Fix [mutating] generic methods (#1618)

Slang generates code that turns the implicit `this` parameter of a method into an explicit parameter. The logic that decides whether that parameter should be `inout` is a bit involved, and there was a bug where a generic method would lead to the use of an `in` modifier (the default) and override the `inout` modifier that was requested by the method itself.

This change fixes the logic to treat generic declarations in the parent chain of a leaf method as having no bearing on whether an implicit `this` parameter should be `inout` or not.

A test case is included that breaks with the old behavior, and demonstrates that a generic `[mutating]` method can now work correctly.

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/bugs/mutating/mutating-generic-method.slang.expected.txt b/tests/bugs/mutating/mutating-generic-method.slang.expected.txt
new file mode 100644
index 000000000..5ac358274
--- /dev/null
+++ b/tests/bugs/mutating/mutating-generic-method.slang.expected.txt
@@ -0,0 +1,4 @@
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