cmd/compile: conversion from int/float typed constant to complex variable changed in 1.14 [1.14 backport]

[gopherbot]

@ianlancetaylor requested issue #38117 to be considered for backport to the next 1.14 minor release.

Looks like we're going back to the 1.13 behavior. I'll let @griesemer review the CL, but:

@gopherbot Please open a backport to 1.14.

The compiler behavior changed the way it handles constant conversions. This can break existing programs with no workaround other than rewriting the program, which should not be needed.

[andybons]

Approved as this is a regression with no workaround.

[gopherbot]

Change https://golang.org/cl/232719 mentions this issue: [release-branch.go1.14] cmd/compile: fix constant conversion involving complex types

[gopherbot]

Closed by merging f4274e6 to release-branch.go1.14.