fix comptime @tagName crashing sometimes

closes #1118

src/analyze.cpp

@@ -3728,6 +3728,7 @@ TypeUnionField *find_union_field_by_tag(TypeTableEntry *type_entry, const BigInt
 }
 
 TypeEnumField *find_enum_field_by_tag(TypeTableEntry *enum_type, const BigInt *tag) {
+    assert(enum_type->data.enumeration.zero_bits_known);
     for (uint32_t i = 0; i < enum_type->data.enumeration.src_field_count; i += 1) {
         TypeEnumField *field = &enum_type->data.enumeration.fields[i];
         if (bigint_cmp(&field->value, tag) == CmpEQ) {

src/ir.cpp

@@ -16053,6 +16053,9 @@ static TypeTableEntry *ir_analyze_instruction_enum_tag_name(IrAnalyze *ira, IrIn
     assert(target->value.type->id == TypeTableEntryIdEnum);
 
     if (instr_is_comptime(target)) {
+        type_ensure_zero_bits_known(ira->codegen, target->value.type);
+        if (type_is_invalid(target->value.type))
+            return ira->codegen->builtin_types.entry_invalid;
         TypeEnumField *field = find_enum_field_by_tag(target->value.type, &target->value.data.x_bigint);
         ConstExprValue *array_val = create_const_str_lit(ira->codegen, field->name);
         ConstExprValue *out_val = ir_build_const_from(ira, &instruction->base);

test/cases/eval.zig

@@ -637,3 +637,8 @@ test "call method with comptime pass-by-non-copying-value self parameter" {
     var b = s.b();
     assert(b == 2);
 }
+
+test "@tagName of @typeId" {
+    const str = @tagName(@typeId(u8));
+    assert(std.mem.eql(u8, str, "Int"));
+}

test/cases/widening.zig

@@ -19,8 +19,9 @@ test "implicit unsigned integer to signed integer" {
 }
 
 test "float widening" {
-    var a: f32 = 12.34;
-    var b: f64 = a;
-    var c: f128 = b;
-    assert(c == a);
+    var a: f16 = 12.34;
+    var b: f32 = a;
+    var c: f64 = b;
+    var d: f128 = c;
+    assert(d == a);
 }