Fortran: Fix ICE caused by missing error for untyped symbol [PR103258]

The bit on a symbol to mark that it had already been diagnosed as
lacking a type was getting set even when the error was suppressed or
discarded, specifically when doing early resolution on a character
length expression to see if it can be constant-folded.  Explicitly
suppress errors before doing that, then check whether they are
suppressed before setting the bit.

2022-01-04  Sandra Loosemore  <sandra@codesourcery.com>

	PR fortran/103258

	gcc/fortran/
	* decl.c (gfc_match_char_spec): Suppress errors around call
	to gfc_reduce_init_expr.
	* error.c (gfc_query_suppress_errors): New.
	* gfortran.h (gfc_query_suppress_errors): Declare.
	* symbol.c (gfc_set_default_type): Check gfc_query_suppress_errors.

	gcc/testsuite/
	* gfortran.dg/pr103258.f90: New.

gcc/fortran/decl.c

@@ -3609,7 +3609,9 @@ done:
 	  gfc_current_ns = gfc_get_namespace (NULL, 0);
 
 	  e = gfc_copy_expr (len);
+	  gfc_push_suppress_errors ();
 	  gfc_reduce_init_expr (e);
+	  gfc_pop_suppress_errors ();
 	  if (e->expr_type == EXPR_CONSTANT)
 	    {
 	      gfc_replace_expr (len, e);

gcc/fortran/error.c

@@ -83,6 +83,15 @@ gfc_pop_suppress_errors (void)
 }
 
 
+/* Query whether errors are suppressed.  */
+
+bool
+gfc_query_suppress_errors (void)
+{
+  return suppress_errors > 0;
+}
+
+
 /* Determine terminal width (for trimming source lines in output).  */
 
 static int

gcc/fortran/gfortran.h

@@ -1083,6 +1083,7 @@ typedef struct
 
 void gfc_push_suppress_errors (void);
 void gfc_pop_suppress_errors (void);
+bool gfc_query_suppress_errors (void);
 
 
 /* Character length structures hold the expression that gives the

gcc/fortran/symbol.c

@@ -299,7 +299,7 @@ gfc_set_default_type (gfc_symbol *sym, int error_flag, gfc_namespace *ns)
 
   if (ts->type == BT_UNKNOWN)
     {
-      if (error_flag && !sym->attr.untyped)
+      if (error_flag && !sym->attr.untyped && !gfc_query_suppress_errors ())
 	{
 	  const char *guessed = lookup_symbol_fuzzy (sym->name, sym);
 	  if (guessed)

gcc/testsuite/gfortran.dg/pr103258.f90

@@ -0,0 +1,14 @@
+! { dg-do compile}
+! { dg-additional-options "-Wno-pedantic" }
+!
+! Test from PR103258.  This used to ICE due to incorrectly marking the
+! no-implicit-type error for n and m in the character length expression
+! as already diagnosed during early resolution, when in fact errors are
+! ignored in that parsing context.  We now expect the errors to be diagnosed
+! at the point of the first use of each symbol.
+
+subroutine s(n) ! { dg-error "Symbol 'n' .*has no IMPLICIT type" }
+implicit none
+character(n+m) :: c ! { dg-error "Symbol 'm' .*has no IMPLICIT type" }
+entry e(m)
+end