[Scope map/parser/AST] Miscellaneous cleanups to avoid producing invalid source ranges.

The scope map relies fairly deeply on having reasonable source ranges
for AST nodes. Fix the construction and query of source ranges in a
few places throughout the parser and AST to provide stronger
invariants.

Author: DougGregor

lib/AST/ASTScope.cpp

@@ -90,7 +90,7 @@ static bool hasAccessors(AbstractStorageDecl *asd) {
   case AbstractStorageDecl::ComputedWithMutableAddress:
   case AbstractStorageDecl::InheritedWithObservers:
   case AbstractStorageDecl::StoredWithObservers:
-    return true;
+    return asd->getBracesRange().isValid();
 
   case AbstractStorageDecl::Stored:
   case AbstractStorageDecl::StoredWithTrivialAccessors:
@@ -1754,7 +1754,8 @@ SmallVector<ValueDecl *, 4> ASTScope::getLocalBindings() const {
     break;
 
   case ASTScopeKind::LocalDeclaration:
-    result.push_back(cast<ValueDecl>(localDeclaration));
+    if (auto value = dyn_cast<ValueDecl>(localDeclaration))
+      result.push_back(value);
     break;
 
   case ASTScopeKind::ConditionalClause:
@@ -1776,8 +1777,10 @@ SmallVector<ValueDecl *, 4> ASTScope::getLocalBindings() const {
     break;
 
   case ASTScopeKind::ForStmtInitializer:
-    for (auto decl : forStmt->getInitializerVarDecls())
-      result.push_back(cast<ValueDecl>(decl));
+    for (auto decl : forStmt->getInitializerVarDecls()) {
+      if (auto value = dyn_cast<ValueDecl>(decl))
+        result.push_back(value);
+    }
     break;
 
   case ASTScopeKind::PatternInitializer:

lib/AST/Decl.cpp

@@ -3832,38 +3832,41 @@ ParamDecl *ParamDecl::createSelf(SourceLoc loc, DeclContext *DC,
 
 /// Return the full source range of this parameter.
 SourceRange ParamDecl::getSourceRange() const {
-  SourceRange range;
-  
   SourceLoc APINameLoc = getArgumentNameLoc();
   SourceLoc nameLoc = getNameLoc();
-  
-  if (APINameLoc.isValid() && nameLoc.isInvalid())
-    range = APINameLoc;
-  else if (APINameLoc.isInvalid() && nameLoc.isValid())
-    range = nameLoc;
-  else
-    range = SourceRange(APINameLoc, nameLoc);
-  
-  if (range.isInvalid()) return range;
-  
+
+  SourceLoc startLoc;
+  if (APINameLoc.isValid())
+    startLoc = APINameLoc;
+  else if (nameLoc.isValid())
+    startLoc = nameLoc;
+  else {
+    startLoc = getTypeLoc().getSourceRange().Start;
+  }
+  if (startLoc.isInvalid())
+    return SourceRange();
+
   // It would be nice to extend the front of the range to show where inout is,
   // but we don't have that location info.  Extend the back of the range to the
   // location of the default argument, or the typeloc if they are valid.
   if (auto expr = getDefaultValue()) {
     auto endLoc = expr->getEndLoc();
     if (endLoc.isValid())
-      return SourceRange(range.Start, endLoc);
+      return SourceRange(startLoc, endLoc);
   }
 
   // If the typeloc has a valid location, use it to end the range.
   if (auto typeRepr = getTypeLoc().getTypeRepr()) {
     auto endLoc = typeRepr->getEndLoc();
     if (endLoc.isValid() && !isTypeLocImplicit())
-      return SourceRange(range.Start, endLoc);
+      return SourceRange(startLoc, endLoc);
   }
-  
-  // Otherwise, just return the info we have about the parameter.
-  return range;
+
+  // The name has a location we can use.
+  if (nameLoc.isValid())
+    return SourceRange(startLoc, nameLoc);
+
+  return startLoc;
 }
 
 Type ParamDecl::getVarargBaseTy(Type VarArgT) {

lib/Parse/ParseDecl.cpp

@@ -3421,15 +3421,6 @@ bool Parser::parseGetSetImpl(ParseDeclOptions Flags, ParameterList *Indices,
   // an implicit fallthrough off the end.
   if (Tok.is(tok::r_brace)) {
     diagnose(Tok, diag::computed_property_no_accessors);
-    auto *TheDecl = createAccessorFunc(VarLBLoc, nullptr, TypeLoc(), nullptr,
-                                       SourceLoc(), Flags,
-                                       AccessorKind::IsGetter,
-                                       AddressorKind::NotAddressor, this,
-                                       SourceLoc());
-
-    TheDecl->setBody(BraceStmt::create(Context, VarLBLoc, {}, Tok.getLoc()));
-    TheDecl->setInvalid();
-    Decls.push_back(TheDecl);
     return true;
   }
 

lib/Parse/ParseStmt.cpp

@@ -2017,11 +2017,10 @@ ParserResult<CatchStmt> Parser::parseStmtCatch() {
     return makeParserCodeCompletionResult<CatchStmt>();
   }
 
-  SourceLoc startOfBody = Tok.getLoc();
   auto bodyResult = parseBraceItemList(diag::expected_lbrace_after_catch);
   status |= bodyResult;
   if (bodyResult.isNull()) {
-    bodyResult = makeParserErrorResult(BraceStmt::create(Context, startOfBody,
+    bodyResult = makeParserErrorResult(BraceStmt::create(Context, PreviousLoc,
                                                          {}, PreviousLoc,
                                                          /*implicit=*/ true));
   }
@@ -2330,7 +2329,7 @@ ParserResult<Stmt> Parser::parseStmtForCStyle(SourceLoc ForLoc,
   Status |= Body;
   if (Body.isNull())
     Body = makeParserResult(
-        Body, BraceStmt::create(Context, ForLoc, {}, PreviousLoc, true));
+        Body, BraceStmt::create(Context, PreviousLoc, {}, PreviousLoc, true));
 
   return makeParserResult(
       Status,