Extend pg_cast castimplicit column to a three-way value; this allows us

to be flexible about assignment casts without introducing ambiguity in
operator/function resolution.  Introduce a well-defined promotion hierarchy
for numeric datatypes (int2->int4->int8->numeric->float4->float8).
Change make_const to initially label numeric literals as int4, int8, or
numeric (never float8 anymore).
Explicitly mark Func and RelabelType nodes to indicate whether they came
from a function call, explicit cast, or implicit cast; use this to do
reverse-listing more accurately and without so many heuristics.
Explicit casts to char, varchar, bit, varbit will truncate or pad without
raising an error (the pre-7.2 behavior), while assigning to a column without
any explicit cast will still raise an error for wrong-length data like 7.3.
This more nearly follows the SQL spec than 7.2 behavior (we should be
reporting a 'completion condition' in the explicit-cast cases, but we have
no mechanism for that, so just do silent truncation).
Fix some problems with enforcement of typmod for array elements;
it didn't work at all in 'UPDATE ... SET array[n] = foo', for example.
Provide a generalized array_length_coerce() function to replace the
specialized per-array-type functions that used to be needed (and were
missing for NUMERIC as well as all the datetime types).
Add missing conversions int8<->float4, text<->numeric, oid<->int8.
initdb forced.

src/include/nodes/primnodes.h

@@ -10,7 +10,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: primnodes.h,v 1.67 2002/09/04 20:31:44 momjian Exp $
+ * $Id: primnodes.h,v 1.68 2002/09/18 21:35:24 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -139,6 +139,30 @@ typedef struct RangeVar
  * ----------------------------------------------------------------
  */
 
+/*
+ * CoercionContext - distinguishes the allowed set of type casts
+ *
+ * NB: ordering of the alternatives is significant; later (larger) values
+ * allow more casts than earlier ones.
+ */
+typedef enum CoercionContext
+{
+	COERCION_IMPLICIT,			/* coercion in context of expression */
+	COERCION_ASSIGNMENT,		/* coercion in context of assignment */
+	COERCION_EXPLICIT			/* explicit cast operation */
+} CoercionContext;
+
+/*
+ * CoercionForm - information showing how to display a function-call node
+ */
+typedef enum CoercionForm
+{
+	COERCE_EXPLICIT_CALL,		/* display as a function call */
+	COERCE_EXPLICIT_CAST,		/* display as an explicit cast */
+	COERCE_IMPLICIT_CAST,		/* implicit cast, so hide it */
+	COERCE_DONTCARE				/* special case for pathkeys */
+} CoercionForm;
+
 /*
  * Expr
  */
@@ -194,6 +218,7 @@ typedef struct Func
 	Oid			funcid;			/* PG_PROC OID of the function */
 	Oid			funcresulttype; /* PG_TYPE OID of result value */
 	bool		funcretset;		/* true if function returns set */
+	CoercionForm funcformat;	/* how to display this function call */
 	FunctionCachePtr func_fcache;		/* runtime state, or NULL */
 } Func;
 
@@ -460,6 +485,7 @@ typedef struct RelabelType
 	Node	   *arg;			/* input expression */
 	Oid			resulttype;		/* output type of coercion expression */
 	int32		resulttypmod;	/* output typmod (usually -1) */
+	CoercionForm relabelformat;	/* how to display this node */
 } RelabelType;