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/generic_function/apply.carbon

@@ -0,0 +1,28 @@
+// 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: -2
+
+package ExecutableSemanticsTest api;
+
+fn apply[T:! Type, U:! Type](f: fnty (T) -> U, x: T) -> U {
+  return f(x);
+}
+
+fn positive(x: Bool) -> i32 {
+  if (x) {
+    return 2;
+  } else {
+    return -2;
+  }
+}
+
+fn main() -> i32 {
+  return apply(positive, false);
+}

executable_semantics/testdata/generic_function/fail_not_addable.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/generic_function/fail_not_addable.carbon:17: type error in addition(1)
+// CHECK: expected: i32
+// CHECK: actual: T
+
+package ExecutableSemanticsTest api;
+
+fn id[T:! Type](x: T) -> T {
+  return x + 0;
+}
+
+fn main() -> i32 {
+  return id(0);
+}

executable_semantics/testdata/generic_function/fail_type_deduction_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/generic_function/fail_type_deduction_mismatch.carbon:21: type error in argument deduction
+// CHECK: expected: i32
+// CHECK: actual: Bool
+
+package ExecutableSemanticsTest api;
+
+fn fst[T:! Type](x: T, y: T) -> T {
+  return x;
+}
+
+fn main() -> i32 {
+  return fst(0, true);
+}

executable_semantics/testdata/generic_function/fail_type_deduction_unused.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: 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/generic_function/fail_type_deduction_unused.carbon:19: could not deduce type argument for type parameter T
+
+package ExecutableSemanticsTest api;
+
+fn id[T:! Type](x: i32) -> i32 {
+  return x;
+}
+
+fn main() -> i32 {
+  return id(0);
+}

executable_semantics/testdata/generic_function/non_generic_param.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: 1
+
+package ExecutableSemanticsTest api;
+
+fn snd[T:! Type](x: i32, y: T) -> T {
+  return y;
+}
+
+fn main() -> i32 {
+  return snd(0, 1);
+}

executable_semantics/testdata/generic_function/return_val.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;
+
+fn id[T:! Type](x: T) -> T {
+  return x;
+}
+
+fn main() -> i32 {
+  return id(0);
+}

executable_semantics/testdata/generic_function/swap.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;
+
+fn swap[T:! Type, U:! Type](tuple: (T, U)) -> (U, T) {
+  return (tuple[1], tuple[0]);
+}
+
+fn main() -> i32 {
+  return swap((0, true))[1];
+}

executable_semantics/testdata/generic_function/tuple_map.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: 1
+
+package ExecutableSemanticsTest api;
+
+fn map[T:! Type](f: fnty (T) -> T, tuple: (T, T)) -> (T, T) {
+  return (f(tuple[0]), f(tuple[1]));
+}
+
+fn inc(x: i32) -> i32 { return x + 1; }
+
+fn main() -> i32 {
+  return map(inc, (0, 2))[0];
+}

executable_semantics/testdata/generic_function/type_matching.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;
+
+fn fst[T:! Type](x: T, y: T) -> T {
+  return x;
+}
+
+fn main() -> i32 {
+  return fst(0, 1);
+}