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+An `if` expression is missing an `else` block.
+
+Erroneous code example:
+
+```compile_fail,E0317
+let x = 5;
+let a = if x == 5 {
+    1
+};
+```
+
+This error occurs when an `if` expression without an `else` block is used in a
+context where a type other than `()` is expected. In the previous code example,
+the `let` expression was expecting a value but since there was no `else`, no
+value was returned.
+
+An `if` expression without an `else` block has the type `()`, so this is a type
+error. To resolve it, add an `else` block having the same type as the `if`
+block.
+
+So to fix the previous code example:
+
+```
+let x = 5;
+let a = if x == 5 {
+    1
+} else {
+    2
+};
+```