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carbon-lang/toolchain/check/testdata/let/import.carbon
T
Jon Ross-Perkins f8c8861e5f Change ImportRef to a triple state: Unloaded, Loaded, Used (#3831)
This doesn't significantly change logic, although I'm trying to add the
location to used state.

The issue I'm trying to address is how to identify a declaration as
"allowed to be redeclared". Consider:

```
library "a" api;
extern fn F();
```
```
library "b" api;
extern fn F();
```
```
library "c" api;
import library "a";
import library "b";
var x: auto = F();
fn F();
```

What currently happens is:

1. On import of "a", `F` becomes ImportRefUnused
2. On import of "b", `F` becomes ImportRefUsed in order to merge.
3. In "c", the call `F()` doesn't change the state.
4. In "c", the declaration `fn F();` needs some breadcrumb to understand
whether "F" has been referenced, as in step (3) here.

What I want to happen is:

1. On import of "a", `F` becomes ImportRefUnloaded
2. On import of "b", `F` becomes ImportRefLoaded in order to merge.
3. In "c", the call `F()` causes `F` to become ImportRefUsed
4. In "c", the declaration `fn F();` detects that `F` is already
ImportRefUsed, and can use the associated `used_id` for a diagnostic
about why redeclaring is invalid.

Note this PR isn't implementing (4). I'm focused on the refactoring to
add a new ImportRef state here.
2024-04-02 17:20:09 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// AUTOUPDATE
// --- implicit.carbon
package Implicit api;
let a:! bool = true;
// --- implicit.impl.carbon
package Implicit impl;
let b:! bool = a;
// CHECK:STDOUT: --- implicit.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %.1: bool = bool_literal true [template]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: package: <namespace> = namespace [template] {}
// CHECK:STDOUT: %.loc4: bool = bool_literal true [template = constants.%.1]
// CHECK:STDOUT: %a: bool = bind_symbolic_name a, %.loc4 [symbolic]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: --- implicit.impl.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: package: <namespace> = namespace [template] {
// CHECK:STDOUT: .a = %import_ref
// CHECK:STDOUT: }
// CHECK:STDOUT: %import_ref: bool = import_ref ir1, inst+1, loc_10 [symbolic = <unexpected instref inst+3>]
// CHECK:STDOUT: %a.ref: bool = name_ref a, %import_ref [symbolic = <unexpected instref inst+3>]
// CHECK:STDOUT: %b: bool = bind_symbolic_name b, %a.ref [symbolic]
// CHECK:STDOUT: }
// CHECK:STDOUT: