Go patch committed: Fix double evaluation when using interface field expression

[Ian Lance Taylor <iant at golang dot org>]

This patch to the Go frontend by Cherry Zhang fixes the compiler to
avoid a double evaluation of an interface field expression.  In
Interface_field_reference_expression, the interface expression is used
in two places, so a temporary variable is used.  Previously, we used a
Set_and_use_temporary_expression, which, when evaluated twice, causes
double evaluation of the underlying expression.  Fix by setting the
temporary once and use Temporary_reference_expression instead.

This fixes https://golang.org/issue/26248.  The test case for this is
in https://golang.org/cl/122757.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Attachment: patch.txt
Description: Text document