Re-commit r273548, reverted in r273589, with a fix to not produce

-Wfor-loop-analysis warnings for a for-loop with a condition variable. In such
a case, the loop condition variable is modified on each iteration of the loop
by definition.

Original commit message:

Rearrange condition handling so that semantic checks on a condition variable
are performed before the other substatements of the construct are parsed,
rather than deferring them until the end. This allows better error recovery
from semantic errors in the condition, improves diagnostic order, and is a
prerequisite for C++17 constexpr if.

llvm-svn: 273600

1 files changed, 34 insertions, 46 deletions

diff --git a/clang/lib/Parse/ParseStmt.cpp b/clang/lib/Parse/ParseStmt.cpp
index 8173d09cbbe..c849554238e 100644
--- a/clang/lib/Parse/ParseStmt.cpp
+++ b/clang/lib/Parse/ParseStmt.cpp
@@ -1052,29 +1052,28 @@ StmtResult Parser::ParseCompoundStatementBody(bool isStmtExpr) {
 /// should try to recover harder.  It returns false if the condition is
 /// successfully parsed.  Note that a successful parse can still have semantic
 /// errors in the condition.
-bool Parser::ParseParenExprOrCondition(ExprResult &ExprResult,
-                                       Decl *&DeclResult,
+bool Parser::ParseParenExprOrCondition(Sema::ConditionResult &Cond,
                                        SourceLocation Loc,
-                                       bool ConvertToBoolean) {
+                                       Sema::ConditionKind CK) {
   BalancedDelimiterTracker T(*this, tok::l_paren);
   T.consumeOpen();
 
   if (getLangOpts().CPlusPlus)
-    ParseCXXCondition(ExprResult, DeclResult, Loc, ConvertToBoolean);
+    Cond = ParseCXXCondition(Loc, CK);
   else {
-    ExprResult = ParseExpression();
-    DeclResult = nullptr;
+    ExprResult CondExpr = ParseExpression();
 
     // If required, convert to a boolean value.
-    if (!ExprResult.isInvalid() && ConvertToBoolean)
-      ExprResult
-        = Actions.ActOnBooleanCondition(getCurScope(), Loc, ExprResult.get());
+    if (CondExpr.isInvalid())
+      Cond = Sema::ConditionError();
+    else
+      Cond = Actions.ActOnCondition(getCurScope(), Loc, CondExpr.get(), CK);
   }
 
   // If the parser was confused by the condition and we don't have a ')', try to
   // recover by skipping ahead to a semi and bailing out.  If condexp is
   // semantically invalid but we have well formed code, keep going.
-  if (ExprResult.isInvalid() && !DeclResult && Tok.isNot(tok::r_paren)) {
+  if (Cond.isInvalid() && Tok.isNot(tok::r_paren)) {
     SkipUntil(tok::semi);
     // Skipping may have stopped if it found the containing ')'.  If so, we can
     // continue parsing the if statement.
@@ -1132,13 +1131,10 @@ StmtResult Parser::ParseIfStatement(SourceLocation *TrailingElseLoc) {
   ParseScope IfScope(this, Scope::DeclScope | Scope::ControlScope, C99orCXX);
 
   // Parse the condition.
-  ExprResult CondExp;
-  Decl *CondVar = nullptr;
-  if (ParseParenExprOrCondition(CondExp, CondVar, IfLoc, true))
+  Sema::ConditionResult Cond;
+  if (ParseParenExprOrCondition(Cond, IfLoc, Sema::ConditionKind::Boolean))
     return StmtError();
 
-  FullExprArg FullCondExp(Actions.MakeFullExpr(CondExp.get(), IfLoc));
-
   // C99 6.8.4p3 - In C99, the body of the if statement is a scope, even if
   // there is no compound stmt.  C90 does not have this clause.  We only do this
   // if the body isn't a compound statement to avoid push/pop in common cases.
@@ -1221,8 +1217,8 @@ StmtResult Parser::ParseIfStatement(SourceLocation *TrailingElseLoc) {
   if (ElseStmt.isInvalid())
     ElseStmt = Actions.ActOnNullStmt(ElseStmtLoc);
 
-  return Actions.ActOnIfStmt(IfLoc, FullCondExp, CondVar, ThenStmt.get(),
-                             ElseLoc, ElseStmt.get());
+  return Actions.ActOnIfStmt(IfLoc, Cond, ThenStmt.get(), ElseLoc,
+                             ElseStmt.get());
 }
 
 /// ParseSwitchStatement
@@ -1259,13 +1255,11 @@ StmtResult Parser::ParseSwitchStatement(SourceLocation *TrailingElseLoc) {
   ParseScope SwitchScope(this, ScopeFlags);
 
   // Parse the condition.
-  ExprResult Cond;
-  Decl *CondVar = nullptr;
-  if (ParseParenExprOrCondition(Cond, CondVar, SwitchLoc, false))
+  Sema::ConditionResult Cond;
+  if (ParseParenExprOrCondition(Cond, SwitchLoc, Sema::ConditionKind::Switch))
     return StmtError();
 
-  StmtResult Switch
-    = Actions.ActOnStartOfSwitchStmt(SwitchLoc, Cond.get(), CondVar);
+  StmtResult Switch = Actions.ActOnStartOfSwitchStmt(SwitchLoc, Cond);
 
   if (Switch.isInvalid()) {
     // Skip the switch body.
@@ -1347,13 +1341,10 @@ StmtResult Parser::ParseWhileStatement(SourceLocation *TrailingElseLoc) {
   ParseScope WhileScope(this, ScopeFlags);
 
   // Parse the condition.
-  ExprResult Cond;
-  Decl *CondVar = nullptr;
-  if (ParseParenExprOrCondition(Cond, CondVar, WhileLoc, true))
+  Sema::ConditionResult Cond;
+  if (ParseParenExprOrCondition(Cond, WhileLoc, Sema::ConditionKind::Boolean))
     return StmtError();
 
-  FullExprArg FullCond(Actions.MakeFullExpr(Cond.get(), WhileLoc));
-
   // C99 6.8.5p5 - In C99, the body of the while statement is a scope, even if
   // there is no compound stmt.  C90 does not have this clause.  We only do this
   // if the body isn't a compound statement to avoid push/pop in common cases.
@@ -1374,10 +1365,10 @@ StmtResult Parser::ParseWhileStatement(SourceLocation *TrailingElseLoc) {
   InnerScope.Exit();
   WhileScope.Exit();
 
-  if ((Cond.isInvalid() && !CondVar) || Body.isInvalid())
+  if (Cond.isInvalid() || Body.isInvalid())
     return StmtError();
 
-  return Actions.ActOnWhileStmt(WhileLoc, FullCond, CondVar, Body.get());
+  return Actions.ActOnWhileStmt(WhileLoc, Cond, Body.get());
 }
 
 /// ParseDoStatement
@@ -1535,12 +1526,10 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
 
   bool ForEach = false, ForRange = false;
   StmtResult FirstPart;
-  bool SecondPartIsInvalid = false;
-  FullExprArg SecondPart(Actions);
+  Sema::ConditionResult SecondPart;
   ExprResult Collection;
   ForRangeInit ForRangeInit;
   FullExprArg ThirdPart(Actions);
-  Decl *SecondVar = nullptr;
 
   if (Tok.is(tok::code_completion)) {
     Actions.CodeCompleteOrdinaryName(getCurScope(),
@@ -1645,7 +1634,7 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
       Diag(Tok, diag::err_for_range_expected_decl)
         << FirstPart.get()->getSourceRange();
       SkipUntil(tok::r_paren, StopBeforeMatch);
-      SecondPartIsInvalid = true;
+      SecondPart = Sema::ConditionError();
     } else {
       if (!Value.isInvalid()) {
         Diag(Tok, diag::err_expected_semi_for);
@@ -1660,29 +1649,28 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
 
   // Parse the second part of the for specifier.
   getCurScope()->AddFlags(Scope::BreakScope | Scope::ContinueScope);
-  if (!ForEach && !ForRange) {
-    assert(!SecondPart.get() && "Shouldn't have a second expression yet.");
+  if (!ForEach && !ForRange && !SecondPart.isInvalid()) {
     // Parse the second part of the for specifier.
     if (Tok.is(tok::semi)) {  // for (...;;
       // no second part.
     } else if (Tok.is(tok::r_paren)) {
       // missing both semicolons.
     } else {
-      ExprResult Second;
       if (getLangOpts().CPlusPlus)
-        ParseCXXCondition(Second, SecondVar, ForLoc, true);
+        SecondPart = ParseCXXCondition(ForLoc, Sema::ConditionKind::Boolean);
       else {
-        Second = ParseExpression();
-        if (!Second.isInvalid())
-          Second = Actions.ActOnBooleanCondition(getCurScope(), ForLoc,
-                                                 Second.get());
+        ExprResult SecondExpr = ParseExpression();
+        if (SecondExpr.isInvalid())
+          SecondPart = Sema::ConditionError();
+        else
+          SecondPart =
+              Actions.ActOnCondition(getCurScope(), ForLoc, SecondExpr.get(),
+                                     Sema::ConditionKind::Boolean);
       }
-      SecondPartIsInvalid = Second.isInvalid();
-      SecondPart = Actions.MakeFullExpr(Second.get(), ForLoc);
     }
 
     if (Tok.isNot(tok::semi)) {
-      if (!SecondPartIsInvalid || SecondVar)
+      if (!SecondPart.isInvalid())
         Diag(Tok, diag::err_expected_semi_for);
       else
         // Skip until semicolon or rparen, don't consume it.
@@ -1781,8 +1769,8 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc) {
     return Actions.FinishCXXForRangeStmt(ForRangeStmt.get(), Body.get());
 
   return Actions.ActOnForStmt(ForLoc, T.getOpenLocation(), FirstPart.get(),
-                              SecondPart, SecondVar, ThirdPart,
-                              T.getCloseLocation(), Body.get());
+                              SecondPart, ThirdPart, T.getCloseLocation(),
+                              Body.get());
 }
 
 /// ParseGotoStatement