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Sema: implement comptime error return traces
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@Vexu @andrewrk
Vexu authored and andrewrk committed Jan 23, 2024
1 parent 9e684e8 commit eeec34c
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Showing 4 changed files with 147 additions and 22 deletions.
12 changes: 12 additions & 0 deletions src/Module.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3479,6 +3479,9 @@ pub fn semaFile(mod: *Module, file: *File) SemaError!void {
var comptime_mutable_decls = std.ArrayList(Decl.Index).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -3492,6 +3495,7 @@ pub fn semaFile(mod: *Module, file: *File) SemaError!void {
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down Expand Up @@ -3600,6 +3604,9 @@ fn semaDecl(mod: *Module, decl_index: Decl.Index) !bool {
var comptime_mutable_decls = std.ArrayList(Decl.Index).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -3613,6 +3620,7 @@ fn semaDecl(mod: *Module, decl_index: Decl.Index) !bool {
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
.builtin_type_target_index = builtin_type_target_index,
};
defer sema.deinit();
Expand Down Expand Up @@ -4451,6 +4459,9 @@ pub fn analyzeFnBody(mod: *Module, func_index: InternPool.Index, arena: Allocato
var comptime_mutable_decls = std.ArrayList(Decl.Index).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

// In the case of a generic function instance, this is the type of the
// instance, which has comptime parameters elided. In other words, it is
// the runtime-known parameters only, not to be confused with the
Expand All @@ -4473,6 +4484,7 @@ pub fn analyzeFnBody(mod: *Module, func_index: InternPool.Index, arena: Allocato
.owner_func_index = func_index,
.branch_quota = @max(func.branchQuota(ip).*, Sema.default_branch_quota),
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down
135 changes: 113 additions & 22 deletions src/Sema.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,7 @@ func_index: InternPool.Index,
func_is_naked: bool,
/// Used to restore the error return trace when returning a non-error from a function.
error_return_trace_index_on_fn_entry: Air.Inst.Ref = .none,
comptime_err_ret_trace: *std.ArrayList(Module.SrcLoc),
/// When semantic analysis needs to know the return type of the function whose body
/// is being analyzed, this `Type` should be used instead of going through `func`.
/// This will correctly handle the case of a comptime/inline function call of a
Expand Down Expand Up @@ -1569,7 +1570,22 @@ fn analyzeBodyInner(
const inst_data = datas[@intFromEnum(inst)].pl_node;
const extra = sema.code.extraData(Zir.Inst.Block, inst_data.payload_index);
const inline_body = sema.code.bodySlice(extra.end, extra.data.body_len);
const break_data = (try sema.analyzeBodyBreak(block, inline_body)) orelse

// Create a temporary child block so that this loop is properly
// labeled for any .restore_err_ret_index instructions
var child_block = block.makeSubBlock();

var label: Block.Label = .{
.zir_block = inst,
.merges = undefined,
};
child_block.label = &label;

// Write these instructions directly into the parent block
child_block.instructions = block.instructions;
defer block.instructions = child_block.instructions;

const break_data = (try sema.analyzeBodyBreak(&child_block, inline_body)) orelse
break always_noreturn;
if (inst == break_data.block_inst) {
break :blk try sema.resolveInst(break_data.operand);
Expand All @@ -1585,13 +1601,22 @@ fn analyzeBodyInner(
const inst_data = datas[@intFromEnum(inst)].pl_node;
const extra = sema.code.extraData(Zir.Inst.Block, inst_data.payload_index);
const inline_body = sema.code.bodySlice(extra.end, extra.data.body_len);
// If this block contains a function prototype, we need to reset the
// current list of parameters and restore it later.
// Note: this probably needs to be resolved in a more general manner.
const prev_params = block.params;
block.params = .{};
defer block.params = prev_params;
const break_data = (try sema.analyzeBodyBreak(block, inline_body)) orelse

// Create a temporary child block so that this block is properly
// labeled for any .restore_err_ret_index instructions
var child_block = block.makeSubBlock();

var label: Block.Label = .{
.zir_block = inst,
.merges = undefined,
};
child_block.label = &label;

// Write these instructions directly into the parent block
child_block.instructions = block.instructions;
defer block.instructions = child_block.instructions;

const break_data = (try sema.analyzeBodyBreak(&child_block, inline_body)) orelse
break always_noreturn;
if (inst == break_data.block_inst) {
break :blk try sema.resolveInst(break_data.operand);
Expand Down Expand Up @@ -2379,6 +2404,25 @@ fn typeSupportsFieldAccess(mod: *const Module, ty: Type, field_name: InternPool.
}
}

fn failWithComptimeErrorRetTrace(
sema: *Sema,
block: *Block,
src: LazySrcLoc,
name: InternPool.NullTerminatedString,
) CompileError {
const mod = sema.mod;
const msg = msg: {
const msg = try sema.errMsg(block, src, "caught unexpected error '{}'", .{name.fmt(&mod.intern_pool)});
errdefer msg.destroy(sema.gpa);

for (sema.comptime_err_ret_trace.items) |src_loc| {
try mod.errNoteNonLazy(src_loc, msg, "error returned here", .{});
}
break :msg msg;
};
return sema.failWithOwnedErrorMsg(block, msg);
}

/// We don't return a pointer to the new error note because the pointer
/// becomes invalid when you add another one.
fn errNote(
Expand Down Expand Up @@ -6534,10 +6578,12 @@ pub fn analyzeSaveErrRetIndex(sema: *Sema, block: *Block) SemaError!Air.Inst.Ref
const gpa = sema.gpa;
const src = sema.src;

if (!block.ownerModule().error_tracing) return .none;
if (block.is_comptime or block.is_typeof) {
const index_val = try mod.intValue_u64(Type.usize, sema.comptime_err_ret_trace.items.len);
return Air.internedToRef(index_val.toIntern());
}

if (block.is_comptime)
return .none;
if (!block.ownerModule().error_tracing) return .none;

const stack_trace_ty = sema.getBuiltinType("StackTrace") catch |err| switch (err) {
error.NeededSourceLocation, error.GenericPoison, error.ComptimeReturn, error.ComptimeBreak => unreachable,
Expand Down Expand Up @@ -7498,6 +7544,14 @@ fn analyzeCall(
try sema.ensureResultUsed(block, sema.fn_ret_ty, call_src);
}

if (is_comptime_call or block.is_typeof) {
// Save the error trace as our first action in the function
// to match the behavior of runtime function calls.
const error_return_trace_index = try sema.analyzeSaveErrRetIndex(&child_block);
sema.error_return_trace_index_on_fn_entry = error_return_trace_index;
child_block.error_return_trace_index = error_return_trace_index;
}

const result = result: {
sema.analyzeBody(&child_block, fn_info.body) catch |err| switch (err) {
error.ComptimeReturn => break :result inlining.comptime_result,
Expand Down Expand Up @@ -7858,6 +7912,7 @@ fn instantiateGenericCall(
.branch_quota = sema.branch_quota,
.branch_count = sema.branch_count,
.comptime_mutable_decls = sema.comptime_mutable_decls,
.comptime_err_ret_trace = sema.comptime_err_ret_trace,
};
defer child_sema.deinit();

Expand Down Expand Up @@ -8783,7 +8838,7 @@ fn analyzeErrUnionPayload(
const payload_ty = err_union_ty.errorUnionPayload(mod);
if (try sema.resolveDefinedValue(block, operand_src, operand)) |val| {
if (val.getErrorName(mod).unwrap()) |name| {
return sema.fail(block, src, "caught unexpected error '{}'", .{name.fmt(&mod.intern_pool)});
return sema.failWithComptimeErrorRetTrace(block, src, name);
}
return Air.internedToRef(mod.intern_pool.indexToKey(val.toIntern()).error_union.val.payload);
}
Expand Down Expand Up @@ -8861,7 +8916,7 @@ fn analyzeErrUnionPayloadPtr(
}
if (try sema.pointerDeref(block, src, ptr_val, operand_ty)) |val| {
if (val.getErrorName(mod).unwrap()) |name| {
return sema.fail(block, src, "caught unexpected error '{}'", .{name.fmt(&mod.intern_pool)});
return sema.failWithComptimeErrorRetTrace(block, src, name);
}
return Air.internedToRef((try mod.intern(.{ .ptr = .{
.ty = operand_pointer_ty.toIntern(),
Expand Down Expand Up @@ -13437,7 +13492,7 @@ fn maybeErrorUnwrapComptime(sema: *Sema, block: *Block, body: []const Zir.Inst.I

if (try sema.resolveDefinedValue(block, src, operand)) |val| {
if (val.getErrorName(sema.mod).unwrap()) |name| {
return sema.fail(block, src, "caught unexpected error '{}'", .{name.fmt(&sema.mod.intern_pool)});
return sema.failWithComptimeErrorRetTrace(block, src, name);
}
}
}
Expand Down Expand Up @@ -19227,15 +19282,9 @@ fn zirRestoreErrRetIndex(sema: *Sema, start_block: *Block, inst: Zir.Inst.Index)
const inst_data = sema.code.instructions.items(.data)[@intFromEnum(inst)].restore_err_ret_index;
const src = sema.src; // TODO

// This is only relevant at runtime.
if (start_block.is_comptime or start_block.is_typeof) return;

const mod = sema.mod;
const ip = &mod.intern_pool;

if (!ip.funcAnalysis(sema.owner_func_index).calls_or_awaits_errorable_fn) return;
if (!start_block.ownerModule().error_tracing) return;

const tracy = trace(@src());
defer tracy.end();

Expand Down Expand Up @@ -19263,9 +19312,29 @@ fn zirRestoreErrRetIndex(sema: *Sema, start_block: *Block, inst: Zir.Inst.Index)
return; // No need to restore
};

const operand = try sema.resolveInstAllowNone(inst_data.operand);

if (start_block.is_comptime or start_block.is_typeof) {
const is_non_error = if (operand != .none) blk: {
const is_non_error_inst = try sema.analyzeIsNonErr(start_block, src, operand);
const cond_val = try sema.resolveDefinedValue(start_block, src, is_non_error_inst);
break :blk cond_val.?.toBool();
} else true; // no operand means pop unconditionally

if (is_non_error) return;

const saved_index_val = try sema.resolveDefinedValue(start_block, src, saved_index);
const saved_index_int = saved_index_val.?.toUnsignedInt(mod);
assert(saved_index_int <= sema.comptime_err_ret_trace.items.len);
sema.comptime_err_ret_trace.items.len = @intCast(saved_index_int);
return;
}

if (!ip.funcAnalysis(sema.owner_func_index).calls_or_awaits_errorable_fn) return;
if (!start_block.ownerModule().error_tracing) return;

assert(saved_index != .none); // The .error_return_trace_index field was dropped somewhere

const operand = try sema.resolveInstAllowNone(inst_data.operand);
return sema.popErrorReturnTrace(start_block, src, operand, saved_index);
}

Expand Down Expand Up @@ -19319,10 +19388,16 @@ fn analyzeRet(

if (block.inlining) |inlining| {
if (block.is_comptime) {
_ = try sema.resolveConstValue(block, src, operand, .{
const ret_val = try sema.resolveConstValue(block, src, operand, .{
.needed_comptime_reason = "value being returned at comptime must be comptime-known",
});
inlining.comptime_result = operand;

if (sema.fn_ret_ty.isError(mod) and ret_val.getErrorName(mod) != .none) {
const src_decl = mod.declPtr(block.src_decl);
const src_loc = src.toSrcLoc(src_decl, mod);
try sema.comptime_err_ret_trace.append(src_loc);
}
return error.ComptimeReturn;
}
// We are inlining a function call; rewrite the `ret` as a `break`.
Expand Down Expand Up @@ -35467,6 +35542,9 @@ fn semaBackingIntType(mod: *Module, struct_type: InternPool.Key.StructType) Comp
var comptime_mutable_decls = std.ArrayList(InternPool.DeclIndex).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(Module.SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -35480,6 +35558,7 @@ fn semaBackingIntType(mod: *Module, struct_type: InternPool.Key.StructType) Comp
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down Expand Up @@ -36289,6 +36368,9 @@ fn semaStructFields(
var comptime_mutable_decls = std.ArrayList(InternPool.DeclIndex).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(Module.SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -36302,6 +36384,7 @@ fn semaStructFields(
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down Expand Up @@ -36543,6 +36626,9 @@ fn semaStructFieldInits(
var comptime_mutable_decls = std.ArrayList(InternPool.DeclIndex).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(Module.SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -36556,6 +36642,7 @@ fn semaStructFieldInits(
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down Expand Up @@ -36727,6 +36814,9 @@ fn semaUnionFields(mod: *Module, arena: Allocator, union_type: InternPool.Key.Un
var comptime_mutable_decls = std.ArrayList(InternPool.DeclIndex).init(gpa);
defer comptime_mutable_decls.deinit();

var comptime_err_ret_trace = std.ArrayList(Module.SrcLoc).init(gpa);
defer comptime_err_ret_trace.deinit();

var sema: Sema = .{
.mod = mod,
.gpa = gpa,
Expand All @@ -36740,6 +36830,7 @@ fn semaUnionFields(mod: *Module, arena: Allocator, union_type: InternPool.Key.Un
.fn_ret_ty_ies = null,
.owner_func_index = .none,
.comptime_mutable_decls = &comptime_mutable_decls,
.comptime_err_ret_trace = &comptime_err_ret_trace,
};
defer sema.deinit();

Expand Down
17 changes: 17 additions & 0 deletions test/cases/compile_errors/comptime_err_ret_trace.zig
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
fn inner() !void {
return error.SomethingBadHappened;
}

fn outer() !void {
return inner();
}

comptime {
outer() catch unreachable;
}

// error
//
// :10:19: error: caught unexpected error 'SomethingBadHappened'
// :2:18: note: error returned here
// :6:5: note: error returned here
5 changes: 5 additions & 0 deletions test/cases/compile_errors/error_in_comptime_call_in_container_level_initializer.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,4 +19,9 @@ pub export fn entry() void {
// target=native
//
// :9:48: error: caught unexpected error 'InvalidVersion'
// :?:?: note: error returned here
// :?:?: note: error returned here
// :?:?: note: error returned here
// :?:?: note: error returned here
// :?:?: note: error returned here
// :12:37: note: called from here

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