fix(plan): evaluate REPLACE ... SET RHS column references as DEFAULT(col)

[ck89119]

What type of PR is this?

• BUG

Which issue(s) this PR fixes:

issue #24945

What this PR does / why we need it:

Subtask of #24918 (section 1). For REPLACE ... SET col = col + 1, MySQL treats the RHS reference to a target-table column as DEFAULT(col), not the current conflicting row value. Missing columns also fall back to their defaults, matching normal REPLACE insert semantics.

Before this PR, MatrixOne reported invalid input: ambiguous column reference 'v' and left the old row unchanged:

create table t_set(id int primary key, v int default 5, note varchar(20) default 'd');
insert into t_set values (1,10,'old');
replace into t_set set id = 1, v = v + 1;
select * from t_set;   -- expected 1 | 6 | d

Root cause

The parser lowers REPLACE ... SET a = x, b = y to tree.Replace{Columns, Rows: ValuesClause}, i.e. the same AST shape as the VALUES form. When buildValueScan binds the value expressions it uses a DefaultBinder whose bind context is nil, so any column reference hits the b.ctx == nil branch in baseBindColRef and fails with "ambiguous column reference".

Fix

• Add an IsSetFormat marker to tree.Replace, set only in the SET grammar branch, so the SET-only semantics can be distinguished from the VALUES form (which still rejects column references, matching MySQL).
• Add a ReplaceValueBinder that resolves every RHS column reference to that column's DEFAULT(col) expression. SET-form value binding is routed through it via a new colRefAsDefault flag threaded from bindReplace → initInsertReplaceStmt → buildValueScan. INSERT and the VALUES form are unchanged.

Tests

• Unit tests: ReplaceValueBinder (default value resolution, case-insensitive lookup, unknown column error, unsupported bindings) — 100% coverage of the new file; planner test TestReplaceSetColRefAsDefault.
• BVT: new cases in dml/replace/replace.test covering provided/omitted columns and references to other columns' defaults (set id=1,v=v+1→1|6|d, set id=2,v=v*2→2|10|d, set id=1,a=b+1→1|8|7); verified with mo-tester (198/198), replace_statement 50/50 with no regression.

🤖 Generated with Claude Code

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