9768: Fix ast with throw in the middle of return (#2678)

* 9768: Fix ast with throw in the middle of return

```
int f(bool x)
{
    return x ? 0 : throw 0;
}
```

The `throw` part was not included in the ast, leading to an invalid
ternary operator.

* 8526: Fix ast construction for ternary operator

This tries to decide a bit more properly when ':' can be part of a
ternary operator. More precisely, there are some times when we want to
delay the construction of the ast for ':', so that it is place
accordingly to the matching '?'.

Typically, this fixes an issue with
`return val < 0 ? throw 1 : val;`,
where the ast for ':' would be constructed during as part of the
`throw`, and the ast for `?` would be invalid.

This patch is a bit of a hardcode, stating that we don't expect ':'
inside a throw, unless there is a complete ternary operator in there
(there can't be a range based for loop, a case in a switch). When we
reach ':', we know we are and the end of the `throw`.

lib/tokenlist.cpp

@@ -465,8 +465,9 @@ struct AST_state {
     bool cpp;
     int assign;
     bool inCase; // true from case to :
+    bool stopAtColon; // help to properly parse ternary operators
     const Token *functionCallEndPar;
-    explicit AST_state(bool cpp) : depth(0), inArrayAssignment(0), cpp(cpp), assign(0), inCase(false), functionCallEndPar(nullptr) {}
+    explicit AST_state(bool cpp) : depth(0), inArrayAssignment(0), cpp(cpp), assign(0), inCase(false),stopAtColon(false), functionCallEndPar(nullptr) {}
 };
 
 static Token * skipDecl(Token *tok)
@@ -762,8 +763,13 @@ static void compileTerm(Token *&tok, AST_state& state)
         if (Token::Match(tok, "return|case") || (state.cpp && tok->str() == "throw")) {
             if (tok->str() == "case")
                 state.inCase = true;
+            const bool tokIsReturn = tok->str() == "return";
+            const bool stopAtColon = state.stopAtColon;
+            state.stopAtColon=true;
             compileUnaryOp(tok, state, compileExpression);
-            state.op.pop();
+            state.stopAtColon=stopAtColon;
+            if (tokIsReturn)
+                state.op.pop();
             if (state.inCase && Token::simpleMatch(tok, ": ;")) {
                 state.inCase = false;
                 tok = tok->next();
@@ -1209,6 +1215,8 @@ static void compileAssignTernary(Token *&tok, AST_state& state)
             // http://en.cppreference.com/w/cpp/language/operator_precedence says about ternary operator:
             //       "The expression in the middle of the conditional operator (between ? and :) is parsed as if parenthesized: its precedence relative to ?: is ignored."
             // Hence, we rely on Tokenizer::prepareTernaryOpForAST() to add such parentheses where necessary.
+            const bool stopAtColon = state.stopAtColon;
+            state.stopAtColon = false;
             if (tok->strAt(1) == ":") {
                 state.op.push(nullptr);
             }
@@ -1216,12 +1224,15 @@ static void compileAssignTernary(Token *&tok, AST_state& state)
             state.assign = 0;
             compileBinOp(tok, state, compileAssignTernary);
             state.assign = assign;
+            state.stopAtColon = stopAtColon;
         } else if (tok->str() == ":") {
             if (state.depth == 1U && state.inCase) {
                 state.inCase = false;
                 tok = tok->next();
                 break;
             }
+            if (state.stopAtColon)
+                break;
             if (state.assign > 0)
                 break;
             compileBinOp(tok, state, compileAssignTernary);

test/testtokenize.cpp

@@ -7484,6 +7484,10 @@ private:
         ASSERT_EQUALS("fabc,de,:?=", testAst("f = (a ? b, c : (d, e));"));
         ASSERT_EQUALS("ab35,4:?foo(:?return", testAst("return (a ? b ? (3,5) : 4 : foo());"));
         ASSERT_EQUALS("check(result_type00,{invalid:?return", testAst("return check() ? result_type {0, 0} : invalid;"));
+        ASSERT_EQUALS("x01:?return", testAst("return x ? 0 : 1;"));
+        ASSERT_EQUALS("x00throw:?return", testAst("return x ? 0 : throw 0;")); // #9768
+        ASSERT_EQUALS("val0<1throwval:?return", testAst("return val < 0 ? throw 1 : val;")); // #8526
+        ASSERT_EQUALS("ix0<00throw:?=", testAst("int i = x < 0 ? 0 : throw 0;"));
 
         ASSERT_EQUALS("a\"\"=", testAst("a=\"\""));
         ASSERT_EQUALS("a\'\'=", testAst("a=\'\'"));
@@ -7927,6 +7931,7 @@ private:
         ASSERT_EQUALS("0case", testAst("case 0:"));
         ASSERT_EQUALS("12+case", testAst("case 1+2:"));
         ASSERT_EQUALS("xyz:?case", testAst("case (x?y:z):"));
+        ASSERT_EQUALS("switchx( 1case y++ 2case", testAst("switch(x){case 1:{++y;break;case 2:break;}}"));
     }
 
     void astrefqualifier() {