I downloaded latest recommend build for 1.5.2, ran install.cmd, then recompile.bat, and got compilation errors:

 

== MCP 7.51 (data: 7.51, client: 1.5.2, server: 1.5.2) ==
"scalac" is not found on the PATH.  Scala files will not be recompiled
# found ff, ff patches, srgs, name csvs, doc csvs, param csvs, renumber csv, ast
yle, astyle config
== Recompiling client ==
> Cleaning bin
> Recompiling
'"C:\Program Files\Java\jdk1.8.0\bin\javac" -encoding UTF-8 -Xlint:-options -dep
recation -g -source 1...' failed : 1

== ERRORS FOUND in JAVA CODE ==

src\minecraft\net\minecraft\client\entity\EntityPlayerSP.java:21: warning: [depr
ecation] ISidedInventory in net.minecraftforge.common has been deprecated
import net.minecraft.client.particle.EntityPickupFX;
                        ^

src\minecraft\net\minecraft\tileentity\TileEntityFurnace.java:502: warning: [dep
recation] getSizeInventorySide(ForgeDirection) in ISidedInventory has been depre
cated
    public int getSizeInventorySide(ForgeDirection side)
               ^

src\minecraft\net\minecraft\tileentity\TileEntityFurnace.java:485: warning: [dep
recation] getStartInventorySide(ForgeDirection) in ISidedInventory has been depr
ecated
    public int getStartInventorySide(ForgeDirection side)
               ^

src\minecraft\net\minecraft\item\Item.java:1118: warning: [deprecation] IArmorTe
xtureProvider in net.minecraftforge.common has been deprecated
        return isArmorProvider ? ((IArmorTextureProvider)this).getArmorTextureFi
le(stack) : null;
                                   ^

src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:332: error: cannot f
ind symbol
        if (doGen && this.randomGenerator.nextInt(4) == 0)
            ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:340: error: cannot f
ind symbol
        if (doGen && this.randomGenerator.nextInt( == 0)
            ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:364: error: cannot f
ind symbol
        doGen = TerrainGen.decorate(currentWorld, randomGenerator, chunk_X, chun
k_Z, PUMPKIN);
        ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:365: error: cannot f
ind symbol
        if (doGen && this.randomGenerator.nextInt(32) == 0)
            ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:381: error: cannot f
ind symbol
        doGen = TerrainGen.decorate(currentWorld, randomGenerator, chunk_X, chun
k_Z, LAKE);
        ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\world\biome\BiomeDecorator.java:382: error: cannot f
ind symbol
        if (doGen && this.generateLakes)
            ^

  symbol:   variable doGen
  location: class BiomeDecorator
src\minecraft\net\minecraft\src\ModLoader.java:632: warning: [deprecation] regis
terBlock(Block) in GameRegistry has been deprecated
        GameRegistry.registerBlock(block);
                    ^

src\minecraft\net\minecraft\src\ModLoader.java:643: warning: [deprecation] regis
terBlock(Block,Class<? extends ItemBlock>) in GameRegistry has been deprecated
        GameRegistry.registerBlock(block, itemclass);
                    ^

src\minecraft\net\minecraft\world\gen\ChunkProviderHell.java:524: error: cannot
find symbol
        doGen = TerrainGen.decorate(worldObj, hellRNG, k, l, SHROOM);
        ^

  symbol:   variable doGen
  location: class ChunkProviderHell
src\minecraft\net\minecraft\world\gen\ChunkProviderHell.java:525: error: cannot
find symbol
        if (doGen && this.hellRNG.nextInt(1) == 0)
            ^

  symbol:   variable doGen
  location: class ChunkProviderHell
src\minecraft\net\minecraft\world\gen\ChunkProviderHell.java:533: error: cannot
find symbol
        if (doGen && this.hellRNG.nextInt(1) == 0)
            ^

  symbol:   variable doGen
  location: class ChunkProviderHell
9 errors
6 warnings
==================

!! Can not find server sources, try decompiling !!

 

What should I do to fix that?

Read this:

http://www.minecraftforge.net/forum/index.php/topic,10996.msg56337.html#msg56337

Have you ran decompile.bat?