remove error to/from int casting syntax; add @errorToInt/@intToError

See #1061

test/cases/cast.zig

@@ -140,8 +140,8 @@ test "explicit cast from integer to error type" {
     comptime testCastIntToErr(error.ItBroke);
 }
 fn testCastIntToErr(err: error) void {
-    const x = usize(err);
-    const y = error(x);
+    const x = @errorToInt(err);
+    const y = @intToError(x);
     assert(error.ItBroke == y);
 }
 

test/cases/error.zig

@@ -31,8 +31,8 @@ test "@errorName" {
 }
 
 test "error values" {
-    const a = i32(error.err1);
-    const b = i32(error.err2);
+    const a = @errorToInt(error.err1);
+    const b = @errorToInt(error.err2);
     assert(a != b);
 }
 
@@ -147,14 +147,14 @@ test "syntax: optional operator in front of error union operator" {
 }
 
 test "comptime err to int of error set with only 1 possible value" {
-    testErrToIntWithOnePossibleValue(error.A, u32(error.A));
-    comptime testErrToIntWithOnePossibleValue(error.A, u32(error.A));
+    testErrToIntWithOnePossibleValue(error.A, @errorToInt(error.A));
+    comptime testErrToIntWithOnePossibleValue(error.A, @errorToInt(error.A));
 }
 fn testErrToIntWithOnePossibleValue(
     x: error{A},
     comptime value: u32,
 ) void {
-    if (u32(x) != value) {
+    if (@errorToInt(x) != value) {
         @compileError("bad");
     }
 }

test/cases/type_info.zig

@@ -130,7 +130,7 @@ fn testErrorSet() void {
     assert(TypeId(error_set_info) == TypeId.ErrorSet);
     assert(error_set_info.ErrorSet.errors.len == 3);
     assert(mem.eql(u8, error_set_info.ErrorSet.errors[0].name, "First"));
-    assert(error_set_info.ErrorSet.errors[2].value == usize(TestErrorSet.Third));
+    assert(error_set_info.ErrorSet.errors[2].value == @errorToInt(TestErrorSet.Third));
 
     const error_union_info = @typeInfo(TestErrorSet!usize);
     assert(TypeId(error_union_info) == TypeId.ErrorUnion);

test/compile_errors.zig

@@ -467,25 +467,34 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
 
     cases.add(
         "int to err global invalid number",
-        \\const Set1 = error{A, B};
+        \\const Set1 = error{
+        \\    A,
+        \\    B,
+        \\};
         \\comptime {
-        \\    var x: usize = 3;
-        \\    var y = error(x);
+        \\    var x: u16 = 3;
+        \\    var y = @intToError(x);
         \\}
     ,
-        ".tmp_source.zig:4:18: error: integer value 3 represents no error",
+        ".tmp_source.zig:7:13: error: integer value 3 represents no error",
     );
 
     cases.add(
         "int to err non global invalid number",
-        \\const Set1 = error{A, B};
-        \\const Set2 = error{A, C};
+        \\const Set1 = error{
+        \\    A,
+        \\    B,
+        \\};
+        \\const Set2 = error{
+        \\    A,
+        \\    C,
+        \\};
         \\comptime {
-        \\    var x = usize(Set1.B);
-        \\    var y = Set2(x);
+        \\    var x = @errorToInt(Set1.B);
+        \\    var y = @errSetCast(Set2, @intToError(x));
         \\}
     ,
-        ".tmp_source.zig:5:17: error: integer value 2 represents no error in 'Set2'",
+        ".tmp_source.zig:11:13: error: error.B not a member of error set 'Set2'",
     );
 
     cases.add(
@@ -2612,17 +2621,6 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         ".tmp_source.zig:2:21: error: expected pointer, found 'usize'",
     );
 
-    cases.add(
-        "too many error values to cast to small integer",
-        \\const Error = error { A, B, C, D, E, F, G, H };
-        \\fn foo(e: Error) u2 {
-        \\    return u2(e);
-        \\}
-        \\export fn entry() usize { return @sizeOf(@typeOf(foo)); }
-    ,
-        ".tmp_source.zig:3:14: error: too many error values to fit in 'u2'",
-    );
-
     cases.add(
         "asm at compile time",
         \\comptime {

test/runtime_safety.zig

@@ -175,7 +175,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
         \\    if (x.len == 0) return error.Whatever;
         \\}
         \\fn widenSlice(slice: []align(1) const u8) []align(1) const i32 {
-        \\    return ([]align(1) const i32)(slice);
+        \\    return @bytesToSlice(i32, slice);
         \\}
     );
 
@@ -227,12 +227,12 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
         \\pub fn main() void {
         \\    _ = bar(9999);
         \\}
-        \\fn bar(x: u32) error {
-        \\    return error(x);
+        \\fn bar(x: u16) error {
+        \\    return @intToError(x);
         \\}
     );
 
-    cases.addRuntimeSafety("cast integer to non-global error set and no match",
+    cases.addRuntimeSafety("@errSetCast error not present in destination",
         \\pub fn panic(message: []const u8, stack_trace: ?*@import("builtin").StackTrace) noreturn {
         \\    @import("std").os.exit(126);
         \\}
@@ -242,7 +242,7 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
         \\    _ = foo(Set1.B);
         \\}
         \\fn foo(set1: Set1) Set2 {
-        \\    return Set2(set1);
+        \\    return @errSetCast(Set2, set1);
         \\}
     );
 
@@ -252,12 +252,12 @@ pub fn addCases(cases: *tests.CompareOutputContext) void {
         \\}
         \\pub fn main() !void {
         \\    var array align(4) = []u32{0x11111111, 0x11111111};
-        \\    const bytes = ([]u8)(array[0..]);
+        \\    const bytes = @sliceToBytes(array[0..]);
         \\    if (foo(bytes) != 0x11111111) return error.Wrong;
         \\}
         \\fn foo(bytes: []u8) u32 {
         \\    const slice4 = bytes[1..5];
-        \\    const int_slice = ([]u32)(@alignCast(4, slice4));
+        \\    const int_slice = @bytesToSlice(u32, @alignCast(4, slice4));
         \\    return int_slice[0];
         \\}
     );