Add syntax for package and library (#792)

Doesn't add much logic, only takes advantage of parser structure for the ordering enforcement.

Note import_nonexistent tests should probably fail, but writing import tests needs a chain of functionality, and I figured I'd just start adding some to validate the syntax (not adding existent imports because that'd require multi-file structure).

executable_semantics/testdata/assignment_copy1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that assignment performs a copy and does not create an alias.
 
 fn main() -> i32 {

executable_semantics/testdata/assignment_copy2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that assignment performs a copy and does not create an alias.
 
 fn main() -> i32 {

executable_semantics/testdata/block1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var x: i32 = 0;
   {

executable_semantics/testdata/block2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var x: i32 = 0;
   {

executable_semantics/testdata/break1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var x: i32 = 2;
   while (true) {

executable_semantics/testdata/choice1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 choice Ints {
   None,
   One(i32),

executable_semantics/testdata/class1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class_field_access_mismatch.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class_field_access_mismatch.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/class_field_access_mismatch.carbon:11: class Point does not have a field named z
+COMPILATION ERROR: executable_semantics/testdata/class_field_access_mismatch.carbon:13: class Point does not have a field named z
 EXIT CODE: 255

executable_semantics/testdata/class_field_mismatch.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class_field_mismatch.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/class_field_mismatch.carbon:11: type error in call
+COMPILATION ERROR: executable_semantics/testdata/class_field_mismatch.carbon:13: type error in call
 expected: (x = i32, y = i32)
 actual: (x = i32, z = i32)
 EXIT CODE: 255

executable_semantics/testdata/class_field_missing.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 class Point {
   var x: i32;
   var y: i32;

executable_semantics/testdata/class_field_missing.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/class_field_missing.carbon:11: type error in call
+COMPILATION ERROR: executable_semantics/testdata/class_field_missing.carbon:13: type error in call
 expected: (x = i32, y = i32)
 actual: (x = i32)
 EXIT CODE: 255

executable_semantics/testdata/continue1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var x: auto = 2;
   while (not (x == 0)) {

executable_semantics/testdata/experimental_continuation1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that creating a continuation doesn't do anything.
 
 fn main() -> i32 {

executable_semantics/testdata/experimental_continuation2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test creating and running a continuation.
 
 fn main() -> i32 {

executable_semantics/testdata/experimental_continuation3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test pausing a continuation with `__await` and restarting it with
 // `__run`.
 

executable_semantics/testdata/experimental_continuation4.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Assignment for continuations is shallow, so `k2` refers to the same
 // continuation as `k1`.
 

executable_semantics/testdata/experimental_continuation5.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test access to block-scoped variables upon resuming a continuation.
 
 fn main() -> i32 {

executable_semantics/testdata/experimental_continuation6.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test recursive functions inside continuations.
 
 var current: i32 = 0;

executable_semantics/testdata/experimental_continuation7.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test the way in which copying of continuations interacts with data
 // on the stack such as the variable `x`. In this example the copy
 // happens after the variable `x` is created.

executable_semantics/testdata/experimental_continuation8.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test the way in which copying of continuations interacts with data
 // on the stack such as the variable `x`. In this example the copy
 // happens before the variable `x` is created, so each continuation

executable_semantics/testdata/experimental_continuation9.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that the read from x triggers an error because x is dead.
 // This test also demonstrates how by-reference free-variable capture
 // is dangerous and can happen inside continuations.

executable_semantics/testdata/experimental_continuation9.golden

@@ -1,2 +1,2 @@
-RUNTIME ERROR: executable_semantics/testdata/experimental_continuation9.carbon:12: undefined behavior: access to dead value 1
+RUNTIME ERROR: executable_semantics/testdata/experimental_continuation9.carbon:14: undefined behavior: access to dead value 1
 EXIT CODE: 255

executable_semantics/testdata/fun1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn f(x: i32) -> i32 {
   return x - 1;
 }

executable_semantics/testdata/fun2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // This tests the call-by-value aspect of parameter passing.
 // This makes sure that when the value in `x` dies,
 // it does not cause the value in `a` to also die.

executable_semantics/testdata/fun3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test multiple arguments
 fn f(x: i32, y: i32) -> i32 {
   return x + y;

executable_semantics/testdata/fun4.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test empty parameters and return type
 fn f() { }
 

executable_semantics/testdata/fun5.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn add(x: i32, y: i32) => x + y;
 
 fn main() -> i32 {

executable_semantics/testdata/fun6_fail_type.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn f(x: i32, y: i32) -> i32 { return x + y; }
 
 fn main() -> i32 {

executable_semantics/testdata/fun6_fail_type.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/fun6_fail_type.carbon:10: type error in call
+COMPILATION ERROR: executable_semantics/testdata/fun6_fail_type.carbon:12: type error in call
 expected: (0 = i32, 1 = i32)
 actual: (0 = (0 = i32, 1 = i32))
 EXIT CODE: 255

executable_semantics/testdata/fun_named_params.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn f(x: i32, .d = y: i32) => x + y;
 
 fn main() -> i32 {

executable_semantics/testdata/fun_named_params2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn f(x: i32, .d = y: i32, z: i32, .e = a: i32) => (x + y) - (z + a);
 
 fn main() -> i32 {

executable_semantics/testdata/fun_named_params2.golden

@@ -1,2 +1,2 @@
-PROGRAM ERROR: executable_semantics/testdata/fun_named_params2.carbon:5: positional members must come before named members
+PROGRAM ERROR: executable_semantics/testdata/fun_named_params2.carbon:7: positional members must come before named members
 EXIT CODE: 255

executable_semantics/testdata/fun_recur.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn f(x: i32) -> i32 {
   if (x == 0) {
     return x;

executable_semantics/testdata/funptr1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn add1(x: i32) -> i32 {
   return x + 1;
 }

executable_semantics/testdata/generic_function1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn id[T:! Type](x: T) -> T {
   return x;
 }

executable_semantics/testdata/generic_function2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn fst[T:! Type](x: T, y: T) -> T {
   return x;
 }

executable_semantics/testdata/generic_function3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn snd[T:! Type](x: i32, y: T) -> T {
   return y;
 }

executable_semantics/testdata/generic_function_apply.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn apply[T:! Type, U:! Type](f: fnty (T) -> U, x: T) -> U {
   return f(x);
 }

executable_semantics/testdata/generic_function_fail1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn fst[T:! Type](x: T, y: T) -> T {
   return x;
 }

executable_semantics/testdata/generic_function_fail1.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/generic_function_fail1.carbon:10: type error in argument deduction
+COMPILATION ERROR: executable_semantics/testdata/generic_function_fail1.carbon:12: type error in argument deduction
 expected: i32
 actual: Bool
 EXIT CODE: 255

executable_semantics/testdata/generic_function_fail2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn id[T:! Type](x: i32) -> i32 {
   return x;
 }

executable_semantics/testdata/generic_function_fail2.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/generic_function_fail2.carbon:10: could not deduce type argument for type parameter T
+COMPILATION ERROR: executable_semantics/testdata/generic_function_fail2.carbon:12: could not deduce type argument for type parameter T
 EXIT CODE: 255

executable_semantics/testdata/generic_function_fail3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn id[T:! Type](x: T) -> T {
   return x + 0;
 }

executable_semantics/testdata/generic_function_fail3.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/generic_function_fail3.carbon:6: type error in addition(1)
+COMPILATION ERROR: executable_semantics/testdata/generic_function_fail3.carbon:8: type error in addition(1)
 expected: i32
 actual: T
 EXIT CODE: 255

executable_semantics/testdata/generic_function_swap.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn swap[T:! Type, U:! Type](tuple: (T, U)) -> (U, T) {
   return (tuple[1], tuple[0]);
 }

executable_semantics/testdata/generic_function_tuple_map.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn map[T:! Type](f: fnty (T) -> T, tuple: (T, T)) -> (T, T) {
   return (f(tuple[0]), f(tuple[1]));
 }

executable_semantics/testdata/global_variable1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test global variable initialization and read.
 
 var zero: i32 = 0;

executable_semantics/testdata/global_variable2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that mutations to a global variable in one function is visible
 // in another function.
 

executable_semantics/testdata/global_variable3.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test type checking of global variable. Error expected.
 
 var flag: i32 = true;

executable_semantics/testdata/global_variable3.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/global_variable3.carbon:7: type error in initializer of variable
+COMPILATION ERROR: executable_semantics/testdata/global_variable3.carbon:9: type error in initializer of variable
 expected: i32
 actual: Bool
 EXIT CODE: 255

executable_semantics/testdata/global_variable4.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test mutation of a global variable.
 
 var zero: i32 = 1;

executable_semantics/testdata/global_variable5.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test overshadowing of global variable.
 
 var x: i32 = 1;

executable_semantics/testdata/global_variable5.golden

@@ -1,4 +1,4 @@
-COMPILATION ERROR: executable_semantics/testdata/global_variable5.carbon:10: type error in return
+COMPILATION ERROR: executable_semantics/testdata/global_variable5.carbon:12: type error in return
 expected: ()
 actual: i32
 EXIT CODE: 255

executable_semantics/testdata/global_variable6.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test a global variable depending on another global.
 
 var x: i32 = 0;

executable_semantics/testdata/global_variable7.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test a global variable depending on a function.
 
 fn f() -> i32 {

executable_semantics/testdata/global_variable8.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 // Test that a global variable may not depend on a later global.
 // Error expected.
 

executable_semantics/testdata/global_variable8.golden

@@ -1,2 +1,2 @@
-RUNTIME ERROR: executable_semantics/testdata/global_variable8.carbon:8: could not find `y`
+RUNTIME ERROR: executable_semantics/testdata/global_variable8.carbon:10: could not find `y`
 EXIT CODE: 255

executable_semantics/testdata/if_else.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (0 == 1) {
     return 1;

executable_semantics/testdata/if_else_if.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (0 == 1) {
     return 1;

executable_semantics/testdata/if_else_if_else.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (0 == 1) {
     return 1;

executable_semantics/testdata/if_false.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (0 == 1) {
     return 1;

executable_semantics/testdata/if_nesting.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (0 == 0) {
     if (0 == 1) {

executable_semantics/testdata/if_true.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   if (1 == 1) {
     return 0;

executable_semantics/testdata/ignored_parameter.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn ReturnSecond(_: i32, x: i32) -> i32 {
   return x;
 }

executable_semantics/testdata/import_late.carbon

@@ -0,0 +1,11 @@
+// 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
+
+package ExecutableSemanticsTest api;
+
+fn main() -> i32 {
+  return 0;
+}
+
+import ExecutableSemanticsTest library "Nonexistent";

executable_semantics/testdata/import_late.golden

@@ -0,0 +1,2 @@
+COMPILATION ERROR: executable_semantics/testdata/import_late.carbon:11: syntax error, unexpected IMPORT, expecting END_OF_FILE
+EXIT CODE: 255

executable_semantics/testdata/import_nonexistent_library.carbon

@@ -0,0 +1,11 @@
+// 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
+
+package ExecutableSemanticsTest api;
+
+import Nonexistent;
+
+fn main() -> i32 {
+  return 0;
+}

executable_semantics/testdata/import_nonexistent_library.golden

@@ -0,0 +1 @@
+result: 0

executable_semantics/testdata/import_nonexistent_package.carbon

@@ -0,0 +1,11 @@
+// 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
+
+package ExecutableSemanticsTest api;
+
+import ExecutableSemanticsTest library "Nonexistent";
+
+fn main() -> i32 {
+  return 0;
+}

executable_semantics/testdata/import_nonexistent_package.golden

@@ -0,0 +1 @@
+result: 0

executable_semantics/testdata/match_any_int.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var t: auto = 5;
   match (t) {

executable_semantics/testdata/match_int.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var t: auto = 5;
   match (t) {

executable_semantics/testdata/match_int_default.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var t: auto = 5;
   match (t) {

executable_semantics/testdata/match_placeholder.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var t: auto = (1, 2, 3, 4);
   match (t) {

executable_semantics/testdata/next.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main () -> i32
 {
   var x: i32 = 0;

executable_semantics/testdata/no_match.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var x: i32 = 0;
   match (x) {

executable_semantics/testdata/package_library.carbon

@@ -0,0 +1,9 @@
+// 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
+
+package ExecutableSemanticsTest library "Foo" api;
+
+fn main() -> i32 {
+  return 0;
+}

executable_semantics/testdata/package_library.golden

@@ -0,0 +1 @@
+result: 0

executable_semantics/testdata/package_missing.carbon

@@ -0,0 +1,7 @@
+// 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
+
+fn main() -> i32 {
+  return 0;
+}

executable_semantics/testdata/package_missing.golden

@@ -0,0 +1,2 @@
+COMPILATION ERROR: executable_semantics/testdata/package_missing.carbon:5: syntax error, unexpected FN, expecting PACKAGE
+EXIT CODE: 255

executable_semantics/testdata/pattern_init.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var (x: auto, y: auto) = (2, 3);
   return y - x - 1;

executable_semantics/testdata/pattern_variable_fail.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   // error
   x : i32;

executable_semantics/testdata/pattern_variable_fail.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/pattern_variable_fail.carbon:7: syntax error, unexpected COLON
+COMPILATION ERROR: executable_semantics/testdata/pattern_variable_fail.carbon:9: syntax error, unexpected COLON
 EXIT CODE: 255

executable_semantics/testdata/placeholder_variable.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var _: auto = 1;
   return 0;

executable_semantics/testdata/print1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var s: auto = "Hello world!\n";
   Print(s);

executable_semantics/testdata/record1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn main() -> i32 {
   var t2: (.x = i32, .y = i32) = (.x = 2, .y = 5);
   t2.y = 3;

executable_semantics/testdata/return_auto.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() -> auto {
   return 0;
 }

executable_semantics/testdata/return_auto.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/return_auto.carbon:5: syntax error, unexpected AUTO
+COMPILATION ERROR: executable_semantics/testdata/return_auto.carbon:7: syntax error, unexpected AUTO
 EXIT CODE: 255

executable_semantics/testdata/return_empty_explicit.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() -> () {
   return ();
 }

executable_semantics/testdata/return_empty_explicit_fail.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() {
   return ();
 }

executable_semantics/testdata/return_empty_explicit_fail.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/return_empty_explicit_fail.carbon:6: return (); should not provide a return value, to match the function's signature.
+COMPILATION ERROR: executable_semantics/testdata/return_empty_explicit_fail.carbon:8: return (); should not provide a return value, to match the function's signature.
 EXIT CODE: 255

executable_semantics/testdata/return_empty_implicit1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() {
 }
 

executable_semantics/testdata/return_empty_implicit2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() {
   return;
 }

executable_semantics/testdata/return_empty_implicit_fail1.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() -> () {
 }
 

executable_semantics/testdata/return_empty_implicit_fail1.golden

@@ -1,2 +1,2 @@
-COMPILATION ERROR: executable_semantics/testdata/return_empty_implicit_fail1.carbon:6: control-flow reaches end of function that provides a `->` return type without reaching a return statement
+COMPILATION ERROR: executable_semantics/testdata/return_empty_implicit_fail1.carbon:8: control-flow reaches end of function that provides a `->` return type without reaching a return statement
 EXIT CODE: 255

executable_semantics/testdata/return_empty_implicit_fail2.carbon

@@ -2,6 +2,8 @@
 // Exceptions. See /LICENSE for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
+package ExecutableSemanticsTest api;
+
 fn F() -> () {
   return;
 }