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Add an interface for initialization of vars without an explicit initializer (#6934)

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When a `var` is not explicitly given an initializer, initialize it in
one of two ways:

* If its type implements the new interface `Core.Default`, call
`Core.Default.Op` to initialize it.
* Otherwise, if its type implements `UnformedInit`, leave it in an
unformed state. For now, this is always an uninitialized state, but that
will change in the future.
* If neither of those apply, the `var` declaration is ill-formed.

This is a step towards implementing leads decision #6739 and proposals
#257 and #5913.

Assisted-by: Gemini 3.1 Pro via Antigravity

---------

Co-authored-by: Geoff Romer <gromer@google.com>
This commit is contained in:
Richard Smith
2026-03-19 23:46:06 +00:00
committed by GitHub
co-authored by Geoff Romer
parent fd2d210c63
commit ce50f181f1
146 changed files with 5226 additions and 3535 deletions
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toolchain/check/testdata/tuple/tuple_pattern.carbon
Vendored
+22 -10
View File
@@ -15,10 +15,10 @@
library "[[@TEST_NAME]]";
fn F() {
fn F(v: ({}, {})) {
//@dump-sem-ir-begin
let (unused x: {}, unused y: {}) = ({}, {});
var (unused a: {}, unused b: {});
var (unused a: {}, unused b: {}) = v;
var (unused c: {}, unused d: {}) = ({}, {});
//@dump-sem-ir-end
}
@@ -102,18 +102,18 @@ let (a: {}, b: {}) = ({}, {}, {});
// CHECK:STDOUT: --- basic.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %empty_tuple.type: type = tuple_type () [concrete]
// CHECK:STDOUT: %empty_struct_type: type = struct_type {} [concrete]
// CHECK:STDOUT: %empty_struct: %empty_struct_type = struct_value () [concrete]
// CHECK:STDOUT: %pattern_type.a96: type = pattern_type %empty_struct_type [concrete]
// CHECK:STDOUT: %tuple.type.b6b: type = tuple_type (%empty_struct_type, %empty_struct_type) [concrete]
// CHECK:STDOUT: %pattern_type.de4: type = pattern_type %tuple.type.b6b [concrete]
// CHECK:STDOUT: %tuple: %tuple.type.b6b = tuple_value (%empty_struct, %empty_struct) [concrete]
// CHECK:STDOUT: %empty_tuple.type: type = tuple_type () [concrete]
// CHECK:STDOUT: %pattern_type.de4: type = pattern_type %tuple.type.b6b [concrete]
// CHECK:STDOUT: %pattern_type.a96: type = pattern_type %empty_struct_type [concrete]
// CHECK:STDOUT: %Destroy.Op.type: type = fn_type @Destroy.Op [concrete]
// CHECK:STDOUT: %Destroy.Op: %Destroy.Op.type = struct_value () [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @F() {
// CHECK:STDOUT: fn @F(%v.param: %tuple.type.b6b) {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %x.patt: %pattern_type.a96 = value_binding_pattern x [concrete]
@@ -144,18 +144,30 @@ let (a: {}, b: {}) = ({}, {}, {});
// CHECK:STDOUT: %.var_patt.loc7: %pattern_type.de4 = var_pattern %.loc7_34 [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT: %.var.loc7: ref %tuple.type.b6b = var %.var_patt.loc7
// CHECK:STDOUT: %tuple.elem0.loc7: ref %empty_struct_type = tuple_access %.var.loc7, element0
// CHECK:STDOUT: %tuple.elem1.loc7: ref %empty_struct_type = tuple_access %.var.loc7, element1
// CHECK:STDOUT: %v.ref: %tuple.type.b6b = name_ref v, %v
// CHECK:STDOUT: %tuple.elem0.loc7_38.1: %empty_struct_type = tuple_access %v.ref, element0
// CHECK:STDOUT: %tuple.elem0.loc7_38.2: ref %empty_struct_type = tuple_access %.var.loc7, element0
// CHECK:STDOUT: %.loc7_38.1: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
// CHECK:STDOUT: %.loc7_38.2: init %empty_struct_type = converted %tuple.elem0.loc7_38.1, %.loc7_38.1 [concrete = constants.%empty_struct]
// CHECK:STDOUT: %tuple.elem1.loc7_38.1: %empty_struct_type = tuple_access %v.ref, element1
// CHECK:STDOUT: %tuple.elem1.loc7_38.2: ref %empty_struct_type = tuple_access %.var.loc7, element1
// CHECK:STDOUT: %.loc7_38.3: init %empty_struct_type = struct_init () [concrete = constants.%empty_struct]
// CHECK:STDOUT: %.loc7_38.4: init %empty_struct_type = converted %tuple.elem1.loc7_38.1, %.loc7_38.3 [concrete = constants.%empty_struct]
// CHECK:STDOUT: %.loc7_38.5: init %tuple.type.b6b to %.var.loc7 = tuple_init (%.loc7_38.2, %.loc7_38.4) [concrete = constants.%tuple]
// CHECK:STDOUT: %.loc7_3: init %tuple.type.b6b = converted %v.ref, %.loc7_38.5 [concrete = constants.%tuple]
// CHECK:STDOUT: assign %.var.loc7, %.loc7_3
// CHECK:STDOUT: %tuple.elem0.loc7_3: ref %empty_struct_type = tuple_access %.var.loc7, element0
// CHECK:STDOUT: %tuple.elem1.loc7_3: ref %empty_struct_type = tuple_access %.var.loc7, element1
// CHECK:STDOUT: %.loc7_19.1: type = splice_block %.loc7_19.3 [concrete = constants.%empty_struct_type] {
// CHECK:STDOUT: %.loc7_19.2: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
// CHECK:STDOUT: %.loc7_19.3: type = converted %.loc7_19.2, constants.%empty_struct_type [concrete = constants.%empty_struct_type]
// CHECK:STDOUT: }
// CHECK:STDOUT: %a: ref %empty_struct_type = ref_binding a, %tuple.elem0.loc7
// CHECK:STDOUT: %a: ref %empty_struct_type = ref_binding a, %tuple.elem0.loc7_3
// CHECK:STDOUT: %.loc7_33.1: type = splice_block %.loc7_33.3 [concrete = constants.%empty_struct_type] {
// CHECK:STDOUT: %.loc7_33.2: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
// CHECK:STDOUT: %.loc7_33.3: type = converted %.loc7_33.2, constants.%empty_struct_type [concrete = constants.%empty_struct_type]
// CHECK:STDOUT: }
// CHECK:STDOUT: %b: ref %empty_struct_type = ref_binding b, %tuple.elem1.loc7
// CHECK:STDOUT: %b: ref %empty_struct_type = ref_binding b, %tuple.elem1.loc7_3
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %c.patt: %pattern_type.a96 = ref_binding_pattern c [concrete]
// CHECK:STDOUT: %d.patt: %pattern_type.a96 = ref_binding_pattern d [concrete]