[Sema] Enable -Wimplicit-float-conversion for integral to floating point precision loss

Issue an warning when the code tries to do an implicit int -> float
conversion, where the float type ha a narrower significant than the
float type.

The new warning is controlled by flag -Wimplicit-int-float-conversion,
under -Wimplicit-float-conversion and -Wconversion. It is also silenced
when c++11 narrowing warning is issued.

Differential Revision: https://reviews.llvm.org/D64666

llvm-svn: 367497

1 files changed, 10 insertions, 0 deletions

diff --git a/clang/test/Sema/implicit-int-float-narrowing.cpp b/clang/test/Sema/implicit-int-float-narrowing.cpp
new file mode 100644
index 00000000000..6de637e78c5
--- /dev/null
+++ b/clang/test/Sema/implicit-int-float-narrowing.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 %s -verify -Wno-conversion -Wno-c++11-narrowing -Wimplicit-int-float-conversion
+
+void testNoWarningOnNarrowing() {
+  // Test that we do not issue duplicated warnings for
+  // C++11 narrowing.
+  float a = {222222222222L}; // expected-no-diagnostics
+
+  long b = 222222222222L;
+  float c = {b}; // expected-no-diagnostics
+}