Restrict shape expression to terms and patterns

[liufengyun]

Restrict shape expression to terms and patterns

Rationale

Shape expression for types are not readable and they are not supported in any other languages. Therefore, it is better to remove the support.

Checklist

• Added / updated tests under tests/pos/ or tests/warn/
• Docs updated if the change affects user-visible behavior
• All commits are signed off (why?)

How to sign off commits

Use git commit -s to add the Signed-off-by line automatically:

To add a sign-off to the last commit retroactively:

git commit --amend -s --no-edit

To add sign-off to the last 3 commits:

git rebase --signoff HEAD~3

Security impact

No