diff options
Diffstat (limited to 'gcc/ada/par-ch3.adb')
| -rw-r--r-- | gcc/ada/par-ch3.adb | 60 |
1 files changed, 54 insertions, 6 deletions
diff --git a/gcc/ada/par-ch3.adb b/gcc/ada/par-ch3.adb index 973f643..820cb55 100644 --- a/gcc/ada/par-ch3.adb +++ b/gcc/ada/par-ch3.adb @@ -2057,11 +2057,14 @@ package body Ch3 is -- Error recovery: cannot raise Error_Resync - function P_Range_Or_Subtype_Mark return Node_Id is + function P_Range_Or_Subtype_Mark + (Allow_Simple_Expression : Boolean := False) return Node_Id + is Expr_Node : Node_Id; Range_Node : Node_Id; Save_Loc : Source_Ptr; + -- Start of processing for P_Range_Or_Subtype_Mark begin @@ -2071,7 +2074,8 @@ package body Ch3 is -- Scan out either a simple expression or a range (this accepts more -- than is legal here, but as explained above, we like to allow more - -- with a proper diagnostic. + -- with a proper diagnostic, and in the case of a membership operation + -- where sets are allowed, a simple expression is permissible anyway. Expr_Node := P_Simple_Expression_Or_Range_Attribute; @@ -3555,7 +3559,6 @@ package body Ch3 is begin Choices := New_List; - loop if Token = Tok_Others then Append (New_Node (N_Others_Choice, Token_Ptr), Choices); @@ -3563,6 +3566,8 @@ package body Ch3 is else begin + -- Scan out expression or range attribute + Expr_Node := P_Expression_Or_Range_Attribute; Ignore (Tok_Right_Paren); @@ -3572,9 +3577,13 @@ package body Ch3 is Error_Msg_SP ("label not permitted in this context"); Scan; -- past colon + -- Range attribute + elsif Expr_Form = EF_Range_Attr then Append (Expr_Node, Choices); + -- Explicit range + elsif Token = Tok_Dot_Dot then Check_Simple_Expression (Expr_Node); Choice_Node := New_Node (N_Range, Token_Ptr); @@ -3585,14 +3594,16 @@ package body Ch3 is Set_High_Bound (Choice_Node, Expr_Node); Append (Choice_Node, Choices); + -- Simple name, must be subtype, so range allowed + elsif Expr_Form = EF_Simple_Name then if Token = Tok_Range then Append (P_Subtype_Indication (Expr_Node), Choices); elsif Token in Token_Class_Consk then Error_Msg_SC - ("the only constraint allowed here " & - "is a range constraint"); + ("the only constraint allowed here " & + "is a range constraint"); Discard_Junk_Node (P_Constraint_Opt); Append (Expr_Node, Choices); @@ -3600,8 +3611,45 @@ package body Ch3 is Append (Expr_Node, Choices); end if; + -- Expression + else - Check_Simple_Expression_In_Ada_83 (Expr_Node); + -- If extensions are permitted then the expression must be a + -- simple expression. The resaon for this restriction (i.e. + -- going back to the Ada 83 rule) is to avoid ambiguities + -- when set membership operations are allowed, consider the + -- following: + + -- when A in 1 .. 10 | 12 => + + -- This is ambiguous without parentheses, so we require one + -- of the following two parenthesized forms to disambuguate: + + -- one of the following: + + -- when (A in 1 .. 10 | 12) => + -- when (A in 1 .. 10) | 12 => + + -- We consider it unlikely that reintroducing the Ada 83 + -- restriction will cause an upwards incompatibility issue. + -- Historically the only reason for the change in Ada 95 was + -- for consistency (all cases of Simple_Expression in Ada 83 + -- which could be changed to Expression without causing any + -- ambiguities were changed). + + if Extensions_Allowed and then Expr_Form = EF_Non_Simple then + Error_Msg_N + ("|this expression must be parenthesized!", + Expr_Node); + Error_Msg_N + ("\|since extensions (and set notation) are allowed", + Expr_Node); + + -- In Ada 83 mode, the syntax required a simple expression + else + Check_Simple_Expression_In_Ada_83 (Expr_Node); + end if; + Append (Expr_Node, Choices); end if; |