v2.1.3: Code quality, documentation, and test improvements

[mkenney]

Added

• Doc comments added to previously undocumented exported and internal symbols:
  • Tmap type
  • ErrorSignedToUnsigned, ErrorInvalidOption, ErrorStrErrorCastingFunc, ErrorStrUnableToCast (clarifying the string vars are format strings, not error values)
  • castToType — all 8 dispatch cases documented
• New godoc examples: ExampleTo_map, ExampleTo_struct, ExampleToE_mapDuplicateKeyError, ExampleToE_structNested, ExampleToE_structStrict, ExampleToE_mapToPrivateStruct.

Changed

• Renamed the sentinel error variable Error to ErrorUnableToCast. Error is retained as a deprecated alias with a // Deprecated: godoc annotation for backward compatibility.
• Example function suffixes converted from snake_case to camelCase (e.g. ExampleToE_mapFromMap) so all examples appear in godoc. Suffixes containing underscores are silently dropped by godoc.

Fixed

• ToE doc referenced non-existent type Ops (correct type is Op) and contained double word "the the" — corrected.
• ToStructE doc omitted *struct as a valid source type — corrected.
• toSlice doc was circular and meaningless — rewritten.
• ops.Global doc omitted FORMAT from the global flag list and DECODE from the local flag list — corrected.
• parseOps doc omitted FORMAT and DECODE from its description of preserved values — corrected.
• ops struct doc incorrectly stated all non-default flags are pre-parsed to bool; FORMAT and DECODE are stored as strings — corrected.
• TestPointerDerefLoop "pointer-to-interface" sub-test used errors.New whose concrete pointer type is opaque; replaced with a local ptrReceiverError type that has Error() on *T only, making the pointer-receiver guard explicit and self-documenting.

[Copilot]

Pull request overview

This PR is a v2.1.3 maintenance release focused on documentation, test clarity, and a backwards-compatible rename of the sentinel error variable. It renames Error to ErrorUnableToCast (keeping Error as a deprecated alias), adds doc comments to previously undocumented symbols, fixes several doc inaccuracies, renames example functions from snake_case suffixes to camelCase so godoc surfaces them, and adds new godoc examples.

Changes:

• Rename sentinel error Error → ErrorUnableToCast (with deprecated alias) and update all test assertions.
• Documentation fixes/additions across to.go, to.type.go, to.struct.go, to.slice.go, util.reflect.go, including correcting the global/local flag lists (FORMAT/DECODE).
• Rename example functions and add new godoc examples (map/struct conversions, duplicate-key, strict mode, private fields).

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
to.type.go	Adds ErrorUnableToCast, deprecated Error alias, doc comments for sentinel/format strings, ops/Tmap/parseOps doc fixes.
to.go	Doc grammar fixes for To/ToE.
to.struct.go	Doc clarifies *struct source; switches to ErrorUnableToCast.
to.slice.go	Rewritten toSlice doc comment.
util.reflect.go	Adds dispatch order doc to castToType.
test.examples_test.go	Renames examples to camelCase, adds new examples, removes commented-out block.
CHANGELOG.md	Adds v2.1.3 entry.
to.*_test.go (many)	Mechanical rename of cast.Error → cast.ErrorUnableToCast in assertions and messages, minor gofmt alignment.
test.panic_test.go, test.options_test.go	Same rename in tests.

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[Copilot]

Pull request overview

Copilot reviewed 26 out of 26 changed files in this pull request and generated 1 comment.