tests: Add testcases for yield from.

tests/basics/gen-yield-from-close.py

@@ -0,0 +1,87 @@
+def gen():
+    yield 1
+    yield 2
+    yield 3
+    yield 4
+
+def gen2():
+    yield -1
+    print((yield from gen()))
+    yield 10
+    yield 11
+
+g = gen2()
+print(next(g))
+print(next(g))
+g.close()
+try:
+    print(next(g))
+except StopIteration:
+    print("StopIteration")
+
+
+# Now variation of same test, but with leaf generator
+# swallowing GeneratorExit exception - its upstream gen
+# generator should still receive one.
+def gen3():
+    yield 1
+    try:
+        yield 2
+    except GeneratorExit:
+        print("leaf caught GeneratorExit and swallowed it")
+        return
+    yield 3
+    yield 4
+
+def gen4():
+    yield -1
+    try:
+        print((yield from gen3()))
+    except GeneratorExit:
+        print("delegating caught GeneratorExit")
+        raise
+    yield 10
+    yield 11
+
+g = gen4()
+print(next(g))
+print(next(g))
+print(next(g))
+g.close()
+try:
+    print(next(g))
+except StopIteration:
+    print("StopIteration")
+
+
+# Yet another variation - leaf generator gets GeneratorExit,
+# but raises StopIteration instead. This still should close chain properly.
+def gen5():
+    yield 1
+    try:
+        yield 2
+    except GeneratorExit:
+        print("leaf caught GeneratorExit and raised StopIteration instead")
+        raise StopIteration(123)
+    yield 3
+    yield 4
+
+def gen6():
+    yield -1
+    try:
+        print((yield from gen5()))
+    except GeneratorExit:
+        print("delegating caught GeneratorExit")
+        raise
+    yield 10
+    yield 11
+
+g = gen6()
+print(next(g))
+print(next(g))
+print(next(g))
+g.close()
+try:
+    print(next(g))
+except StopIteration:
+    print("StopIteration")

tests/basics/gen-yield-from-exc.py

@@ -0,0 +1,13 @@
+def gen():
+    yield 1
+    yield 2
+    raise ValueError
+
+def gen2():
+    try:
+        print((yield from gen()))
+    except ValueError:
+        print("caught ValueError from downstream")
+
+g = gen2()
+print(list(g))

tests/basics/gen-yield-from-send.py

@@ -0,0 +1,14 @@
+def gen():
+    print("sent:", (yield 1))
+    yield 2
+
+def gen2():
+    print((yield from gen()))
+
+g = gen2()
+next(g)
+print("yielded:", g.send("val"))
+try:
+    next(g)
+except StopIteration:
+    print("StopIteration")

tests/basics/gen-yield-from-throw.py

@@ -0,0 +1,19 @@
+def gen():
+    try:
+        yield 1
+    except ValueError:
+        print("got ValueError from upstream!")
+    yield "str1"
+    raise TypeError
+
+def gen2():
+    print((yield from gen()))
+
+g = gen2()
+print(next(g))
+print(g.throw(ValueError))
+try:
+    print(next(g))
+except TypeError:
+    print("got TypeError from downstream!")
+

tests/basics/gen-yield-from.py

@@ -0,0 +1,42 @@
+# Case of terminating subgen using return with value
+def gen():
+    yield 1
+    yield 2
+    return 3
+
+def gen2():
+    print("here1")
+    print((yield from gen()))
+    print("here2")
+
+g = gen2()
+print(list(g))
+
+
+# Like above, but terminate subgen using StopIteration
+def gen3():
+    yield 1
+    yield 2
+    raise StopIteration
+
+def gen4():
+    print("here1")
+    print((yield from gen3()))
+    print("here2")
+
+g = gen4()
+print(list(g))
+
+# Like above, but terminate subgen using StopIteration with value
+def gen5():
+    yield 1
+    yield 2
+    raise StopIteration(123)
+
+def gen6():
+    print("here1")
+    print((yield from gen5()))
+    print("here2")
+
+g = gen6()
+print(list(g))