Account for collation when coercing the output of a SQL function.

Commit 913bbd88d overlooked that the result of coerce_to_target_type
might need collation fixups.  Per report from Andreas Joseph Krogh.

Discussion: https://postgr.es/m/VisenaEmail.72.37d08ec2b8cb8fb5.17179940cd3@tc7-visena

src/backend/executor/functions.c

@@ -24,6 +24,7 @@
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parse_coerce.h"
+#include "parser/parse_collate.h"
 #include "parser/parse_func.h"
 #include "storage/proc.h"
 #include "tcop/utility.h"
@@ -1989,6 +1990,7 @@ coerce_fn_result_column(TargetEntry *src_tle,
 											-1);
 		if (cast_result == NULL)
 			return false;
+		assign_expr_collations(NULL, cast_result);
 		src_tle->expr = (Expr *) cast_result;
 		/* Make a Var referencing the possibly-modified TLE */
 		new_tle_expr = (Expr *) makeVarFromTargetEntry(1, src_tle);
@@ -2007,6 +2009,7 @@ coerce_fn_result_column(TargetEntry *src_tle,
 											-1);
 		if (cast_result == NULL)
 			return false;
+		assign_expr_collations(NULL, cast_result);
 		/* Did the coercion actually do anything? */
 		if (cast_result != (Node *) var)
 			*upper_tlist_nontrivial = true;

src/test/regress/expected/collate.out

@@ -536,6 +536,18 @@ SELECT a, CAST(b AS varchar) FROM collate_test2 ORDER BY 2;
  3 | bbc
 (4 rows)
 
+-- result of a SQL function
+CREATE FUNCTION vc (text) RETURNS text LANGUAGE sql
+    AS 'select $1::varchar';
+SELECT a, b FROM collate_test1 ORDER BY a, vc(b);
+ a |  b  
+---+-----
+ 1 | abc
+ 2 | Abc
+ 3 | bbc
+ 4 | ABD
+(4 rows)
+
 -- polymorphism
 SELECT * FROM unnest((SELECT array_agg(b ORDER BY b) FROM collate_test1)) ORDER BY 1;
  unnest 
@@ -682,7 +694,7 @@ SELECT collation for ((SELECT b FROM collate_test1 LIMIT 1));
 -- must get rid of them.
 --
 DROP SCHEMA collate_tests CASCADE;
-NOTICE:  drop cascades to 17 other objects
+NOTICE:  drop cascades to 18 other objects
 DETAIL:  drop cascades to table collate_test1
 drop cascades to table collate_test_like
 drop cascades to table collate_test2
@@ -694,6 +706,7 @@ drop cascades to view collview1
 drop cascades to view collview2
 drop cascades to view collview3
 drop cascades to type testdomain
+drop cascades to function vc(text)
 drop cascades to function dup(anyelement)
 drop cascades to table collate_test20
 drop cascades to table collate_test21

src/test/regress/sql/collate.sql

@@ -177,6 +177,14 @@ SELECT a, CAST(b AS varchar) FROM collate_test1 ORDER BY 2;
 SELECT a, CAST(b AS varchar) FROM collate_test2 ORDER BY 2;
 
 
+-- result of a SQL function
+
+CREATE FUNCTION vc (text) RETURNS text LANGUAGE sql
+    AS 'select $1::varchar';
+
+SELECT a, b FROM collate_test1 ORDER BY a, vc(b);
+
+
 -- polymorphism
 
 SELECT * FROM unnest((SELECT array_agg(b ORDER BY b) FROM collate_test1)) ORDER BY 1;