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Bug: zig test results in no output #1103

bheads opened this Issue Jun 12, 2018 · 4 comments


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3 participants

bheads commented Jun 12, 2018

Running: zig test test.zig results in no output. But commenting out the last two lines works as expected:

const std = @import("std");
const mem = std.mem;
const builtin = @import("builtin");
const TypeId = builtin.TypeId;
const TypeInfo = builtin.TypeInfo;

const assert = std.debug.assert;

////////////////////////// Type utils ///////////////////////

pub fn isTypeId(comptime T: var, comptime Tid: TypeId) bool {
    comptime return @typeId(asType(T)) == Tid;

pub fn asType(comptime T: var) type { // T may not be a type, get the type or return T
    comptime return switch(@typeId(@typeOf(T))) {
        TypeId.Type => T,
        else => @typeOf(T),

///////////////////// Function Utils /////////////////////

pub fn isFunction(comptime T: var) bool {
    comptime return isTypeId(T, TypeId.Fn);

///////////////////// Pointer Utils /////////////////////

pub fn isPointer(comptime T: var) bool {    
    comptime return isTypeId(T, TypeId.Pointer);

pub fn pointerOf(comptime T: var) type {
    comptime if (!isPointer(T)) unreachable; // must be a pointer
    comptime return @typeInfo(asType(T)).Pointer.child;

///////////////////// Struct Utils /////////////////////

pub fn isStruct(comptime T: var) bool {    
    comptime return isTypeId(T, TypeId.Struct);

pub fn isStructPtr(comptime T: var) bool {    
    comptime return isPointer(T) and isStruct(pointerOf(T));

// Is there a function with this name, TODO: can this also handle unions?
pub fn structHasFunction(comptime T: var, comptime name: []const u8, comptime FT: type) bool {
    comptime if (!isStruct(T) and !isStructPtr(T)) unreachable;
    comptime if (!isFunction(FT)) unreachable; // T must be a struct and FT must be a function
    comptime const ST = asType(comptime if (isStructPtr(T)) pointerOf(T) else T); // unwrap the struct pointer

    comptime const defs = @typeInfo(ST).Struct.defs;
    comptime for(defs) |def| {           
        if ( == TypeInfo.Definition.Data.Fn and == FT and mem.eql(u8, name, return true;
    comptime return false;

test "structHasFunction" {
    assert(structHasFunction(struct { fn foo() void {}}, "foo", fn() void));
    assert(structHasFunction(struct { fn foo(a: f64, b: ?i32) void {} }, "foo", fn(f64, ?i32) void));
    assert(!structHasFunction(struct { fn foo() void {}}, "foo2", fn() void));

    // BUG: these last two lines causes the test to not report (not sure if its crashing)
    std.debug.warn("{}\n", structHasFunction(mem.Allocator, "alloc", fn(*mem.Allocator, var, var) var));
    assert(structHasFunction(mem.Allocator, "alloc", fn(*mem.Allocator, var, var) var));

@andrewrk andrewrk added this to the 0.3.0 milestone Jun 12, 2018

@andrewrk andrewrk added the bug label Jun 12, 2018


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mlouielu commented Jun 13, 2018

I get segmentation fault when the last two line appears, on master commit.


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mlouielu commented Jun 13, 2018

@andrewrk does this related to #758?

Since when I change the FT type to others (not var), then it will not crash.


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andrewrk commented Sep 3, 2018

@mlouielu yes you are correct, this is the same main issue as #758. I will add a similar compile error for this.

@andrewrk andrewrk closed this in a11e73b Sep 3, 2018


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andrewrk commented Sep 3, 2018

now this code gives:

/home/andy/dev/zig/build/test.zig:74:70: error: TODO implement inferred return types
    std.debug.warn("{}\n", structHasFunction(mem.Allocator, "alloc", fn (*mem.Allocator, var, var) var));

#447 is currently scheduled for 0.4.0.

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