Add more context to dyn-compatibility diagnostic for receiver-less associated functions

[xyz-harshal]

Fixes #159492

Expands the two suggestion messages for the "no self parameter"
dyn-compatibility violation to explain why each fix works, per the issue.

Before:
help: consider turning create into a method by giving it a &self argument
help: alternatively, consider constraining create so it does not apply to trait objects

After:
help: consider turning create into a method by giving it a &self argument, so that it is accessible through the trait object's vtable
help: alternatively, consider constraining create so it is explicitly marked as not applying to trait objects

Only the two strings in DynCompatibilityViolationSolution::add_to
(rustc_middle/src/traits/mod.rs) changed — no logic, applicability, or span changes.

Added a regression test using the issue's exact example
(tests/ui/dyn-compatibility/static-constructor-prevents-dyn-no-api-guidance.rs).

Verified against a locally-built rustc; full tests/ui suite passes
(21643 passed, 0 failed). Note: next-solver compare-mode has pre-existing,
unrelated failures on 3 tests in this directory, confirmed present on main
without this diff.

[rustbot]

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[rustbot]

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  • 38e36f6

[Copilot]

Pull request overview

This PR improves the dyn-compatibility diagnostic guidance for receiver-less associated functions by expanding the two existing “no self parameter” help suggestions to explain why each suggested fix works, and adds a regression test based on the reported issue example.

Changes:

• Expand the “add &self” suggestion to explain vtable accessibility for trait objects.
• Expand the “add where Self: Sized” suggestion to clarify it explicitly excludes the item from applying to trait objects.
• Update UI stderr expectations across affected tests and add a dedicated regression test case.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
compiler/rustc_middle/src/traits/mod.rs	Updates the two help suggestion strings emitted for the “no self parameter” dyn-compatibility violation.
tests/ui/dyn-compatibility/static-constructor-prevents-dyn-no-api-guidance.rs	Adds a regression test reproducing the issue’s minimal example.
tests/ui/dyn-compatibility/static-constructor-prevents-dyn-no-api-guidance.stderr	New expected output validating the expanded help messages in a real-world scenario.
tests/ui/traits/object/safety.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/traits/object/canonicalize-fresh-infer-vars-issue-103626.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/traits/missing-for-type-in-impl.e2015.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/traits/issue-72410.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/suggestions/dyn-incompatible-trait-should-use-where-sized.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/suggestions/dyn-incompatible-trait-should-use-self.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/suggestions/dyn-incompatible-trait-should-use-self-2021.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/statics/unsizing-wfcheck-issue-127299.stderr	Updates expected help text to match the expanded diagnostic strings (both occurrences).
tests/ui/parallel-rustc/recursive-trait-fn-sig-issue-142064.stderr	Updates expected help text to match the expanded diagnostic strings (both occurrences).
tests/ui/impl-trait/dyn-incompatible-trait-in-return-position-dyn-trait.stderr	Updates expected help text to match the expanded diagnostic strings (all occurrences).
tests/ui/dyn-compatibility/taint-const-eval.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/dyn-compatibility/spurious-dyn-compat-errors-58734.stderr	Updates expected help text to match the expanded diagnostic strings.
tests/ui/dyn-compatibility/no-static.stderr	Updates expected help text to match the expanded diagnostic strings (both occurrences).
tests/ui/dyn-compatibility/dyn-incompat-const-slice.stderr	Updates expected help text to match the expanded diagnostic strings (both occurrences).
tests/ui/dyn-compatibility/avoid-ice-on-warning-3.old.stderr	Updates expected help text to match the expanded diagnostic strings.

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