design/32437-try-builtin.md: clarify prose per suggestion from Yves Junqueira
See https://golang.org/issues/32437#issuecomment-498892164 for
details.
Change-Id: I223749527b9649586d39aeb38da592f35fcc7e6f
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/180637
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/design/32437-try-builtin.md b/design/32437-try-builtin.md
index 397d722..15fba6c 100644
--- a/design/32437-try-builtin.md
+++ b/design/32437-try-builtin.md
@@ -62,7 +62,7 @@
x1, … xn = t1, … tn // assignment only if there was no error
```
-In other words, if the last argument supplied to `try`, of type `error`, is not nil, the enclosing function’s error result variable (called `err` in the pseudo-code above, but it may have any other name or be unnamed) is set to that non-nil error value before the enclosing function returns. If the enclosing function declares other named result parameters, those result parameters keep whatever value they have. If the function declares other unnamed result parameters, they assume their corresponding zero values (which is the same as keeping the value they already have).
+In other words, if the last argument supplied to `try`, of type `error`, is not nil, the enclosing function’s error result variable (called `err` in the pseudo-code above, but it may have any other name or be unnamed) is set to that non-nil error value and the enclosing function returns. If the enclosing function declares other named result parameters, those result parameters keep whatever value they have. If the function declares other unnamed result parameters, they assume their corresponding zero values (which is the same as keeping the value they already have).
If `try` happens to be used in a multiple assignment as in this illustration, and a non-nil error is detected, the assignment (to the user-defined variables) is _not_ executed and none of the variables on the left-hand side of the assignment are changed. That is, `try` behaves like a function call: its results are only available if `try` returns to the actual call site (as opposed to returning from the enclosing function). As a consequence, if the variables on the left-hand side are named result parameters, using `try` will lead to a different result than typical code found today. For instance, if `a`, `b`, and `err` are all named result parameters of the enclosing function, this code
