Per feedback on #7665, this PR switches the default value
table storage from canonical constant inst_ids to
non-canonical.
Furthermore, this PR simplifies the default value support in
check by requiring that the first owned declaration of a
function completely specify all of its default values.
Updates the diagnostic code and tests to reflect this new
stricter requirement.
Updates the pattern matching code to support unspecified default values.
Adds logic to decl and def merge code to diagnose mismatches in defaults
if specified in both places, or if let entirely unspecified.
Per https://github.com/carbon-language/carbon-lang/pull/7521.
Adds a virtual node to `DefaultValuePattern` to end the
`ExprRegionForPattern` before checking the expression
for the default value.
When checking the default value expression, the context
was still configured to interpret expressions as patterns,
which caused some corruption of state with tuple-pattern
subpatterns.
Corrects an assertion failure I found while working on
feedback from #7665.
Adds check functionality to transform the parse node to SemIR. Only
supported for single declarations of functions, re-declaration and
imports to come in a subsequent PR.
Per #7521.
Lucile Rose Nihlen