Merge #11112: [developer-notes] By default, declare single-argument constructors "explicit"

f1708ef89 Add recommendation: By default, declare single-argument constructors `explicit` (practicalswift)

Pull request description:

  This is a follow-up to the now merged #10969.

  Add recommendation:

  > By default, declare single-argument constructors `explicit`.
  >
  > - *Rationale*: This is a precaution to avoid unintended conversions that might arise when single-argument constructors are used as implicit conversion functions.
  >

Tree-SHA512: 1ceb1008a7863ebd0f09ba9c06b4e28b3b03265d7381f9d0c8bd4be1663d5d0392de0ecd811027aa27c0d962723674b245b3c165a437942a776f3525db39d36b

doc/developer-notes.md

@@ -344,6 +344,12 @@ C++ data structures
   - *Rationale*: Ensure determinism by avoiding accidental use of uninitialized
     values. Also, static analyzers balk about this.
 
+- By default, declare single-argument constructors `explicit`.
+
+  - *Rationale*: This is a precaution to avoid unintended conversions that might
+    arise when single-argument constructors are used as implicit conversion
+    functions.
+
 - Use explicitly signed or unsigned `char`s, or even better `uint8_t` and
   `int8_t`. Do not use bare `char` unless it is to pass to a third-party API.
   This type can be signed or unsigned depending on the architecture, which can

src/test/addrman_tests.cpp

@@ -15,7 +15,7 @@ class CAddrManTest : public CAddrMan
     uint64_t state;
 
 public:
-    CAddrManTest(bool makeDeterministic = true)
+    explicit CAddrManTest(bool makeDeterministic = true)
     {
         state = 1;