compiletest: Make diagnostic kind mandatory on line annotations

[petrochenkov]

Proposal

This is an MCP for PR rust-lang/rust#139720.

Compiletest currently accepts line annotations without kind in UI tests.

    let a = b + c; //~ my message

Such annotations have two effects.

• First, they match any compiler-produced diagnostic kind. This functionality is never used in practice, there are no target-dependent diagnostic kinds of something like that.
• Second, they are not "viral". For example, any explicit //~ NOTE my msg in a test requires all other NOTE diagnostics in the same test to be annotated. Implicit //~ my msg will just match the note and won't require other annotations.

The second functionality has a replacement since recently - directive //@ dont-require-annotations: NOTE.

The proposal is to remove support for //~ my message annotations and always require specifying the kind.
Unwanted additional annotations can be suppressed using the dont-require-annotations directive if necessary.

Mentors or Reviewers

@jieyouxu

Process

The main points of the Major Change Process are as follows:

• File an issue describing the proposal.
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• Once an MCP is seconded, the Final Comment Period begins. If no objections are raised after 10 days, the MCP is considered approved.

You can read more about Major Change Proposals on forge.

[rustbot]

Important

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cc @rust-lang/compiler

[oli-obk]

@rustbot second