SILOptimizer: Re-implement escaping capture diagnostics

The new pass is based on existing asserts in DiagnoseStaticExclusivity.
They were compiled out in release builds and only checked for captures of
inout parameters. This patch converts the assertions into diagnostics and
adds checks for captures of non-escaping function values.

Unlike the Sema-based checks that this replaces, the new code handles
transitive captures from recursive local functions, which means certain
invalid code that used to compile will now be rejected with an error.

The new analysis also looks at the ultimate usages of a local function
instead of just assuming all local functions are escaping, which fixes
issues where the compiler would reject valid code.

Fixes a bunch of related issues, including:

- <rdar://problem/29403178>
- <https://bugs.swift.org/browse/SR-8546> / <rdar://problem/43355341>
- <https://bugs.swift.org/browse/SR-9043> / <rdar://problem/45511834>

Author: slavapestov

include/swift/AST/DiagnosticsSIL.def

@@ -116,6 +116,27 @@ ERROR(unsupported_c_function_pointer_conversion,none,
 ERROR(objc_selector_malformed,none,"the type ObjectiveC.Selector is malformed",
       ())
 
+// Invalid escaping capture diagnostics.
+ERROR(escaping_inout_capture,none,
+      "escaping closure captures 'inout' parameter %0", (Identifier))
+NOTE(inout_param_defined_here,none,
+     "parameter %0 is declared 'inout'", (Identifier))
+ERROR(escaping_mutable_self_capture,none,
+      "escaping closure captures mutating 'self' parameter", ())
+
+ERROR(escaping_noescape_param_capture,none,
+      "escaping closure captures non-escaping parameter %0", (Identifier))
+NOTE(noescape_param_defined_here,none,
+     "parameter %0 is implicitly non-escaping", (Identifier))
+
+ERROR(escaping_noescape_var_capture,none,
+      "escaping closure captures non-escaping value", ())
+
+NOTE(value_captured_here,none,"captured here", ())
+
+NOTE(value_captured_transitively,none,
+     "captured indirectly by this call", ())
+
 // Definite initialization diagnostics.
 NOTE(variable_defined_here,none,
      "%select{variable|constant}0 defined here", (bool))

include/swift/SILOptimizer/PassManager/Passes.def

@@ -134,6 +134,8 @@ PASS(Devirtualizer, "devirtualizer",
      "Indirect Call Devirtualization")
 PASS(DiagnoseInfiniteRecursion, "diagnose-infinite-recursion",
      "Diagnose Infinitely-Recursive Code")
+PASS(DiagnoseInvalidEscapingCaptures, "diagnose-invalid-escaping-captures",
+     "Diagnose Invalid Escaping Captures")
 PASS(DiagnoseStaticExclusivity, "diagnose-static-exclusivity",
      "Static Enforcement of Law of Exclusivity")
 PASS(DiagnoseUnreachable, "diagnose-unreachable",

lib/SILOptimizer/Mandatory/CMakeLists.txt

@@ -7,6 +7,7 @@ silopt_register_sources(
   DIMemoryUseCollector.cpp
   DataflowDiagnostics.cpp
   DiagnoseInfiniteRecursion.cpp
+  DiagnoseInvalidEscapingCaptures.cpp
   DiagnoseStaticExclusivity.cpp
   DiagnoseUnreachable.cpp
   GuaranteedARCOpts.cpp