[sil] Add the ability to create an ExtendedASTNodeLoc that is only used for diagnostics and not for debugging.

We already have entry points for creating an ExtendedASTNodeLoc with an empty
location for diagnostics and a location for debugging. This does the inverse so
one can emit diagnostics that point at a terminator sourceloc without needing to
add a ReturnInst to the instruction which is illegal and would cause the
SILVerifier to assert.

Author: gottesmm

include/swift/SIL/SILLocation.h

@@ -267,7 +267,6 @@ class SILLocation {
 
   SILLocation(ExtendedASTNodeLoc *ext, LocationKind K)
       : storage(ext), kindAndFlags(K, ExtendedASTNodeKind) {
-    assert(ext && !ext->forDebugging.isNull());
   }
 
   SILLocation(SourceLoc L, LocationKind K)
@@ -470,7 +469,8 @@ class RegularLocation : public SILLocation {
   RegularLocation(Decl *D) : SILLocation(ASTNodeTy(D), RegularKind) {}
   RegularLocation(Pattern *P) : SILLocation(ASTNodeTy(P), RegularKind) {}
   RegularLocation(Stmt *S, Pattern *P, SILModule &Module);
-  RegularLocation(SILLocation ForDebuggingOnly, SILModule &Module);
+  RegularLocation(SILLocation ForDebuggingOrDiagnosticsOnly, SILModule &Module,
+                  bool isForDebugOnly = true);
   RegularLocation(SourceLoc L) : SILLocation(L, RegularKind) {}
   RegularLocation(FilenameAndLocation *filePos)
     : SILLocation(filePos, RegularKind) {}
@@ -510,6 +510,15 @@ class RegularLocation : public SILLocation {
     return getAutoGeneratedLocation(L);
   }
 
+  /// Returns a location that uses L for diagnostics but is otherwise an auto
+  /// generated location.
+  static RegularLocation getDiagnosticsOnlyLocation(SILLocation L,
+                                                    SILModule &M) {
+    if (L.isASTNode())
+      return RegularLocation(L, M, false /*is for debug only*/);
+    return getAutoGeneratedLocation(L);
+  }
+
   static bool isKind(const SILLocation& L) {
     return L.getKind() == RegularKind;
   }
@@ -518,6 +527,8 @@ class RegularLocation : public SILLocation {
   RegularLocation() : SILLocation(RegularKind) {}
   static SILLocation::ExtendedASTNodeLoc *
   getDebugOnlyExtendedASTNodeLoc(SILLocation L, SILModule &Module);
+  static SILLocation::ExtendedASTNodeLoc *
+  getDiagnosticOnlyExtendedASTNodeLoc(SILLocation L, SILModule &Module);
 };
 
 /// Used to represent a return instruction in user code.

lib/SIL/IR/SILLocation.cpp

@@ -235,9 +235,25 @@ RegularLocation::getDebugOnlyExtendedASTNodeLoc(SILLocation L,
   return new (Module) ExtendedASTNodeLoc((Decl *)nullptr, P);
 }
 
-RegularLocation::RegularLocation(SILLocation ForDebuggingOnly,
-                                 SILModule &Module)
-    : SILLocation(getDebugOnlyExtendedASTNodeLoc(ForDebuggingOnly, Module),
+SILLocation::ExtendedASTNodeLoc *
+RegularLocation::getDiagnosticOnlyExtendedASTNodeLoc(SILLocation L,
+                                                     SILModule &Module) {
+  if (auto D = L.getAsASTNode<Decl>())
+    return new (Module) ExtendedASTNodeLoc(D, (Decl *)nullptr);
+  if (auto E = L.getAsASTNode<Expr>())
+    return new (Module) ExtendedASTNodeLoc(E, (Decl *)nullptr);
+  if (auto S = L.getAsASTNode<Stmt>())
+    return new (Module) ExtendedASTNodeLoc(S, (Decl *)nullptr);
+  auto P = L.getAsASTNode<Pattern>();
+  return new (Module) ExtendedASTNodeLoc(P, (Decl *)nullptr);
+}
+
+RegularLocation::RegularLocation(SILLocation ForDebuggingOrDiagnosticsOnly,
+                                 SILModule &Module, bool isForDebugOnly)
+    : SILLocation(isForDebugOnly ? getDebugOnlyExtendedASTNodeLoc(
+                                       ForDebuggingOrDiagnosticsOnly, Module)
+                                 : getDiagnosticOnlyExtendedASTNodeLoc(
+                                       ForDebuggingOrDiagnosticsOnly, Module),
                   RegularKind) {
   markAutoGenerated();
 }