Index: src/expr.c
==================================================================
--- src/expr.c
+++ src/expr.c
@@ -3530,11 +3530,23 @@
         return iReg;
       }
       if( iTab<0 ){
         if( pParse->iSelfTab<0 ){
           /* Generating CHECK constraints or inserting into partial index */
-          return pExpr->iColumn - pParse->iSelfTab;
+          assert( pExpr->y.pTab!=0 );
+          assert( pExpr->iColumn>=XN_ROWID );
+          assert( pExpr->iColumn<pExpr->y.pTab->nCol );
+          if( pExpr->iColumn>=0
+            && pExpr->y.pTab->aCol[pExpr->iColumn].affinity==SQLITE_AFF_REAL
+          ){
+            sqlite3VdbeAddOp2(v, OP_SCopy, pExpr->iColumn - pParse->iSelfTab,
+                              target);
+            sqlite3VdbeAddOp1(v, OP_RealAffinity, target);
+            return target;
+          }else{
+            return pExpr->iColumn - pParse->iSelfTab;
+          }
         }else{
           /* Coding an expression that is part of an index where column names
           ** in the index refer to the table to which the index belongs */
           iTab = pParse->iSelfTab - 1;
         }

Index: test/check.test
==================================================================
--- test/check.test
+++ test/check.test
@@ -121,10 +121,15 @@
     CREATE TABLE t2(
       x INTEGER CONSTRAINT one CHECK( typeof(coalesce(x,0))=="integer" ),
       y REAL CONSTRAINT two CHECK( typeof(coalesce(y,0.1))=='real' ),
       z TEXT CONSTRAINT three CHECK( typeof(coalesce(z,''))=='text' )
     );
+    CREATE TABLE t2n(
+      x INTEGER CONSTRAINT one CHECK( typeof(coalesce(x,0))=="integer" ),
+      y NUMERIC CONSTRAINT two CHECK( typeof(coalesce(y,0.1))=='real' ),
+      z TEXT CONSTRAINT three CHECK( typeof(coalesce(z,''))=='text' )
+    );
     PRAGMA writable_schema = 0;
   }
 } {}
 do_test check-2.2 {
   execsql {
@@ -144,13 +149,21 @@
   catchsql {
     INSERT INTO t2 VALUES(1.1, NULL, NULL);
   }
 } {1 {CHECK constraint failed: one}}
 do_test check-2.5 {
+  # The 5 gets automatically promoted to 5.0 because the column type is REAL
   catchsql {
     INSERT INTO t2 VALUES(NULL, 5, NULL);
   }
+} {0 {}}
+do_test check-2.5b {
+  # This time the column type is NUMERIC, so not automatic promption to REAL
+  # occurs and the constraint fails.
+  catchsql {
+    INSERT INTO t2n VALUES(NULL, 5, NULL);
+  }
 } {1 {CHECK constraint failed: two}}
 do_test check-2.6 {
   catchsql {
     INSERT INTO t2 VALUES(NULL, NULL, 3.14159);
   }
@@ -193,10 +206,11 @@
 } {1 {CHECK constraint failed: x_two}}
 do_test check-2.cleanup {
   execsql {
     DROP TABLE IF EXISTS t2b;
     DROP TABLE IF EXISTS t2c;
+    DROP TABLE IF EXISTS t2n;
   }
 } {}
 
 ifcapable subquery {
   do_test check-3.1 {

Index: test/indexexpr1.test
==================================================================
--- test/indexexpr1.test
+++ test/indexexpr1.test
@@ -454,7 +454,31 @@
   CREATE TABLE t0(c0);
   INSERT INTO t0(c0) VALUES (0);
   CREATE INDEX i0 ON t0(NULL > c0) WHERE (NULL NOT NULL);
   SELECT * FROM t0 WHERE ((NULL IS FALSE) IS FALSE);
 } {0}
+
+# 2019-09-02 https://www.sqlite.org/src/tktview/57af00b6642ecd6848
+# When the expression of an an index-on-expression references a
+# table column of type REAL that is actually holding an MEM_IntReal
+# value, be sure to use the REAL value and not the INT value when
+# computing the expression.
+#
+do_execsql_test indexexpr-1800 {
+  DROP TABLE IF EXISTS t0;
+  CREATE TABLE t0(c0 REAL, c1 TEXT);
+  CREATE INDEX i0 ON t0(+c0, c0);
+  INSERT INTO t0(c0) VALUES(0);
+  SELECT CAST(+ t0.c0 AS BLOB) LIKE 0 FROM t0; 
+} {0}
+do_execsql_test indexexpr-1810 {
+  SELECT CAST(+ t0.c0 AS BLOB) LIKE '0.0' FROM t0; 
+} {1}
+do_execsql_test indexexpr-1820 {
+  DROP TABLE IF EXISTS t1;
+  CREATE TABLE t1(x REAL);
+  CREATE INDEX t1x ON t1(x, +x);
+  INSERT INTO t1(x) VALUES(2);
+  SELECT +x FROM t1 WHERE x=2;
+} {2.0}
 
 finish_test