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Sema: further enhance explanation of why expr is evaluated at comptime

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This commit is contained in:
Veikka Tuominen 2022-10-27 19:31:45 +03:00
parent c389f8800b
commit c3b85e4e2f
6 changed files with 181 additions and 73 deletions
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185
src/Sema.zig
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@ -151,6 +151,8 @@ pub const Block = struct {
runtime_index: Value.RuntimeIndex = .zero,
inline_block: Zir.Inst.Index = 0,
comptime_reason: ?*const ComptimeReason = null,
// TODO is_comptime and comptime_reason should probably be merged together.
is_comptime: bool,
is_typeof: bool = false,
is_coerce_result_ptr: bool = false,
@ -173,6 +175,49 @@ pub const Block = struct {
/// Value for switch_capture in an inline case
inline_case_capture: Air.Inst.Ref = .none,
const ComptimeReason = union(enum) {
c_import: struct {
block: *Block,
src: LazySrcLoc,
},
comptime_ret_ty: struct {
block: *Block,
func: Air.Inst.Ref,
func_src: LazySrcLoc,
return_ty: Type,
},
fn explain(cr: ComptimeReason, sema: *Sema, msg: ?*Module.ErrorMsg) !void {
const parent = msg orelse return;
const prefix = "expression is evaluated at comptime because ";
switch (cr) {
.c_import => |ci| {
try sema.errNote(ci.block, ci.src, parent, prefix ++ "it is inside a @cImport", .{});
},
.comptime_ret_ty => |rt| {
const src_loc = if (try sema.funcDeclSrc(rt.block, rt.func_src, rt.func)) |capture| blk: {
var src_loc = capture;
src_loc.lazy = .{ .node_offset_fn_type_ret_ty = 0 };
break :blk src_loc;
} else blk: {
const src_decl = sema.mod.declPtr(rt.block.src_decl);
break :blk rt.func_src.toSrcLoc(src_decl);
};
if (rt.return_ty.tag() == .generic_poison) {
return sema.mod.errNoteNonLazy(src_loc, parent, prefix ++ "the generic function was instantiated with a comptime-only return type", .{});
}
try sema.mod.errNoteNonLazy(
src_loc,
parent,
prefix ++ "the function returns a comptime-only type '{}'",
.{rt.return_ty.fmt(sema.mod)},
);
try sema.explainWhyTypeIsComptime(rt.block, rt.func_src, parent, src_loc, rt.return_ty);
},
}
}
};
const Param = struct {
/// `noreturn` means `anytype`.
ty: Type,
@ -224,6 +269,7 @@ pub const Block = struct {
.label = null,
.inlining = parent.inlining,
.is_comptime = parent.is_comptime,
.comptime_reason = parent.comptime_reason,
.is_typeof = parent.is_typeof,
.runtime_cond = parent.runtime_cond,
.runtime_loop = parent.runtime_loop,
@ -1420,7 +1466,10 @@ fn analyzeBodyInner(
const extra = sema.code.extraData(Zir.Inst.CondBr, inst_data.payload_index);
const then_body = sema.code.extra[extra.end..][0..extra.data.then_body_len];
const else_body = sema.code.extra[extra.end + then_body.len ..][0..extra.data.else_body_len];
const cond = try sema.resolveInstConst(block, cond_src, extra.data.condition, "condition in comptime branch must be comptime-known");
const cond = sema.resolveInstConst(block, cond_src, extra.data.condition, "condition in comptime branch must be comptime-known") catch |err| {
if (err == error.AnalysisFail and block.comptime_reason != null) try block.comptime_reason.?.explain(sema, sema.err);
return err;
};
const inline_body = if (cond.val.toBool()) then_body else else_body;
try sema.maybeErrorUnwrapCondbr(block, inline_body, extra.data.condition, cond_src);
@ -1438,7 +1487,10 @@ fn analyzeBodyInner(
const extra = sema.code.extraData(Zir.Inst.CondBr, inst_data.payload_index);
const then_body = sema.code.extra[extra.end..][0..extra.data.then_body_len];
const else_body = sema.code.extra[extra.end + then_body.len ..][0..extra.data.else_body_len];
const cond = try sema.resolveInstConst(block, cond_src, extra.data.condition, "condition in comptime branch must be comptime-known");
const cond = sema.resolveInstConst(block, cond_src, extra.data.condition, "condition in comptime branch must be comptime-known") catch |err| {
if (err == error.AnalysisFail and block.comptime_reason != null) try block.comptime_reason.?.explain(sema, sema.err);
return err;
};
const inline_body = if (cond.val.toBool()) then_body else else_body;
const old_runtime_index = block.runtime_index;
defer block.runtime_index = old_runtime_index;
@ -1460,7 +1512,10 @@ fn analyzeBodyInner(
const err_union = try sema.resolveInst(extra.data.operand);
const is_non_err = try sema.analyzeIsNonErrComptimeOnly(block, operand_src, err_union);
assert(is_non_err != .none);
const is_non_err_tv = try sema.resolveInstConst(block, operand_src, is_non_err, "try operand inside comptime block must be comptime-known");
const is_non_err_tv = sema.resolveInstConst(block, operand_src, is_non_err, "try operand inside comptime block must be comptime-known") catch |err| {
if (err == error.AnalysisFail and block.comptime_reason != null) try block.comptime_reason.?.explain(sema, sema.err);
return err;
};
if (is_non_err_tv.val.toBool()) {
const err_union_ty = sema.typeOf(err_union);
break :blk try sema.analyzeErrUnionPayload(block, src, err_union_ty, err_union, operand_src, false);
@ -1516,7 +1571,10 @@ fn analyzeBodyInner(
const err_union = try sema.analyzeLoad(block, src, operand, operand_src);
const is_non_err = try sema.analyzeIsNonErrComptimeOnly(block, operand_src, err_union);
assert(is_non_err != .none);
const is_non_err_tv = try sema.resolveInstConst(block, operand_src, is_non_err, "try operand inside comptime block must be comptime-known");
const is_non_err_tv = sema.resolveInstConst(block, operand_src, is_non_err, "try operand inside comptime block must be comptime-known") catch |err| {
if (err == error.AnalysisFail and block.comptime_reason != null) try block.comptime_reason.?.explain(sema, sema.err);
return err;
};
if (is_non_err_tv.val.toBool()) {
break :blk try sema.analyzeErrUnionPayloadPtr(block, src, operand, false, false);
}
@ -1675,8 +1733,8 @@ pub fn setupErrorReturnTrace(sema: *Sema, block: *Block, last_arg_index: usize)
return;
}
assert(!block.is_comptime);
var err_trace_block = block.makeSubBlock();
err_trace_block.is_comptime = false;
defer err_trace_block.instructions.deinit(sema.gpa);
const src: LazySrcLoc = .unneeded;
@ -4944,6 +5002,10 @@ fn zirCImport(sema: *Sema, parent_block: *Block, inst: Zir.Inst.Index) CompileEr
var c_import_buf = std.ArrayList(u8).init(sema.gpa);
defer c_import_buf.deinit();
var comptime_reason = .{ .c_import = .{
.block = parent_block,
.src = src,
} };
var child_block: Block = .{
.parent = parent_block,
.sema = sema,
@ -4952,7 +5014,8 @@ fn zirCImport(sema: *Sema, parent_block: *Block, inst: Zir.Inst.Index) CompileEr
.wip_capture_scope = parent_block.wip_capture_scope,
.instructions = .{},
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.is_comptime = true,
.comptime_reason = &comptime_reason,
.c_import_buf = &c_import_buf,
.runtime_cond = parent_block.runtime_cond,
.runtime_loop = parent_block.runtime_loop,
@ -5053,6 +5116,7 @@ fn zirBlock(sema: *Sema, parent_block: *Block, inst: Zir.Inst.Index) CompileErro
.label = &label,
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.comptime_reason = parent_block.comptime_reason,
.is_typeof = parent_block.is_typeof,
.want_safety = parent_block.want_safety,
.float_mode = parent_block.float_mode,
@ -5926,6 +5990,7 @@ fn zirCall(
defer block.is_comptime = parent_comptime;
if (arg_index < fn_params_len and func_ty_info.comptime_params[arg_index]) {
block.is_comptime = true;
// TODO set comptime_reason
}
const param_ty_inst = try sema.addType(param_ty);
@ -6056,37 +6121,6 @@ const GenericCallAdapter = struct {
}
};
fn addComptimeReturnTypeNote(
sema: *Sema,
block: *Block,
func: Air.Inst.Ref,
func_src: LazySrcLoc,
return_ty: Type,
parent: *Module.ErrorMsg,
requires_comptime: bool,
) !void {
if (!requires_comptime) return;
const src_loc = if (try sema.funcDeclSrc(block, func_src, func)) |capture| blk: {
var src_loc = capture;
src_loc.lazy = .{ .node_offset_fn_type_ret_ty = 0 };
break :blk src_loc;
} else blk: {
const src_decl = sema.mod.declPtr(block.src_decl);
break :blk func_src.toSrcLoc(src_decl);
};
if (return_ty.tag() == .generic_poison) {
return sema.mod.errNoteNonLazy(src_loc, parent, "generic function is instantiated with a comptime-only return type", .{});
}
try sema.mod.errNoteNonLazy(
src_loc,
parent,
"function is being called at comptime because it returns a comptime-only type '{}'",
.{return_ty.fmt(sema.mod)},
);
try sema.explainWhyTypeIsComptime(block, func_src, parent, src_loc, return_ty);
}
fn analyzeCall(
sema: *Sema,
block: *Block,
@ -6177,11 +6211,21 @@ fn analyzeCall(
var is_generic_call = func_ty_info.is_generic;
var is_comptime_call = block.is_comptime or modifier == .compile_time;
var comptime_only_ret_ty = false;
var comptime_reason_buf: Block.ComptimeReason = undefined;
var comptime_reason: ?*const Block.ComptimeReason = null;
if (!is_comptime_call) {
if (sema.typeRequiresComptime(func_ty_info.return_type)) |ct| {
is_comptime_call = ct;
comptime_only_ret_ty = ct;
if (ct) {
// stage1 can't handle doing this directly
comptime_reason_buf = .{ .comptime_ret_ty = .{
.block = block,
.func = func,
.func_src = func_src,
.return_ty = func_ty_info.return_type,
} };
comptime_reason = &comptime_reason_buf;
}
} else |err| switch (err) {
error.GenericPoison => is_generic_call = true,
else => |e| return e,
@ -6210,7 +6254,14 @@ fn analyzeCall(
error.ComptimeReturn => {
is_inline_call = true;
is_comptime_call = true;
comptime_only_ret_ty = true;
// stage1 can't handle doing this directly
comptime_reason_buf = .{ .comptime_ret_ty = .{
.block = block,
.func = func,
.func_src = func_src,
.return_ty = func_ty_info.return_type,
} };
comptime_reason = &comptime_reason_buf;
},
else => |e| return e,
}
@ -6222,9 +6273,7 @@ fn analyzeCall(
const result: Air.Inst.Ref = if (is_inline_call) res: {
const func_val = sema.resolveConstValue(block, func_src, func, "function being called at comptime must be comptime-known") catch |err| {
if (err == error.AnalysisFail and sema.err != null) {
try sema.addComptimeReturnTypeNote(block, func, func_src, func_ty_info.return_type, sema.err.?, comptime_only_ret_ty);
}
if (err == error.AnalysisFail and comptime_reason != null) try comptime_reason.?.explain(sema, sema.err);
return err;
};
const module_fn = switch (func_val.tag()) {
@ -6292,6 +6341,7 @@ fn analyzeCall(
.label = null,
.inlining = &inlining,
.is_comptime = is_comptime_call,
.comptime_reason = comptime_reason,
.error_return_trace_index = block.error_return_trace_index,
};
@ -6344,11 +6394,6 @@ fn analyzeCall(
is_comptime_call,
&should_memoize,
memoized_call_key,
// last 4 arguments are only used when reporting errors
undefined,
undefined,
undefined,
undefined,
) catch |err| switch (err) {
error.NeededSourceLocation => {
_ = sema.inst_map.remove(inst);
@ -6364,10 +6409,6 @@ fn analyzeCall(
is_comptime_call,
&should_memoize,
memoized_call_key,
func,
func_src,
func_ty_info.return_type,
comptime_only_ret_ty,
);
return error.AnalysisFail;
},
@ -6604,10 +6645,6 @@ fn analyzeInlineCallArg(
is_comptime_call: bool,
should_memoize: *bool,
memoized_call_key: Module.MemoizedCall.Key,
func: Air.Inst.Ref,
func_src: LazySrcLoc,
ret_ty: Type,
comptime_only_ret_ty: bool,
) !void {
const zir_tags = sema.code.instructions.items(.tag);
switch (zir_tags[inst]) {
@ -6624,9 +6661,7 @@ fn analyzeInlineCallArg(
const uncasted_arg = uncasted_args[arg_i.*];
if (try sema.typeRequiresComptime(param_ty)) {
_ = sema.resolveConstMaybeUndefVal(arg_block, arg_src, uncasted_arg, "argument to parameter with comptime-only type must be comptime-known") catch |err| {
if (err == error.AnalysisFail and sema.err != null) {
try sema.addComptimeReturnTypeNote(arg_block, func, func_src, ret_ty, sema.err.?, comptime_only_ret_ty);
}
if (err == error.AnalysisFail and param_block.comptime_reason != null) try param_block.comptime_reason.?.explain(sema, sema.err);
return err;
};
}
@ -6635,9 +6670,7 @@ fn analyzeInlineCallArg(
if (is_comptime_call) {
try sema.inst_map.putNoClobber(sema.gpa, inst, casted_arg);
const arg_val = sema.resolveConstMaybeUndefVal(arg_block, arg_src, casted_arg, "argument to function being called at comptime must be comptime-known") catch |err| {
if (err == error.AnalysisFail and sema.err != null) {
try sema.addComptimeReturnTypeNote(arg_block, func, func_src, ret_ty, sema.err.?, comptime_only_ret_ty);
}
if (err == error.AnalysisFail and param_block.comptime_reason != null) try param_block.comptime_reason.?.explain(sema, sema.err);
return err;
};
switch (arg_val.tag()) {
@ -6679,9 +6712,7 @@ fn analyzeInlineCallArg(
if (is_comptime_call) {
try sema.inst_map.putNoClobber(sema.gpa, inst, uncasted_arg);
const arg_val = sema.resolveConstMaybeUndefVal(arg_block, arg_src, uncasted_arg, "argument to function being called at comptime must be comptime-known") catch |err| {
if (err == error.AnalysisFail and sema.err != null) {
try sema.addComptimeReturnTypeNote(arg_block, func, func_src, ret_ty, sema.err.?, comptime_only_ret_ty);
}
if (err == error.AnalysisFail and param_block.comptime_reason != null) try param_block.comptime_reason.?.explain(sema, sema.err);
return err;
};
switch (arg_val.tag()) {
@ -10223,6 +10254,7 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
.label = &label,
.inlining = block.inlining,
.is_comptime = block.is_comptime,
.comptime_reason = block.comptime_reason,
.is_typeof = block.is_typeof,
.switch_else_err_ty = else_error_ty,
.runtime_cond = block.runtime_cond,
@ -10333,7 +10365,13 @@ fn zirSwitchBlock(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError
return sema.resolveBlockBody(block, src, &child_block, special.body, inst, merges);
}
try sema.requireRuntimeBlock(block, src, operand_src);
if (child_block.is_comptime) {
_ = sema.resolveConstValue(&child_block, operand_src, operand, "condition in comptime switch must be comptime-known") catch |err| {
if (err == error.AnalysisFail and child_block.comptime_reason != null) try child_block.comptime_reason.?.explain(sema, sema.err);
return err;
};
unreachable;
}
const estimated_cases_extra = (scalar_cases_len + multi_cases_len) *
@typeInfo(Air.SwitchBr.Case).Struct.fields.len + 2;
@ -21469,6 +21507,9 @@ fn requireRuntimeBlock(sema: *Sema, block: *Block, src: LazySrcLoc, runtime_src:
if (runtime_src) |some| {
try sema.errNote(block, some, msg, "operation is runtime due to this operand", .{});
}
if (block.comptime_reason) |some| {
try some.explain(sema, msg);
}
break :msg msg;
};
return sema.failWithOwnedErrorMsg(msg);
@ -21940,6 +21981,7 @@ fn addSafetyCheck(
panic_id: PanicId,
) !void {
const gpa = sema.gpa;
assert(!parent_block.is_comptime);
var fail_block: Block = .{
.parent = parent_block,
@ -21949,7 +21991,7 @@ fn addSafetyCheck(
.wip_capture_scope = parent_block.wip_capture_scope,
.instructions = .{},
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.is_comptime = false,
};
defer fail_block.instructions.deinit(gpa);
@ -22061,6 +22103,7 @@ fn panicUnwrapError(
unwrap_err_tag: Air.Inst.Tag,
is_non_err_tag: Air.Inst.Tag,
) !void {
assert(!parent_block.is_comptime);
const ok = try parent_block.addUnOp(is_non_err_tag, operand);
const gpa = sema.gpa;
@ -22072,7 +22115,7 @@ fn panicUnwrapError(
.wip_capture_scope = parent_block.wip_capture_scope,
.instructions = .{},
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.is_comptime = false,
};
defer fail_block.instructions.deinit(gpa);
@ -22104,6 +22147,7 @@ fn panicIndexOutOfBounds(
len: Air.Inst.Ref,
cmp_op: Air.Inst.Tag,
) !void {
assert(!parent_block.is_comptime);
const ok = try parent_block.addBinOp(cmp_op, index, len);
const gpa = sema.gpa;
@ -22115,7 +22159,7 @@ fn panicIndexOutOfBounds(
.wip_capture_scope = parent_block.wip_capture_scope,
.instructions = .{},
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.is_comptime = false,
};
defer fail_block.instructions.deinit(gpa);
@ -22146,6 +22190,7 @@ fn panicSentinelMismatch(
ptr: Air.Inst.Ref,
sentinel_index: Air.Inst.Ref,
) !void {
assert(!parent_block.is_comptime);
const expected_sentinel_val = maybe_sentinel orelse return;
const expected_sentinel = try sema.addConstant(sentinel_ty, expected_sentinel_val);
@ -22186,7 +22231,7 @@ fn panicSentinelMismatch(
.wip_capture_scope = parent_block.wip_capture_scope,
.instructions = .{},
.inlining = parent_block.inlining,
.is_comptime = parent_block.is_comptime,
.is_comptime = false,
};
defer fail_block.instructions.deinit(gpa);

48
test/cases/compile_errors/condition_comptime_reason_explained.zig Normal file
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@ -0,0 +1,48 @@
const S = struct {
fnPtr: fn () void,
};
fn bar() void {}
fn baz() void {}
var runtime: bool = true;
fn ifExpr() S {
if (runtime) {
return .{
.fnPtr = bar,
};
} else {
return .{
.fnPtr = baz,
};
}
}
pub export fn entry1() void {
_ = ifExpr();
}
fn switchExpr() S {
switch (runtime) {
true => return .{
.fnPtr = bar,
},
false => return .{
.fnPtr = baz,
},
}
}
pub export fn entry2() void {
_ = switchExpr();
}
// error
// backend=stage2
// target=native
//
// :8:9: error: unable to resolve comptime value
// :8:9: note: condition in comptime branch must be comptime-known
// :7:13: note: expression is evaluated at comptime because the function returns a comptime-only type 'tmp.S'
// :2:12: note: struct requires comptime because of this field
// :2:12: note: use '*const fn() void' for a function pointer type
// :19:15: note: called from here
// :22:13: error: unable to resolve comptime value
// :22:13: note: condition in comptime switch must be comptime-known
// :21:17: note: expression is evaluated at comptime because the function returns a comptime-only type 'tmp.S'
// :32:19: note: called from here

2
test/cases/compile_errors/explain_why_fn_is_called_at_comptime.zig
View File

@ -18,6 +18,6 @@ pub export fn entry() void {
//
// :12:13: error: unable to resolve comptime value
// :12:13: note: argument to function being called at comptime must be comptime-known
// :7:25: note: function is being called at comptime because it returns a comptime-only type 'tmp.S'
// :7:25: note: expression is evaluated at comptime because the function returns a comptime-only type 'tmp.S'
// :2:12: note: struct requires comptime because of this field
// :2:12: note: use '*const fn() void' for a function pointer type

2
test/cases/compile_errors/explain_why_generic_fn_is_called_at_comptime.zig
View File

@ -19,4 +19,4 @@ pub export fn entry() void {
//
// :14:13: error: unable to resolve comptime value
// :14:13: note: argument to function being called at comptime must be comptime-known
// :9:38: note: generic function is instantiated with a comptime-only return type
// :9:38: note: expression is evaluated at comptime because the generic function was instantiated with a comptime-only return type

15
test/cases/compile_errors/unable_to_evaluate_expr_inside_cimport.zig Normal file
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@ -0,0 +1,15 @@
const c = @cImport({
_ = 1 + foo;
});
extern var foo: i32;
export fn entry() void {
_ = c;
}
// error
// backend=llvm
// target=native
//
// :2:11: error: unable to evaluate comptime expression
// :2:13: note: operation is runtime due to this operand
// :1:11: note: expression is evaluated at comptime because it is inside a @cImport

2
test/compile_errors.zig
View File

@ -204,7 +204,7 @@ pub fn addCases(ctx: *TestContext) !void {
, &[_][]const u8{
":3:12: error: unable to resolve comptime value",
":3:12: note: argument to function being called at comptime must be comptime-known",
":2:55: note: generic function is instantiated with a comptime-only return type",
":2:55: note: expression is evaluated at comptime because the generic function was instantiated with a comptime-only return type",
});
}