3a309ba4eb
This PR improves the error message encountered in the case of a type class instance resolution failure, and adds an error explanation that discusses the common new-user case of binary operation overloading and points to the `trace.Meta.synthInstance` option for advanced debugging. ## Example ```lean4 def f (x : String) := x + x ``` Before: ``` failed to synthesize HAdd String String ?m.5 Hint: Additional diagnostic information may be available using the `set_option diagnostics true` command. ``` After: ``` failed to synthesize instance of type class HAdd String String ?m.5 Hint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command. Error code: lean.failedToSynthesizeTypeclassInstance [View explanation](https://lean-lang.org/doc/reference/latest/find/?domain=Manual.errorExplanation&name=lean.failedToSynthesizeTypeclassInstance) ``` The error message is changed in three important ways: * Explains *what* failed to synthesize, using the "type class" terminology that's more likely to be recognized than the "instance" terminology * Points to the `trace.Meta.synthInstance` option which is otherwise nearly undiscoverable but is quite powerful (see also leanprover/reference-manual#663 which is adding commentary on this option) * Gives an error explanation link (which won't actually work until the next release after this is merged) which prioritizes the common-case explanation of using the wrong binary operation
36 lines
1.5 KiB
Text
36 lines
1.5 KiB
Text
{"version": 1,
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"uri": "file:///strInterpSynthError.lean",
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"diagnostics":
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[{"source": "Lean 4",
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"severity": 1,
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"range":
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{"start": {"line": 15, "character": 25},
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"end": {"line": 15, "character": 28}},
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"message":
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"failed to synthesize instance of type class\n ToString Bar\n\nHint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.",
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"fullRange":
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{"start": {"line": 15, "character": 25},
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"end": {"line": 15, "character": 28}},
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"code": "lean.synthInstanceFailed"},
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{"source": "Lean 4",
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"severity": 1,
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"range":
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"end": {"line": 20, "character": 18}},
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"message":
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"failed to synthesize instance of type class\n ToString Bar\n\nHint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.",
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"fullRange":
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{"start": {"line": 20, "character": 15},
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"end": {"line": 20, "character": 18}},
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"code": "lean.synthInstanceFailed"},
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{"source": "Lean 4",
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"severity": 1,
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"range":
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"end": {"line": 26, "character": 20}},
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"message":
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"failed to synthesize instance of type class\n ToString Bar\n\nHint: Type class instance resolution failures can be inspected with the `set_option trace.Meta.synthInstance true` command.",
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"fullRange":
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{"start": {"line": 26, "character": 17},
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"end": {"line": 26, "character": 20}},
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"code": "lean.synthInstanceFailed"}]}
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