[Support] Avoid setting minor/subminor/build in VersionTuple::withMajorReplaced (llvm#139318)

The expectation of this API is that it only changes the major version of
a preexisting version tuple. However, it was adding 0's, which caused
unintended changes in serialization or printing.

Instead, check for the existence of the non-major parts of the tuple.

(cherry picked from commit 12e6622)

Author: cyndyishida

clang/test/Driver/xros-driver.c

@@ -30,8 +30,8 @@
 // LINK: "-platform_version" "xros" "1.0.0" "1.0.0"
 // LINK-SIM: "-platform_version" "xros-simulator" "1.0.0" "1.0.0"
 
-// OBJC-RUNTIME: "-fobjc-runtime=ios-17.0.0.0"
-// OBJC-RUNTIME2: "-fobjc-runtime=ios-18.0.0.0"
+// OBJC-RUNTIME: "-fobjc-runtime=ios-17.0.0"
+// OBJC-RUNTIME2: "-fobjc-runtime=ios-18.0.0"
 // ARC-NOT: error:
 
 // SSP_ON: "-stack-protector" "1"

llvm/include/llvm/Support/VersionTuple.h

@@ -103,9 +103,7 @@ class VersionTuple {
 
   /// Return a version tuple that contains a different major version but
   /// everything else is the same.
-  VersionTuple withMajorReplaced(unsigned NewMajor) const {
-    return VersionTuple(NewMajor, Minor, Subminor, Build);
-  }
+  VersionTuple withMajorReplaced(unsigned NewMajor) const;
 
   /// Return a version tuple that contains only components that are non-zero.
   VersionTuple normalize() const {

llvm/lib/Support/VersionTuple.cpp

@@ -108,3 +108,13 @@ bool VersionTuple::tryParse(StringRef input) {
   *this = VersionTuple(major, minor, micro, build);
   return false;
 }
+
+VersionTuple VersionTuple::withMajorReplaced(unsigned NewMajor) const {
+  if (HasBuild)
+    return VersionTuple(NewMajor, Minor, Subminor, Build);
+  if (HasSubminor)
+    return VersionTuple(NewMajor, Minor, Subminor);
+  if (HasMinor)
+    return VersionTuple(NewMajor, Minor);
+  return VersionTuple(NewMajor);
+}

llvm/unittests/Support/VersionTupleTest.cpp

@@ -47,3 +47,33 @@ TEST(VersionTuple, tryParse) {
   EXPECT_TRUE(VT.tryParse("1 "));
   EXPECT_TRUE(VT.tryParse("."));
 }
+
+TEST(VersionTuple, withMajorReplaced) {
+  VersionTuple VT(2);
+  VersionTuple ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_FALSE(ReplacedVersion.getMinor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7), ReplacedVersion);
+
+  VT = VersionTuple(100, 1);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 1), ReplacedVersion);
+
+  VT = VersionTuple(101, 11, 12);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_FALSE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 11, 12), ReplacedVersion);
+
+  VT = VersionTuple(101, 11, 12, 2);
+  ReplacedVersion = VT.withMajorReplaced(7);
+  EXPECT_TRUE(ReplacedVersion.getMinor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getSubminor().has_value());
+  EXPECT_TRUE(ReplacedVersion.getBuild().has_value());
+  EXPECT_EQ(VersionTuple(7, 11, 12, 2), ReplacedVersion);
+}