Improve coverage of utils/float.h

check_float4_val() checks after underflow and overflow of values
converted from float8 to float4, but there has never been any regression
tests for that.  This brings the coverage of float.h to 100%.

Author: Movead Li
Discussion: https://postgr.es/m/20190822174636998766188@highgo.ca

src/test/regress/expected/float4-misrounded-input.out

@@ -24,6 +24,14 @@ INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70');
 ERROR:  "-10e-70" is out of range for type real
 LINE 1: INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70');
                                            ^
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e70'::float8);
+ERROR:  value out of range: overflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e70'::float8);
+ERROR:  value out of range: overflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e-70'::float8);
+ERROR:  value out of range: underflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70'::float8);
+ERROR:  value out of range: underflow
 INSERT INTO FLOAT4_TBL(f1) VALUES ('10e400');
 ERROR:  "10e400" is out of range for type real
 LINE 1: INSERT INTO FLOAT4_TBL(f1) VALUES ('10e400');

src/test/regress/expected/float4.out

@@ -24,6 +24,14 @@ INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70');
 ERROR:  "-10e-70" is out of range for type real
 LINE 1: INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70');
                                            ^
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e70'::float8);
+ERROR:  value out of range: overflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e70'::float8);
+ERROR:  value out of range: overflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e-70'::float8);
+ERROR:  value out of range: underflow
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70'::float8);
+ERROR:  value out of range: underflow
 INSERT INTO FLOAT4_TBL(f1) VALUES ('10e400');
 ERROR:  "10e400" is out of range for type real
 LINE 1: INSERT INTO FLOAT4_TBL(f1) VALUES ('10e400');

src/test/regress/sql/float4.sql

@@ -16,6 +16,11 @@ INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e70');
 INSERT INTO FLOAT4_TBL(f1) VALUES ('10e-70');
 INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70');
 
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e70'::float8);
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e70'::float8);
+INSERT INTO FLOAT4_TBL(f1) VALUES ('10e-70'::float8);
+INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e-70'::float8);
+
 INSERT INTO FLOAT4_TBL(f1) VALUES ('10e400');
 INSERT INTO FLOAT4_TBL(f1) VALUES ('-10e400');
 INSERT INTO FLOAT4_TBL(f1) VALUES ('10e-400');