Reorganize tests into dirs and rename numbered tests (#825)

There's a small update to update_checks.py to handle the recursive directories. Also, I'm only using one level of nesting in this PR but really no reason we can't do more. I'm just not sure what clustering is best right now.

As a pattern, I'm trying to name all failing tests `fail_*.carbon`.

executable_semantics/testdata/global_variable/fail_init_order.carbon

@@ -0,0 +1,23 @@
+// 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
+//
+// RUN: not executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: not executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: RUNTIME ERROR: {{.*}}/executable_semantics/testdata/global_variable/fail_init_order.carbon:17: could not find `y`
+
+package ExecutableSemanticsTest api;
+
+// Test that a global variable may not depend on a later global.
+// Error expected.
+
+var x: i32 = y;
+
+var y: i32 = 0;
+
+fn main() -> i32 {
+  return x;
+}

executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon

@@ -0,0 +1,22 @@
+// 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
+//
+// RUN: not executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: not executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/global_variable/fail_init_type_mismatch.carbon:18: type error in initializer of variable
+// CHECK: expected: i32
+// CHECK: actual: Bool
+
+package ExecutableSemanticsTest api;
+
+// Test type checking of global variable. Error expected.
+
+var flag: i32 = true;
+
+fn main() -> i32 {
+  return 0;
+}

executable_semantics/testdata/global_variable/init_and_read.carbon

@@ -0,0 +1,20 @@
+// 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
+//
+// RUN: executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: result: 0
+
+package ExecutableSemanticsTest api;
+
+// Test global variable initialization and read.
+
+var zero: i32 = 0;
+
+fn main() -> i32 {
+  return zero;
+}

executable_semantics/testdata/global_variable/init_from_function.carbon

@@ -0,0 +1,24 @@
+// 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
+//
+// RUN: executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: result: 0
+
+package ExecutableSemanticsTest api;
+
+// Test a global variable depending on a function.
+
+fn f() -> i32 {
+  return 0;
+}
+
+var y: i32 = f();
+
+fn main() -> i32 {
+  return y;
+}

executable_semantics/testdata/global_variable/init_order.carbon

@@ -0,0 +1,22 @@
+// 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
+//
+// RUN: executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: result: 0
+
+package ExecutableSemanticsTest api;
+
+// Test a global variable depending on another global.
+
+var x: i32 = 0;
+
+var y: i32 = x;
+
+fn main() -> i32 {
+  return y;
+}

executable_semantics/testdata/global_variable/shadowing.carbon

@@ -0,0 +1,26 @@
+// 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
+//
+// RUN: not executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: not executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: COMPILATION ERROR: {{.*}}/executable_semantics/testdata/global_variable/shadowing.carbon:21: type error in return
+// CHECK: expected: ()
+// CHECK: actual: i32
+
+package ExecutableSemanticsTest api;
+
+// Test overshadowing of global variable.
+
+var x: i32 = 1;
+
+fn identity(x: i32) {
+  return x;
+}
+
+fn main() -> i32 {
+  return identity(0);
+}

executable_semantics/testdata/global_variable/write.carbon

@@ -0,0 +1,21 @@
+// 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
+//
+// RUN: executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: result: 0
+
+package ExecutableSemanticsTest api;
+
+// Test mutation of a global variable.
+
+var zero: i32 = 1;
+
+fn main() -> i32 {
+  zero = 0;
+  return zero;
+}

executable_semantics/testdata/global_variable/write_from_function.carbon

@@ -0,0 +1,26 @@
+// 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
+//
+// RUN: executable_semantics %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes=false %s
+// RUN: executable_semantics --trace %s 2>&1 | \
+// RUN:   FileCheck --match-full-lines --allow-unused-prefixes %s
+// AUTOUPDATE: executable_semantics %s
+// CHECK: result: 0
+
+package ExecutableSemanticsTest api;
+
+// Test that mutations to a global variable in one function is visible
+// in another function.
+
+var flag: i32 = 1;
+
+fn flipFlag() {
+  flag = 0;
+}
+
+fn main() -> i32 {
+  flipFlag();
+  return flag;
+}