Vedant Kumar 60ec3f1b90 Fix debug description for cases with multiple items (#32282) ...

* [SILGenFunction] Don't create redundant nested debug scopes

Instead of emitting:

```
sil_scope 4 { loc "main.swift":6:19 parent 3 }
sil_scope 5 { loc "main.swift":7:3 parent 4 }
sil_scope 6 { loc "main.swift":7:3 parent 5 }
sil_scope 7 { loc "main.swift":7:3 parent 5 }
sil_scope 8 { loc "main.swift":9:5 parent 4 }
```

Emit:

```
sil_scope 4 { loc "main.swift":6:19 parent 3 }
sil_scope 5 { loc "main.swift":7:3 parent 4 }
sil_scope 6 { loc "main.swift":9:5 parent 5 }
```

* [IRGenSIL] Diagnose conflicting shadow copies

If we attempt to store a value with the wrong type into a slot reserved
for a shadow copy, diagnose what went wrong.

* [SILGenPattern] Defer debug description of case variables

Create unique nested debug scopes for a switch, each of its case labels,
and each of its case bodies. This looks like:

```
  switch ... { // Enter scope 1.
    case ... : // Enter scope 2, nested within scope 1.
      <body-1> // Enter scope 3, nested within scope 2.

    case ... : // Enter scope 4, nested within scope 1.
      <body-2> // Enter scope 5, nested within scope 4.
  }
```

Use the new scope structure to defer emitting debug descriptions of case
bindings. Specifically, defer the work until we can nest the scope for a
case body under the scope for a pattern match.

This fixes SR-7973, a problem where it was impossible to inspect a case
binding in lldb when stopped at a case with multiple items.

Previously, we would emit the debug descriptions too early (in the
pattern match), leading to duplicate/conflicting descriptions. The only
reason that the ambiguous description was allowed to compile was because
the debug scopes were nested incorrectly.

rdar://41048339

* Update tests

2020-06-10 13:31:10 -07:00

4.0 KiB

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