diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 37e21e8dcb9..86a17cb6a48 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -6490,6 +6490,10 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         be searched <emphasis>before</emphasis> searching any of the path items.
        </para>
 
+       <!-- To further split hairs, funcname('foo') does not use the temporary
+            schema, even when it considers typname='funcname'.  This paragraph
+            refers to function names in a loose sense, "pg_proc.proname or
+            func_name grammar production". -->
        <para>
         Likewise, the current session's temporary-table schema,
         <literal>pg_temp_<replaceable>nnn</replaceable></literal>, is always searched if it
diff --git a/src/backend/catalog/namespace.c b/src/backend/catalog/namespace.c
index 19928e9f154..ed38350d7ce 100644
--- a/src/backend/catalog/namespace.c
+++ b/src/backend/catalog/namespace.c
@@ -757,13 +757,23 @@ RelationIsVisible(Oid relid)
 
 /*
  * TypenameGetTypid
+ *		Wrapper for binary compatibility.
+ */
+Oid
+TypenameGetTypid(const char *typname)
+{
+	return TypenameGetTypidExtended(typname, true);
+}
+
+/*
+ * TypenameGetTypidExtended
  *		Try to resolve an unqualified datatype name.
  *		Returns OID if type found in search path, else InvalidOid.
  *
  * This is essentially the same as RelnameGetRelid.
  */
 Oid
-TypenameGetTypid(const char *typname)
+TypenameGetTypidExtended(const char *typname, bool temp_ok)
 {
 	Oid			typid;
 	ListCell   *l;
@@ -774,6 +784,9 @@ TypenameGetTypid(const char *typname)
 	{
 		Oid			namespaceId = lfirst_oid(l);
 
+		if (!temp_ok && namespaceId == myTempNamespace)
+			continue;			/* do not look in temp namespace */
+
 		typid = GetSysCacheOid2(TYPENAMENSP,
 								PointerGetDatum(typname),
 								ObjectIdGetDatum(namespaceId));
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 141007d5a4b..c4bed4fc058 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -1877,7 +1877,12 @@ FuncNameAsType(List *funcname)
 	Oid			result;
 	Type		typtup;
 
-	typtup = LookupTypeName(NULL, makeTypeNameFromNameList(funcname), NULL, false);
+	/*
+	 * temp_ok=false protects the <refsect1 id="sql-createfunction-security">
+	 * contract for writing SECURITY DEFINER functions safely.
+	 */
+	typtup = LookupTypeNameExtended(NULL, makeTypeNameFromNameList(funcname),
+									NULL, false, false);
 	if (typtup == NULL)
 		return InvalidOid;
 
diff --git a/src/backend/parser/parse_type.c b/src/backend/parser/parse_type.c
index d959b6122a5..a5cfa0df2b5 100644
--- a/src/backend/parser/parse_type.c
+++ b/src/backend/parser/parse_type.c
@@ -33,6 +33,18 @@ static int32 typenameTypeMod(ParseState *pstate, const TypeName *typeName,
 
 /*
  * LookupTypeName
+ *		Wrapper for typical case.
+ */
+Type
+LookupTypeName(ParseState *pstate, const TypeName *typeName,
+			   int32 *typmod_p, bool missing_ok)
+{
+	return LookupTypeNameExtended(pstate,
+								  typeName, typmod_p, true, missing_ok);
+}
+
+/*
+ * LookupTypeNameExtended
  *		Given a TypeName object, lookup the pg_type syscache entry of the type.
  *		Returns NULL if no such type can be found.  If the type is found,
  *		the typmod value represented in the TypeName struct is computed and
@@ -51,11 +63,17 @@ static int32 typenameTypeMod(ParseState *pstate, const TypeName *typeName,
  * found but is a shell, and there is typmod decoration, an error will be
  * thrown --- this is intentional.
  *
+ * If temp_ok is false, ignore types in the temporary namespace.  Pass false
+ * when the caller will decide, using goodness of fit criteria, whether the
+ * typeName is actually a type or something else.  If typeName always denotes
+ * a type (or denotes nothing), pass true.
+ *
  * pstate is only used for error location info, and may be NULL.
  */
 Type
-LookupTypeName(ParseState *pstate, const TypeName *typeName,
-			   int32 *typmod_p, bool missing_ok)
+LookupTypeNameExtended(ParseState *pstate,
+					   const TypeName *typeName, int32 *typmod_p,
+					   bool temp_ok, bool missing_ok)
 {
 	Oid			typoid;
 	HeapTuple	tup;
@@ -172,7 +190,7 @@ LookupTypeName(ParseState *pstate, const TypeName *typeName,
 		else
 		{
 			/* Unqualified type name, so search the search path */
-			typoid = TypenameGetTypid(typname);
+			typoid = TypenameGetTypidExtended(typname, temp_ok);
 		}
 
 		/* If an array reference, return the array type instead */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 74a18a146d0..364e465cbec 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9400,6 +9400,14 @@ get_coercion_expr(Node *arg, deparse_context *context,
 		if (!PRETTY_PAREN(context))
 			appendStringInfoChar(buf, ')');
 	}
+
+	/*
+	 * Never emit resulttype(arg) functional notation. A pg_proc entry could
+	 * take precedence, and a resulttype in pg_temp would require schema
+	 * qualification that format_type_with_typemod() would usually omit. We've
+	 * standardized on arg::resulttype, but CAST(arg AS resulttype) notation
+	 * would work fine.
+	 */
 	appendStringInfo(buf, "::%s",
 					 format_type_with_typemod(resulttype, resulttypmod));
 }
diff --git a/src/include/catalog/namespace.h b/src/include/catalog/namespace.h
index 0e202372d5a..17817515994 100644
--- a/src/include/catalog/namespace.h
+++ b/src/include/catalog/namespace.h
@@ -77,6 +77,7 @@ extern Oid	RelnameGetRelid(const char *relname);
 extern bool RelationIsVisible(Oid relid);
 
 extern Oid	TypenameGetTypid(const char *typname);
+extern Oid	TypenameGetTypidExtended(const char *typname, bool temp_ok);
 extern bool TypeIsVisible(Oid typid);
 
 extern FuncCandidateList FuncnameGetCandidates(List *names,
diff --git a/src/include/parser/parse_type.h b/src/include/parser/parse_type.h
index ab16737d570..74958682f23 100644
--- a/src/include/parser/parse_type.h
+++ b/src/include/parser/parse_type.h
@@ -21,6 +21,9 @@ typedef HeapTuple Type;
 
 extern Type LookupTypeName(ParseState *pstate, const TypeName *typeName,
 			   int32 *typmod_p, bool missing_ok);
+extern Type LookupTypeNameExtended(ParseState *pstate,
+								   const TypeName *typeName, int32 *typmod_p,
+								   bool temp_ok, bool missing_ok);
 extern Oid LookupTypeNameOid(ParseState *pstate, const TypeName *typeName,
 				  bool missing_ok);
 extern Type typenameType(ParseState *pstate, const TypeName *typeName,
diff --git a/src/test/regress/expected/temp.out b/src/test/regress/expected/temp.out
index 97fe478caed..410734d7dcc 100644
--- a/src/test/regress/expected/temp.out
+++ b/src/test/regress/expected/temp.out
@@ -199,6 +199,21 @@ select pg_temp.whoami();
 (1 row)
 
 drop table public.whereami;
+-- types in temp schema
+set search_path = pg_temp, public;
+create domain pg_temp.nonempty as text check (value <> '');
+-- function-syntax invocation of types matches rules for functions
+select nonempty('');
+ERROR:  function nonempty(unknown) does not exist
+LINE 1: select nonempty('');
+               ^
+HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
+select pg_temp.nonempty('');
+ERROR:  value for domain nonempty violates check constraint "nonempty_check"
+-- other syntax matches rules for tables
+select ''::nonempty;
+ERROR:  value for domain nonempty violates check constraint "nonempty_check"
+reset search_path;
 -- For partitioned temp tables, ON COMMIT actions ignore storage-less
 -- partitioned tables.
 begin;
diff --git a/src/test/regress/sql/temp.sql b/src/test/regress/sql/temp.sql
index 17366a33a91..d0367a1c1c4 100644
--- a/src/test/regress/sql/temp.sql
+++ b/src/test/regress/sql/temp.sql
@@ -152,6 +152,17 @@ select pg_temp.whoami();
 
 drop table public.whereami;
 
+-- types in temp schema
+set search_path = pg_temp, public;
+create domain pg_temp.nonempty as text check (value <> '');
+-- function-syntax invocation of types matches rules for functions
+select nonempty('');
+select pg_temp.nonempty('');
+-- other syntax matches rules for tables
+select ''::nonempty;
+
+reset search_path;
+
 -- For partitioned temp tables, ON COMMIT actions ignore storage-less
 -- partitioned tables.
 begin;