From 28a7bb63ec5ae59ddbd0c22fea3bba86f760fbcb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Marjam=C3=A4ki?= <daniel.marjamaki@gmail.com>
Date: Sun, 25 Apr 2021 14:37:27 +0200
Subject: [PATCH] Parser; simplify (break out) init expression from
 if/switch/range-for

---
 lib/tokenize.cpp      | 62 +++++++++++++++++++++++++++++++++++++++++++
 lib/tokenize.h        |  3 +++
 test/testtokenize.cpp | 41 ++++++++++++++++++++++------
 3 files changed, 98 insertions(+), 8 deletions(-)

diff --git a/lib/tokenize.cpp b/lib/tokenize.cpp
index f7a823900..3c97405ae 100644
--- a/lib/tokenize.cpp
+++ b/lib/tokenize.cpp
@@ -5143,6 +5143,8 @@ bool Tokenizer::simplifyTokenList1(const char FileName[])
 
     elseif();
 
+    simplifyIfSwitchForInit();
+
     simplifyOverloadedOperators();
 
     validate();
@@ -8593,6 +8595,66 @@ void Tokenizer::elseif()
 }
 
 
+void Tokenizer::simplifyIfSwitchForInit()
+{
+    if (!isCPP() || mSettings->standards.cpp < Standards::CPP17)
+        return;
+
+    const bool forInit = (mSettings->standards.cpp >= Standards::CPP20);
+
+    for (Token *tok = list.front(); tok; tok = tok->next()) {
+        if (!Token::Match(tok, "if|switch|for ("))
+            continue;
+
+        Token *semicolon = tok->tokAt(2);
+        while (!Token::Match(semicolon, "[;)]")) {
+            if (semicolon->str() == "(")
+                semicolon = semicolon->link();
+            semicolon = semicolon->next();
+        }
+        if (semicolon->str() != ";")
+            continue;
+
+        if (tok->str() ==  "for") {
+            if (!forInit)
+                continue;
+
+            // Is it a for range..
+            const Token *tok2 = semicolon->next();
+            bool rangeFor = false;
+            while (!Token::Match(tok2, "[;)]")) {
+                if (tok2->str() == "(")
+                    tok2 = tok2->link();
+                else if (!rangeFor && tok2->str() == "?")
+                    break;
+                else if (tok2->str() == ":")
+                    rangeFor = true;
+                tok2 = tok2->next();
+            }
+            if (!rangeFor || tok2->str() != ")")
+                continue;
+        }
+
+        Token *endpar = tok->linkAt(1);
+        if (!Token::simpleMatch(endpar, ") {"))
+            continue;
+
+        Token *endscope = endpar->linkAt(1);
+        if (Token::simpleMatch(endscope, "} else {"))
+            endscope = endscope->linkAt(2);
+
+        // Simplify, the initialization expression is broken out..
+        semicolon->insertToken(tok->str());
+        semicolon->next()->insertToken("(");
+        Token::createMutualLinks(semicolon->next()->next(), endpar);
+        tok->deleteNext();
+        tok->str("{");
+        endscope->insertToken("}");
+        Token::createMutualLinks(tok, endscope->next());
+    }
+}
+
+
 bool Tokenizer::simplifyRedundantParentheses()
 {
     bool ret = false;
diff --git a/lib/tokenize.h b/lib/tokenize.h
index a11e113c7..da4861b1b 100644
--- a/lib/tokenize.h
+++ b/lib/tokenize.h
@@ -449,6 +449,9 @@ public:
     /** Simplify "if else" */
     void elseif();
 
+    /** Simplify C++17/C++20 if/switch/for initialization expression */
+    void simplifyIfSwitchForInit();
+
     /** Simplify conditions
      * @return true if something is modified
      *         false if nothing is done.
diff --git a/test/testtokenize.cpp b/test/testtokenize.cpp
index db8519f62..e7d8dc325 100644
--- a/test/testtokenize.cpp
+++ b/test/testtokenize.cpp
@@ -281,7 +281,6 @@ private:
         TEST_CASE(bitfields14); // ticket #4561 (segfault for 'class a { signals: };')
         TEST_CASE(bitfields15); // ticket #7747 (enum Foo {A,B}:4;)
         TEST_CASE(bitfields16); // Save bitfield bit count
-        TEST_CASE(bitfields17); // for (A; b:c);
 
         TEST_CASE(simplifyNamespaceStd);
 
@@ -422,6 +421,11 @@ private:
         TEST_CASE(simplifyCoroutines);
 
         TEST_CASE(simplifySpaceshipOperator);
+
+        TEST_CASE(simplifyIfSwitchForInit1);
+        TEST_CASE(simplifyIfSwitchForInit2);
+        TEST_CASE(simplifyIfSwitchForInit3);
+        TEST_CASE(simplifyIfSwitchForInit4);
     }
 
     std::string tokenizeAndStringify(const char code[], bool expand = true, Settings::PlatformType platform = Settings::Native, const char* filename = "test.cpp", bool cpp11 = true) {
@@ -3953,13 +3957,6 @@ private:
         ASSERT_EQUALS(1, x->bits());
     }
 
-    void bitfields17() {
-        Settings settings;
-        settings.standards.cpp = Standards::CPP20;
-        const char code[] = "void f() { for (a;b:c) {} }";
-        ASSERT_EQUALS("void f ( ) { for ( a ; b : c ) { } }", tokenizeAndStringify(code, settings));
-    }
-
     void simplifyNamespaceStd() {
         const char *code, *expected;
 
@@ -6556,6 +6553,34 @@ private:
 
         ASSERT_EQUALS("; x <=> y ;", tokenizeAndStringify(";x<=>y;", settings));
     }
+
+    void simplifyIfSwitchForInit1() {
+        Settings settings;
+        settings.standards.cpp = Standards::CPP17;
+        const char code[] = "void f() { if (a;b) {} }";
+        ASSERT_EQUALS("void f ( ) { { a ; if ( b ) { } } }", tokenizeAndStringify(code, settings));
+    }
+
+    void simplifyIfSwitchForInit2() {
+        Settings settings;
+        settings.standards.cpp = Standards::CPP20;
+        const char code[] = "void f() { if (a;b) {} else {} }";
+        ASSERT_EQUALS("void f ( ) { { a ; if ( b ) { } else { } } }", tokenizeAndStringify(code, settings));
+    }
+
+    void simplifyIfSwitchForInit3() {
+        Settings settings;
+        settings.standards.cpp = Standards::CPP20;
+        const char code[] = "void f() { switch (a;b) {} }";
+        ASSERT_EQUALS("void f ( ) { { a ; switch ( b ) { } } }", tokenizeAndStringify(code, settings));
+    }
+
+    void simplifyIfSwitchForInit4() {
+        Settings settings;
+        settings.standards.cpp = Standards::CPP20;
+        const char code[] = "void f() { for (a;b:c) {} }";
+        ASSERT_EQUALS("void f ( ) { { a ; for ( b : c ) { } } }", tokenizeAndStringify(code, settings));
+    }
 };
 
 REGISTER_TEST(TestTokenizer)