp, bool match_dim, bool match_codim)
 
       if (as->rank == 1)
 	{
-	  if (current_type == AS_UNKNOWN)
-	    goto cleanup;
 	  as->type = current_type;
 	}
       else
diff --git a/gcc/testsuite/gfortran.dg/pr102180.f90 b/gcc/testsuite/gfortran.dg/pr102180.f90
new file mode 100644
index 00000000000..cbf3e7299e7
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr102180.f90
@@ -0,0 +1,19 @@
+! { dg-do compile }
+! { dg-options "-fcoarray=lib" }
+! PR fortran/102180 - Improve checking of assumed size array spec
+
+subroutine s(x,y)
+  real :: x(0:*) ! legal
+  real :: y[0:*] ! legal
+end
+
+subroutine t(x,y)
+  real :: x(:*) ! { dg-error "A lower bound must precede colon" }
+  real :: y[:*] ! { dg-error "A lower bound must precede colon" }
+end
+
+subroutine u(x,y,z)
+  real :: x(2,*)
+  real :: y(2,2:*)
+  real :: z(2,:*) ! { dg-error "A lower bound must precede colon" }
+end
-- 
2.35.3