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0fe3fd01dd
The compiler actually doesn't need any functional changes for this: Sema does reification based on the tag indices of `std.builtin.Type` already! So, no zig1.wasm update is necessary. This change is necessary to disallow name clashes between fields and decls on a type, which is a prerequisite of #9938.
37 lines
1.1 KiB
Zig
37 lines
1.1 KiB
Zig
const std = @import("std");
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const expect = std.testing.expect;
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const expectError = std.testing.expectError;
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fn isFieldOptional(comptime T: type, field_index: usize) !bool {
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const fields = @typeInfo(T).@"struct".fields;
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return switch (field_index) {
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// This prong is analyzed twice with `idx` being a
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// comptime-known value each time.
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inline 0, 1 => |idx| @typeInfo(fields[idx].type) == .optional,
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else => return error.IndexOutOfBounds,
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};
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}
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const Struct1 = struct { a: u32, b: ?u32 };
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test "using @typeInfo with runtime values" {
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var index: usize = 0;
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try expect(!try isFieldOptional(Struct1, index));
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index += 1;
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try expect(try isFieldOptional(Struct1, index));
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index += 1;
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try expectError(error.IndexOutOfBounds, isFieldOptional(Struct1, index));
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}
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// Calls to `isFieldOptional` on `Struct1` get unrolled to an equivalent
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// of this function:
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fn isFieldOptionalUnrolled(field_index: usize) !bool {
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return switch (field_index) {
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0 => false,
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1 => true,
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else => return error.IndexOutOfBounds,
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};
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}
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// test
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