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Handle unions differently in std.fmt (#1432)

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* Handle unions differently in std.fmt

Print the active tag's value in tagged unions. Untagged unions considered unsafe to print and treated like a pointer or an array.
This commit is contained in:
tgschultz 2018-08-27 16:25:33 -05:00 committed by Andrew Kelley
parent 009e90f446
commit ecc5464024
1 changed files with 98 additions and 17 deletions
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115
std/fmt/index.zig
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@ -163,26 +163,47 @@ pub fn formatType(
}
break :cf false;
};
if (has_cust_fmt) return value.format(fmt, context, Errors, output);
try output(context, @typeName(T));
if (comptime @typeId(T) == builtin.TypeId.Enum) {
try output(context, ".");
try formatType(@tagName(value), "", context, Errors, output);
return;
switch (comptime @typeId(T)) {
builtin.TypeId.Enum => {
try output(context, ".");
try formatType(@tagName(value), "", context, Errors, output);
return;
},
builtin.TypeId.Struct => {
comptime var field_i = 0;
inline while (field_i < @memberCount(T)) : (field_i += 1) {
if (field_i == 0) {
try output(context, "{ .");
} else {
try output(context, ", .");
}
try output(context, @memberName(T, field_i));
try output(context, " = ");
try formatType(@field(value, @memberName(T, field_i)), "", context, Errors, output);
}
try output(context, " }");
},
builtin.TypeId.Union => {
const info = @typeInfo(T).Union;
if(info.tag_type) |UnionTagType| {
try output(context, "{ .");
try output(context, @tagName(UnionTagType(value)));
try output(context, " = ");
inline for(info.fields) |u_field| {
if(@enumToInt(UnionTagType(value)) == u_field.enum_field.?.value) {
try formatType(@field(value, u_field.name), "", context, Errors, output);
}
}
try output(context, " }");
} else {
try format(context, Errors, output, "@{x}", @ptrToInt(&value));
}
},
else => unreachable,
}
comptime var field_i = 0;
inline while (field_i < @memberCount(T)) : (field_i += 1) {
if (field_i == 0) {
try output(context, "{ .");
} else {
try output(context, ", .");
}
try output(context, @memberName(T, field_i));
try output(context, " = ");
try formatType(@field(value, @memberName(T, field_i)), "", context, Errors, output);
}
try output(context, " }");
return;
},
builtin.TypeId.Pointer => |ptr_info| switch (ptr_info.size) {
@ -1194,6 +1215,66 @@ test "fmt.format" {
try testFmt("point: (10.200,2.220)\n", "point: {}\n", value);
try testFmt("dim: 10.200x2.220\n", "dim: {d}\n", value);
}
//struct format
{
const S = struct {
a: u32,
b: error,
};
const inst = S {
.a = 456,
.b = error.Unused,
};
try testFmt("S{ .a = 456, .b = error.Unused }", "{}", inst);
}
//union format
{
const TU = union(enum)
{
float: f32,
int: u32,
};
const UU = union
{
float: f32,
int: u32,
};
const EU = extern union
{
float: f32,
int: u32,
};
const tu_inst = TU{ .int = 123, };
const uu_inst = UU{ .int = 456, };
const eu_inst = EU{ .float = 321.123, };
try testFmt("TU{ .int = 123 }", "{}", tu_inst);
var buf: [100]u8 = undefined;
const uu_result = try bufPrint(buf[0..], "{}", uu_inst);
debug.assert(mem.eql(u8, uu_result[0..3], "UU@"));
const eu_result = try bufPrint(buf[0..], "{}", eu_inst);
debug.assert(mem.eql(u8, uu_result[0..3], "EU@"));
}
//enum format
{
const E = enum
{
One,
Two,
Three,
};
const inst = E.Two;
try testFmt("E.Two", "{}", inst);
}
}
fn testFmt(expected: []const u8, comptime template: []const u8, args: ...) !void {