diff --git a/dom/base/Selection.h b/dom/base/Selection.h
index bee0af78c760..9714b0d43579 100644
--- a/dom/base/Selection.h
+++ b/dom/base/Selection.h
@@ -1228,28 +1228,28 @@ class MOZ_RAII AutoHideSelectionChanges final {
 
 }  // namespace dom
 
-inline bool IsValidRawSelectionType(RawSelectionType aRawSelectionType) {
+constexpr bool IsValidRawSelectionType(RawSelectionType aRawSelectionType) {
   return aRawSelectionType >= nsISelectionController::SELECTION_NONE &&
          aRawSelectionType <= nsISelectionController::SELECTION_URLSTRIKEOUT;
 }
 
-inline SelectionType ToSelectionType(RawSelectionType aRawSelectionType) {
+constexpr SelectionType ToSelectionType(RawSelectionType aRawSelectionType) {
   if (!IsValidRawSelectionType(aRawSelectionType)) {
     return SelectionType::eInvalid;
   }
   return static_cast<SelectionType>(aRawSelectionType);
 }
 
-inline RawSelectionType ToRawSelectionType(SelectionType aSelectionType) {
+constexpr RawSelectionType ToRawSelectionType(SelectionType aSelectionType) {
   MOZ_ASSERT(aSelectionType != SelectionType::eInvalid);
   return static_cast<RawSelectionType>(aSelectionType);
 }
 
-inline RawSelectionType ToRawSelectionType(TextRangeType aTextRangeType) {
+constexpr RawSelectionType ToRawSelectionType(TextRangeType aTextRangeType) {
   return ToRawSelectionType(ToSelectionType(aTextRangeType));
 }
 
-inline SelectionTypeMask ToSelectionTypeMask(SelectionType aSelectionType) {
+constexpr SelectionTypeMask ToSelectionTypeMask(SelectionType aSelectionType) {
   MOZ_ASSERT(aSelectionType != SelectionType::eInvalid);
   return aSelectionType == SelectionType::eNone
              ? 0
diff --git a/dom/base/nsISelectionController.idl b/dom/base/nsISelectionController.idl
index eaaa2d02bca0..29d1875384ca 100644
--- a/dom/base/nsISelectionController.idl
+++ b/dom/base/nsISelectionController.idl
@@ -339,10 +339,10 @@ static const SelectionType kPresentSelectionTypes[] = {
 };
 
 // Please include mozilla/dom/Selection.h for the following APIs.
-inline bool IsValidRawSelectionType(RawSelectionType aRawSelectionType);
-inline SelectionType ToSelectionType(RawSelectionType aRawSelectionType);
-inline RawSelectionType ToRawSelectionType(SelectionType aSelectionType);
-inline SelectionTypeMask ToSelectionTypeMask(SelectionType aSelectionType);
+constexpr bool IsValidRawSelectionType(RawSelectionType aRawSelectionType);
+constexpr SelectionType ToSelectionType(RawSelectionType aRawSelectionType);
+constexpr RawSelectionType ToRawSelectionType(SelectionType aSelectionType);
+constexpr SelectionTypeMask ToSelectionTypeMask(SelectionType aSelectionType);
 
 } // namespace mozilla
 %}
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index e65dc70f56aa..5412fe04648b 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -5472,7 +5472,7 @@ gfxFloat nsTextFrame::ComputeDescentLimitForSelectionUnderline(
 }
 
 // Make sure this stays in sync with DrawSelectionDecorations below
-static const SelectionTypeMask kSelectionTypesWithDecorations =
+static constexpr SelectionTypeMask kSelectionTypesWithDecorations =
     ToSelectionTypeMask(SelectionType::eSpellCheck) |
     ToSelectionTypeMask(SelectionType::eURLStrikeout) |
     ToSelectionTypeMask(SelectionType::eIMERawClause) |
diff --git a/widget/TextRange.h b/widget/TextRange.h
index 2ad41a6bc618..eed62b7c387a 100644
--- a/widget/TextRange.h
+++ b/widget/TextRange.h
@@ -137,12 +137,6 @@ enum class TextRangeType : RawTextRangeType {
   eSelectedClause = nsITextInputProcessor::ATTR_SELECTED_CLAUSE
 };
 
-bool IsValidRawTextRangeValue(RawTextRangeType aRawTextRangeValue);
-RawTextRangeType ToRawTextRangeType(TextRangeType aTextRangeType);
-TextRangeType ToTextRangeType(RawTextRangeType aRawTextRangeType);
-const char* ToChar(TextRangeType aTextRangeType);
-SelectionType ToSelectionType(TextRangeType aTextRangeType);
-
 struct TextRange {
   TextRange()
       : mStartOffset(0),
@@ -178,6 +172,64 @@ struct TextRange {
   }
 };
 
+constexpr bool IsValidRawTextRangeValue(RawTextRangeType aRawTextRangeType) {
+  switch (static_cast<TextRangeType>(aRawTextRangeType)) {
+    case TextRangeType::eUninitialized:
+    case TextRangeType::eCaret:
+    case TextRangeType::eRawClause:
+    case TextRangeType::eSelectedRawClause:
+    case TextRangeType::eConvertedClause:
+    case TextRangeType::eSelectedClause:
+      return true;
+    default:
+      return false;
+  }
+}
+
+constexpr RawTextRangeType ToRawTextRangeType(TextRangeType aTextRangeType) {
+  return static_cast<RawTextRangeType>(aTextRangeType);
+}
+
+constexpr TextRangeType ToTextRangeType(RawTextRangeType aRawTextRangeType) {
+  MOZ_ASSERT(IsValidRawTextRangeValue(aRawTextRangeType));
+  return static_cast<TextRangeType>(aRawTextRangeType);
+}
+
+constexpr const char* ToChar(TextRangeType aTextRangeType) {
+  switch (aTextRangeType) {
+    case TextRangeType::eUninitialized:
+      return "TextRangeType::eUninitialized";
+    case TextRangeType::eCaret:
+      return "TextRangeType::eCaret";
+    case TextRangeType::eRawClause:
+      return "TextRangeType::eRawClause";
+    case TextRangeType::eSelectedRawClause:
+      return "TextRangeType::eSelectedRawClause";
+    case TextRangeType::eConvertedClause:
+      return "TextRangeType::eConvertedClause";
+    case TextRangeType::eSelectedClause:
+      return "TextRangeType::eSelectedClause";
+    default:
+      return "Invalid TextRangeType";
+  }
+}
+
+constexpr SelectionType ToSelectionType(TextRangeType aTextRangeType) {
+  switch (aTextRangeType) {
+    case TextRangeType::eRawClause:
+      return SelectionType::eIMERawClause;
+    case TextRangeType::eSelectedRawClause:
+      return SelectionType::eIMESelectedRawClause;
+    case TextRangeType::eConvertedClause:
+      return SelectionType::eIMEConvertedClause;
+    case TextRangeType::eSelectedClause:
+      return SelectionType::eIMESelectedClause;
+    default:
+      MOZ_CRASH("TextRangeType is invalid");
+      return SelectionType::eNormal;
+  }
+}
+
 /******************************************************************************
  * mozilla::TextRangeArray
  ******************************************************************************/
diff --git a/widget/WidgetEventImpl.cpp b/widget/WidgetEventImpl.cpp
index 0e761d371614..44b5a3d67297 100644
--- a/widget/WidgetEventImpl.cpp
+++ b/widget/WidgetEventImpl.cpp
@@ -256,64 +256,6 @@ const nsCString GetDOMKeyCodeName(uint32_t aKeyCode) {
   }
 }
 
-bool IsValidRawTextRangeValue(RawTextRangeType aRawTextRangeType) {
-  switch (static_cast<TextRangeType>(aRawTextRangeType)) {
-    case TextRangeType::eUninitialized:
-    case TextRangeType::eCaret:
-    case TextRangeType::eRawClause:
-    case TextRangeType::eSelectedRawClause:
-    case TextRangeType::eConvertedClause:
-    case TextRangeType::eSelectedClause:
-      return true;
-    default:
-      return false;
-  }
-}
-
-RawTextRangeType ToRawTextRangeType(TextRangeType aTextRangeType) {
-  return static_cast<RawTextRangeType>(aTextRangeType);
-}
-
-TextRangeType ToTextRangeType(RawTextRangeType aRawTextRangeType) {
-  MOZ_ASSERT(IsValidRawTextRangeValue(aRawTextRangeType));
-  return static_cast<TextRangeType>(aRawTextRangeType);
-}
-
-const char* ToChar(TextRangeType aTextRangeType) {
-  switch (aTextRangeType) {
-    case TextRangeType::eUninitialized:
-      return "TextRangeType::eUninitialized";
-    case TextRangeType::eCaret:
-      return "TextRangeType::eCaret";
-    case TextRangeType::eRawClause:
-      return "TextRangeType::eRawClause";
-    case TextRangeType::eSelectedRawClause:
-      return "TextRangeType::eSelectedRawClause";
-    case TextRangeType::eConvertedClause:
-      return "TextRangeType::eConvertedClause";
-    case TextRangeType::eSelectedClause:
-      return "TextRangeType::eSelectedClause";
-    default:
-      return "Invalid TextRangeType";
-  }
-}
-
-SelectionType ToSelectionType(TextRangeType aTextRangeType) {
-  switch (aTextRangeType) {
-    case TextRangeType::eRawClause:
-      return SelectionType::eIMERawClause;
-    case TextRangeType::eSelectedRawClause:
-      return SelectionType::eIMESelectedRawClause;
-    case TextRangeType::eConvertedClause:
-      return SelectionType::eIMEConvertedClause;
-    case TextRangeType::eSelectedClause:
-      return SelectionType::eIMESelectedClause;
-    default:
-      MOZ_CRASH("TextRangeType is invalid");
-      return SelectionType::eNormal;
-  }
-}
-
 /******************************************************************************
  * non class method implementation
  ******************************************************************************/